Discovering Darwin

In this final episode of Season 5, Sarah, Mark, and James discuss the last chapters from Lucy Cooke's book Bitch: On the female of the species. Sarah described the sex lives of barnacles and encouraged us to watch the Green Porno episode that illustrates the impressive size of a barnacle penis. Image from https://bodegahead.blogspot.com/2017/06/a-long-reach.htmlThe conversation considered why Charles Darwin did not include barnacles in his Descent of Man, and Selection in Relation to Sex. Sarah suggested it would not fit nicely in his narrative on male and female roles in sexual selection. We then discussed how clown fish, which can shift their sexual identity from male to female, challenge the notions of sexual identity. Photo: Amanda Cotton/Coral Reef Image BankMark recounted Lucy Cooke's biologically accurate retelling of Finding Nemo which results in a story that would not get a G rating.  James questions if the term Gender is only relevant to humans, since we seem consumed with identity, and in the animal world, gender is meaningless as are terms like masculine and feminine. We then speculated how a modern Charles Darwin would integrate these diverse views of sexual identity and sexual strategies into a more inclusive theory of sexual selection.

In this episode Sarah, Mark and James continue their discussion of the book Bitch by Lucy Cooke where they explore menopause in humans and non-human animals and discuss those animals that have forwent males when they reproduce. The first conversation explored how orcas are an unusual mammal in that the males do not disperse from their mother's pod, but instead they retain a close relationship with their mothers. The ultimate momma's boy. Sarah discussed the various hypothesis for why women would actually go through menopause, and why it is an evolutionary puzzle. One of the hypothesis that Sarah thought had traction was the fact that human women at birth reduce their one million oocytes to about 300,000 at birth, and the number and quality of eggs continue to decline with age. The oocytes of a human female in stasis awaiting the monthly opportunity to develop into a fertile egg.We discussed why it is the female orca that experiences menopause and not the males. We finished the podcast discussing single sex albatross pairs who successfully rear offspring every year. James discussed seeing these birds raising their single offspring in the yards of a suburban neighborhood. Humans have encroached on much of the historical nesting sites of the albatross on the Hawaiian islands but Nevertheless, she persisted. Here is a picture of a baby albatross James took on Kauai where it is manipulating its parents by maintaining the baby downy feathers on its head while the adult feathers are on the rest of the body. We finished the podcast discussing the parthenogenic Mourning geckos that have colonized many of the islands of the Pacific since they can reproduce asexually. Virgin births have been observed in many chordates except in mammals. We discussed why that may be.A Mourning Gecko James photographed when doing field work in Kauai.Opening and closing music is "May" by Jared C. Balogh.Interlude music Confessions by Sudan Archives 

 In this episode Sarah, Mark, and James continue their coverage Bitch by Lucy Cooke. We discussed systems where female aggression was common and the subjugation of other females and males was done by "alpha" females.  We were surprised to learn how murderous and violent naked mole rats and sweet little meercats could be. Photo from Akron ZooNaked mole rats are eusocial mammals where a dominant female is the sole reproducer in the colony and others help rear the young. Here is a photo of a queen rat with her newborn pubs and other females assisting in their care. Do not be fooled by the serene nature of this image, those helper females are violently coerced into their roles.Photo from https://lsc.org/news-and-social/news/our-naked-mole-rats-had-babiesagainMeercats are also a fossorial social mammal that is ruled ruthlessly by the dominant female. The play of meercats often mimics fighting, which is always a constant possibility in their tight knit clan.The second half of the discussion focused on female dominant systems that rely more on alliances and social bonding to create group coherence. Ring tailed lemurs and bonobo chimpanzees were the classic system we discussed. At the end we tried to make sense of how ecology, physiology, and culture might be influencing a social system being matriarchal or patriarchal. Sarah noted that the males in these female dominant social systems reminded her of Ken in the movie Barbie. Opening and closing music is "May" by Jared C. Balogh.Interlude music My Humps by the Black Eyed Peas   

We continue our discussion of Lucy Cook's book entitled Bitch: On the female of the species focusing on chapters 5 & 6 which covered variation in female genitalia, the evolution of the human penis,  and maternal care. We spent some time talking about the baculum, a bone that is found in the penis of many mammals, but not in humans. Sarah described how intricately shaped the baculum of squirrels can be, as evident in the image below. From Bacula of North American Mammals by W. H. Burt, 1960Sarah also discussed a novel hypothesis presented by Jakovlic'  that proposes and explanation for the loss of human baculum through male-male aggression. James wondered why human copulation lasts so long? What is the point of all that thrusting for minutes on end?  We explored a couple of hypothesis that have been proposed to explain the exuberant level of pelvic thrusting typical in human copulation. James encouraged our listeners to look at the NSFW artwork of Jamie McCartney, a sculpture and photographer who has created a large portfolio of casts of penises and vaginas, and other secondary sexual characteristics, which clearly represent the variability in human genitalia. The second part of the podcast explored the myth of maternal care and how opposing neurological process can explain aggression towards babies or care and protection of babies. We explored how these process could help explain post-partum depression and how the modern medical process in child birth may interfere with the evolved bonding process that requires specific tactile, auditory, and olfactory cues shared between the mother and newborn. Opening and closing music is "May" by Jared C. Balogh.Interlude music was Detachable Penis from King Missile.  

 In this episode we continue our conversation based upon Chapters 3 & 4 of Lucy Cook's book Bitch: on the female of the species. We started off the conversation doing a deep dive on the famous Bateman experiment that purported to reveal 3 principles concerning variation in male and female reproductive success and how those differences drive sexual selection. After reviewing the experiments and what they were reported to show, Sarah then discussed some more recent papers that closely re-analyzed the original 1948 experiment and how that revealed critical flaws and biases in the study which weakens the strength of its conclusion.   We were left with thinking it is more Bateman Hypothesis than Bateman's Principles. Once we established that it is not correct to characterize females as being coy and unwilling to mate more than once, we explored the reasons why females would exhibit a level of promiscuity that rivals that expected from males. We discussed the orgasm as a feature in sexual activity and how scientists have tried to characterize this physiological response in other non-human primates. Image of O face adapted from drawing in Bitch from Chevalier-Skolnikoff's research.We had a spirited conversation about the evolution of the female orgasm and how it might influence females seeking multiple mates. We ended the podcast with a discussion of sexual cannibalism. We explored the reasons why, in some species of spiders, the males are so much smaller than the adult females which facilitates her eating the male. Although killing and eating a potential mate seems maladaptive, we discussed the various reasons why it may be adaptive for the female and for the male to kill or be killed. Post mating cannibalism in a web building spider. Image from Schneider 2014 The opening theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY Interlude musicGirls Just Want To Have Fun. Song by Cyndi LauperManeater. Song by Hall & Oats

We have returned from a long hiatus to discuss a wonderful book entitled Bitch: On the Female of the Species by Lucy Cooke. Sarah asked James and Mark to read this book that gives an updated look at Darwin's original model of sexual selection, a topic we covered extensively in Season 4. In this episode we cover the introduction and first 2 chapters of the book.In our conversation about the book, we discuss how Darwin's stereotypical, and simplistic. views of male and female roles in mating and reproduction have persisted 150 years later. As Sarah says, we are still suffering from the hangover Darwin's misogyny. Chapter one of the book does a great job challenging the simplistic notion of what "is a female?", and we explore that topic in detail. Mark was enamored with the existence of gynandromorphs (gyn=female, andro=male, morph=form), organisms that exhibit both male and female phenotypic structures. This led us to discuss the difference between sex and gender and why the simplistic view, often exposed in popular culture of late, of there being only 2 sexes, is incorrect and ignores actual biology. Image taken from https://www.eriebirdobservatory.org/ebo-blog/2021/2/21/a-second-bilateral-gynandromorph-northern-cardinal-in-northwest-pennsylvaniaWe also discuss how stereotypical gender roles influence how biologists interpret the behaviors they observed which often leads to misunderstanding and faulty interpretations. We encourage our listeners to read along with us, as we plan to discuss Chapters 3 & 4 next episode. Lucy Cooke (Photo: David Dunkerley)Here is another example of gynandromorphs, but in butterflies.Image from https://www.earth.com/news/gynandromorphs-half-male-half-female/The opening theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY     Interlude musicBitch Song by Meredith BrooksSage Grouse calls were from Greater Sage-grouse strut display https://www.youtube.com/watch?v=m0M8pZnNlnI

In this final episode of Season 4, Mark, Sarah, and James finally critiqued Darwin's analysis of secondary sexual characteristics in humans and his clumsy attempt to apply his model of sexual selection in explaining the diversity of forms in what Darwin called "races" and we call geographically distinct phenotypes (GDPs). We found that Chapters 19 & 20 of Descent of Man distilled and concentrated Darwin's most ethnocentric and sexist observations and pseudo-scientific explanations concerning the differences between the sexes and GDPs. Image from Wilson, Miller, and Crouse (2017)Sarah made the argument that human sexual dimorphism, differences in size and body form of males versus females, is the smallest of all seen in extant primates. Sarah questioned why Darwin tried to assign those slight differences to sexual selection. James made the argument that there are two categories of traits that Darwin was discussing. James referred to the physical traits, like hair color, skin color, height, facial shape, etc. are intrinsic traits you inherit genetically. Humans also exhibit extrinsic traits, hair styles, piercings, tattoos, clothing, etc. which you inherit culturally. Mark explained the complexity of beauty and why attraction and beauty are two different issues. We explored how specific standards of beauty are locally determined and how how diverse they can be across the globe. Both James and Sarah independently concluded that Darwin's model of sexual selection was not sufficient in explaining the creation of the great diversity of human forms seen between the geographically distinct phenotypes around the world. Sarah invoked founder effects and genetic drift, non selective processes, in creating genetically distinct populations that were then acted upon by local selective pressures, both from the environment and within the social group. It is through those processes Sarah thought created the geographically distinct phenotypes, and not through sexual selection. James agreed and thought that selection at the group level, where everyone in the social group, enforced phenotypic norms on others through infanticide and cultural practices of shunning or killing undesirables created the diversity of forms seen among the GDPs.  Sarah and James' models do not require the extreme level of sexual selection and polygyny required in Darwin's model to shift the phenotype of the entire population. Also, the social cohesion model of selection can allow for rapid shifts in the phenotype as the entire social group enforces the phenotypic norms instead of just the mating male and who he selects to mate with. The opening theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY     Interlude musicYou are so beautiful - Joe Cocker (1974)I'm too sexy - Right Said Fred (1992)     

 After a long COVID induced hiatus, we have returned to tackle the meaty middle of Charles Darwin's magnum opus The Descent of Man. It was actually most of Volume 2, three hundred and nineteen pages of anecdotes, observations, wild conjecture, and chuck'splaining his crazy system of inheritance. The dense plodding Victorian prose was diluted, a bit, by the amazing woodcut prints of beetles, fish, lizards, exotic birds whose feathers were stolen by Victorian women, and ornamented antelopes and other mammals. Human female adorned with decorative feathers stolen from birdsMark covered the fish, amphibians, and reptiles, since James forgot to assign the invertebrates, we did not discuss the myriad beetle examples Darwin discussed. However, Mark was impressed with the ways in which fish, during the breeding season, become so brightly colored. We mentioned a local fish, the male rainbow darter, which is quite striking during the spring breeding season. Mark was surprised to learn that there is no such thing as a fish and Sarah encouraged him to read Why Fish Don't Exist: A Story of Loss, Love, and the Hidden Order of Life – by Lulu MillerRainbow darter maleMark expressed his disappointment in the lack of sexual dimorphism in snakes, an animal group he has an inordinate fondness for. Although we did not discuss the invertebrates, James brought up the interesting sex determination system in slipper shell molluscs (pictured below) and how the top individual becomes the male, and all the ones below shift to be female. James tackled the immense bird section and offered a variety of hypothesis why the males of a species may look different than the females, in addition to Darwin's model of sexual selection and female choice. We also discussed the unique sex chromosome system in birds and how that is opposite of what we see in mammals and how some scientists believe it helped accelerate and magnify sexual dimorphism in birds. Fig. 47. Paradisea Papuana (T. W. Wood).Sarah covered sexual dimorphism in mammals and noted that Darwin believed most of that dimorphism was created through male-male battles for access to females and less about female choice. We had a lengthy discussion of antlers and horns and how they sometimes show up in both sexes but often is only found on the males. Sarah also discuss African lion manes and how they vary in shape and color where the darkest mane is the one most successful in fights and securing mates but there are costs with having the mane. A lion with a very dark maneWe also discussed the odd stotting behavior of some ungulates, as shown in the gif below. The opening theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY Interlude music Fat Caps by Jason Shawhttps://freemusicarchive.org/music/Jason_Shaw/Audionautix_Tech_Urban_Dance/TU-FatCaps/Love Cats by the Cure

 In this episode we dive into Chapter 8 from Darwin's Descent of Man. James incorrectly attributed this chapter to the end of Volume I of the two volume set but it is actually the first chapter of Volume II, which makes more sense given its dramatic shift in focus and topic. Sarah tried to get us to differentiate between adaptive traits that come about from sexual selection with those that come about from natural selection.  Photo from https://rollingharbour.com/2017/02/14/bluehead-wrasse-private-life-laid-bare/We spent some time discussing the difference between sex-linked traits, like calico cat color,  and sexually selected traits like the giant antlers on the extinct Irish Elk.  James presented just a few hypothesis that have been proposed to explain female choice of traits and why those traits that females seem to prefer are often opposed by natural selection. It is hard to be a red male cardinal in the dead of winter. Sarah suggested interested listeners read The Evolution of Beauty by Richard O. Prum to learn how to differentiate the products of sexual and natural selection. We had a robust discussion about sex and gender and what Darwin knew at the time and what he should have acknowledged about the lack of binary distinction in the sexes. Mark realized he misspoke when he said that the rate of disorders of sexual development are around 10%. Data suggests that it occurs more like  (1:2500–5000 live births) whereas gender dysphoria is reported to occur around 0.002-0.014%. The bluehead wrasse is a wonderful organism that challenges the simple-minded view that your sex is determined at birth. https://www.bbc.com/news/av/uk-northern-ireland-45449128Sarah also encouraged us to watch some Green Porno to learn more details about the sex lives of non-human animals. You can see it hereThe opening theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY Interlude music is Alberta Hunter singing My handy man ain't handy no more from her Amtrak Blues album.

 image from:https://www.artsales.com/ARTistory/angelic_journey/index.htmlIn this bonus episode we return to our conversation with our favorite ex-monk philosopher friend Dr. Jack Furlong where he discusses whether angels, as described in scripture, could actually be moral.  We then briefly discuss the Yale baby lab where clever behavioral experiments are done on human babies to see how early they exhibit cognitive decision making. We hope to be back in the studio to record a complete episode out soon. 

 In this episode we finally confront Chapter 7 of Descent of Man,  entitled On the Races of Man. In this  chapter Darwin discusses the races of humans and outlines the scientific arguments of the time that questioned if humans are more than one species.  These arguments, of course, were based upon racist European views of the people from the lands their countries had colonized. Race is a social construct, not a biological identity, and we discussed why that is the case in this episode.  https://angelicadass.com/photography/humanae/James Wagner's daughter participated in this awesome art project and she is included in the images above.At one point we noted that Darwin reintroduced the idea of a range of varieties of organisms that can interbreed along a geographical range, but the ends of the ranges were reproductively isolated. We introduced that idea, often called a ring species, in Season 1 Episode 3, which can be found here. Sarah loves her ectoparasites and their evolution and discussed Darwin's 30 year obsession with that issue. Here is a link to a wonderful series of articles about Descent of Man and that obsession.The opening theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY Interlude music is We are Many, We are One a song from Up With People, a group of musicians who "stage song and dance performances promoting themes such as religion, racial equality, and positive thinking." Our own Mark Jackson played trumpet with Up With People before pursuing his career in psychology.

Mark, Sarah, and James discuss Chapter 6 of Charles Darwin's Descent of Man. In this chapter Darwin unequivocally declares humans evolved from ancestral primate stock and that event occurred in Africa. We discussed how prescient Darwin was in interpreting the biology and scant fossil record in determining human relationship in the evolutionary tree. (Image credit: Nick Hobgood/Wikimedia Commons)We discussed at length this problematic paragraph:The great break in the organic chain between man and his nearest allies, which cannot be bridged over by any extinct or living species, has often been advanced as a grave objection to the belief that man is descended from some lower form; but this objection will not appear of much weight to those who, convinced by general reasons, believe in the general principle of evolution. Breaks incessantly occur in all parts of the series, some being wide, sharp and defined, others less so in various degrees; as between the orang and its nearest allies—between the Tarsius and the other Lemuridæ—between the elephant and in a more striking manner between the Ornithorhynchus or Echidna, and other mammals. But all these breaks depend merely on the number of related forms which have become extinct. At some future period, not very distant as measured by centuries, the civilised races of man will almost certainly exterminate and replace throughout the world the savage races. At the same time the anthropomorphous apes, as Professor Schaaffhausen has remarked, will no doubt be exterminated. The break will then be rendered wider, for it will intervene between man in a more civilised state, as we may hope, than the Caucasian, and some ape as low as a baboon, instead of as at present between the negro or Australian and the gorilla.After that awkward discussion we finished with the notion that our ancestor probably looked like a sea squirt. Here is the episode that Sarah referenced on the economics of Darwin's voyage - it was called to Drawn a BillThe opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.1st interlude music was Mr. Smith - Happy Dance. https://freemusicarchive.org/music/mr-smith2nd Interlude musicIt's a long way to Amphioxus by Sam Hinton https://www.youtube.com/watch?v=B0egWbwErRQ

In this episode we enlist a different Furlong, Dr. Jack Furlong, to help us untangle morality and determine if there really is such a thing as big M morality, as Sarah calls it.   Jack, after a very in depth explanation, says "No". Jack invokes the classic Trolley thought experiment to illustrate why various historical positions on morality stumble when confronted with the scenario and asks which big M morality system should be employed when resolving the trolley dilemma. Jack also challenges the view that morality in humans is either unique or exceptional. We also discussed how morality may show up in non-human animals and Jack cleared up for James the proper term to use when referring to more than a single octopus.  We also discussed if an octopus would have morality. https://www.theguardian.com/environment/2019/may/12/octopus-farming-unethical-and-threat-to-food-chainThe opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music ENCOMIUM by Evan Schaeffer Music Studios | https://soundcloud.com/evanschaefferMusic promoted by https://www.free-stock-music.comCreative Commons Attribution 3.0 Unported Licensehttps://creativecommons.org/licenses/by/3.0/deed.en_USThe Cure - Close to You

In Chapter 4 Darwin begins to sketch out his views on how complicated human behaviors, like sacrifice, empathy for others, and group defense would evolve when selection would favor us to act otherwise.Chapter 4 is entitled Comparison of the Mental Powers of Man and the Lower Animals - continued, but the short title at the top of the page is Moral Sense, which suggests what Darwin really thinks he is discussing. although he never clearly defines morality Mark shares with us a couple of definitions of morality and notes that Darwin hints at the idea that morality is actions that we feel we ought to do, not necessarily what we want to do. Later in the chapter Darwin entangles into the concept of morality ideas of choice, doing things that are not innate, and having a sense of what others expect of us, and us wanting to avoid disapprobation from our social group.We discussed altruistic and defensive behaviors exhibited in social animals and asked if those actions were actually moral. Here is an image of a baboon facing off a leopard to protect the baboon troop, is that action moral?James proposed of the idea that there is a set of morals that are independent of religion or culture but are based upon equality and fairness that all rationale people would agree upon. Sarah referred to this as capital M morality and rejected the notion. Mark stayed silent of the idea....Chapter 5 is where Darwin outlines his view that groups selection could explain the shift for moral behaviors, those behaviors that benefit the group at the cost to the individual. Darwin noted that- When two tribes of primeval man, living in the same country, came into competition, if (other circumstances being equal) the one tribe included a great number of courageous, sympathetic and faithful members, who were always ready to warn each other of danger, to aid and defend each other, this tribe would succeed better and conquer the other. Let it be borne in mind how all-important in the never-ceasing wars of savages, fidelity and courage must be. The advantage which disciplined soldiers have over undisciplined hordes follows chiefly from the confidence which each man feels in his comrades. Obedience, as Mr. Bagehot has well shewn, is of the highest value, for any form of government is better than none. Selfish and contentious people will not cohere, and without coherence nothing can be effected. A tribe rich in the above qualities would spread and be victorious over other tribes: but in the course of time it would, judging from all past history, be in its turn overcome by some other tribe still more highly endowed. Thus the social and moral qualities would tend slowly to advance and be diffused throughout the world.We discussed the strengths and weaknesses of group selection argument and also explored the conflicted tone Darwin used in these two Chapter. In these two chapters alone, Darwin used the term "savages" thirty-two times. In the entire text, Darwin used the term "savages" 187 times! We discussed what he meant by that term and considered modern alternative.In this episode Sarah, Mark, and James discuss Chapter 4 & 5 of Darwin's The Descent of Man.  Before we got started, James noted that Mark is the campus champion of Crokinole which he plays in his campus office on this board. Mark Jackson's office Crokinole championship arenaThe opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music is Overthrow by Shaolin Dub

 In this episode we discuss Chapter 3: The Mind from Darwin's Descent of Man. We are joined by a very special guest - Dr. Ellen Furlong from Illinois Wesleyan University who studies cognition in dogs. In this chapter Darwin spends some time going through a litany of traits that he associates with intelligence. His goal is to get the reader to recognize that humans, although very intelligent, are only different in degree and not in kind when compared to other animals. The list of traits Darwin thought indicated intelligence were:CuriosityImitationAttentionMemoryImaginationReasonProgressive ImprovementTools and weapon useAbstractionSelf-consciousnessLanguageSense of BeautyComplex emotions Belief in God, superstition, etc.Darwin started off the discussion clarifying the difference between instinct and intelligence and noted some researchers proposed that instinct and intelligence are an inverse ratio to each other, the more your behaviors are dictated by instinct the less intelligence, as defined by the traits above, you exhibited. Mark discussed instinct in humans when he was a special guest of the Podcast nearly 6 years ago from when we recorded this podcast. He was a special guest in October 2015 and we recorded this episode October 2021. You can find Mark's inaugural appearance here.Ellen explained how nest building behavior is different from other behaviors we may do without thinking and why nest building is an instinct and bike riding is not.Ellen made it clear that intelligence can only be compared within a species and in comparison to other individuals within a species. It is incorrect to make cross species comparisons when it comes to intelligence, since each species is a genius for its own domain. Ellen notes people love to make claims about how smart their dogs are, but they often ignore the failings of their dogs in those comparisons. Ellen noted a short essay she wrote about how dogs do love us has been very popular as people are very interested in knowing what is going on in the minds of their pets. We ended the conversation about the classic marshmallow test which purported to measure patience and delayed gratification in young children. Children were offered a single marshmallow and told if they waited and not eat it, they would be given a second one later. It is the idea that can we resist our desire for instant gratification now for some possible bigger gratification in the future. Ellen discussed her own efforts to replicate that experiment using dogs and a variety of treats.  Unfortunately COVID has disrupted her research.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music is "Who let the dogs out?" by the Baha Men 

  In this episode we discuss Chapter 1 of Descent of Man and are joined by a special guest - Evolutionary developmental (EvoDevo) biologist Dr. Belinda Sly. Darwin spends the chapter documenting how human bodies show the scars from evolution past. Darwin takes two approaches in convincing the reader that humans are modified from "lower forms". In one approach he discusses how humans share ailments, diseases, and parasites with other animals. The argument of homology. The second argument Darwin uses is cataloging the various rudimentary, vestigial, and nascent structures humans have and how they are present and useful in other animals.Sarah highlighted the homology argument that Darwin used - the fact that humans share diseases and parasites with other animals, showing the similarity of our bodies with other animals - by discussing the diversity of human lice - head, body, and pubic lice. After explaining the differences between each, Sarah helped us understand how they are used to identify important points in our evolutionary past, when we became hairless and when we adopted clothes. The strongest homology argument that Darwin presented was the similarity in form of vertebrate embryos and how the new technology of the time - microscopes - was increasing that dataset.  Dr. Belinda Sly discussed the different scientists of the time that were documenting embryo development - Karl Ernst von Baer and Ernst Haeckel. There is great similarity in embryo forms for various vertebrate animals, although Haeckel seems to have exaggerated those similarities in his illustrations. Belinda discussed the power of the comparison of embryos, and how they do give the best evidence of evolution via descent with modification but fall short of the old adage "ontogeny recapitulates phylogeny".The second line of argument Darwin discussed was the various rudimentary or vestigial structures we have that are of "absolutely useless faculty".  In particular he spent some time highlighting our restricted ability to use our panniculus carnosus muscles to move our skin as illustrated in this GIF of a horse twitching its skin to dislodge flies. In humans the ability is mostly restricted to our ability to move our eyebrows, but Darwin discussed some families ability to move their scalp and Sarah shared her "lamest super power ever" ability to slightly move her ears. The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.1st interlude music is Head Lice song https://www.youtube.com/watch?v=7us3ucQmrIE2nd interlude music is Black Bear Combo - Black Bear Kolo http://blackbearcombo.com/  

 https://commons.wikimedia.org/This is the first episode of Season 4 where we begin our exploration of Charles Darwin's Descent of Man, and Selection in Relation to Sex which was published in 1871. In this episode we explore how Darwin finally got around to discussing the evolution of humans, a topic he avoided in Origin of Species even though he told Alfred Wallace it was "...the highest & most interesting problem for the naturalist." In creating the book he relied on a wide array of scientists, citizen scientists, and bureaucrats in collecting the wide array of facts he uses to support his claim that humans are just another animal and we have evolved like any other organism. We discussed what the social, political, and scientific climate was like when Darwin was publishing this book and how it was received by his friends and enemies alike. https://www.darwinproject.ac.uk/henrietta-emma-darwinSarah introduced us to Henrietta Darwin, Charles's daughter who was influential in editing Descent of Man. We discussed the amazing University of Cambridge correspondence project where you can easily search the immense database of correspondences between Charles Darwin and other family members, scientists, friends, his publisher, and others, Follow this link if you wish to explore the site. Sarah reminded us of the tragic tale of the children who were on the Beagle when young Charles Darwin traveled the world. You can find that story told in detail in our first episode of Season 2 entitled Hot Coffee The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music is "Saulsalita Soul" by Mr. ruiZ

 By Photographer unidentified - MS Am 1092 (1185), Houghton Library, Harvard University, Public Domain, https://commons.wikimedia.org/w/index.php?curid=34246605In this final episode of Season 3 we actually do not talk about Darwin, but instead focus our attention to William James, a medical doctor, early psychologist, and philosopher who wrote about emotions about 20 years after Charles Darwin published The Expression of the Emotions in Man and Animals. Mark suggested we read James' views on emotion which he published first in his 1890 two volume set of his Principles of Psychology and then distilled in his single volume Psychology:Briefer Course. You can find reading editions of both books at the wonderful resource Project Gutenberg.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music Laid by James

 modified image from Bridgeman Art LibraryMark, Sarah, and James discuss the last technical chapter of Charles Darwin's The Expression of Emotions in Man and Animals, Chapter XIII:  Self Attention, Shame, Shyness, Modesty: Blushing. Mark Jackson's graduate research was on shame and guilt and he explained to us the difference between shame, guilt, embarrassment, and humiliation (a concept Darwin did not address) and why they are actually distinctly different emotions. In our discussion Mark explains why parents and teachers should not shame their children/students, but employ guilt, the gift that keeps on giving, if a change in behavior is what you seek.Darwin recognized blushing as a very distinct human behavior. In the chapter Darwin wrote:In most cases the face, ears and neck are the sole parts which redden; but many persons, whilst blushing intensely, feel that their whole bodies grow hot and tingle; and this shows that the entire surface must be in some manner affected. Blushes are said sometimes to commence on the forehead, but more commonly on the cheeks, afterwards spreading to the ears and neck We discussed the adaptive value of the blush as an honest signal that is exhibited in all humans, regardless of their skin color. Some of the studies we discuss indicated that when people see another blushing after being involved in a transgression or a mishap, the observer is more likely to give them sympathy or see them in a more positive light than if the person has a guilty or expression of shame without the blush.  Sarah discussed James' proclivity to blushing, and her warped sense of fun in making him blush. Some papers we referencedDijk, Corine, Peter J. De Jong, and Madelon L. Peters. "The remedial value of blushing in the context of transgressions and mishaps." Emotion 9.2 (2009): 287.Feinberg, Matthew, Robb Willer, and Dacher Keltner. "Flustered and faithful: Embarrassment as a signal of prosociality." Journal of personality and social psychology 102.1 (2012): 81.Jackson, Mark A. Distinguishing shame and humiliation. Diss. University of Kentucky, 1999.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music Too Shy by Kajagoogoo

 We discuss Chapter XII of the text The Expression of the Emotions in Man and Animals. In this chapter Darwin explores the expressions we associate with surprise, fear, terror, horror, and anxiety. The stereotypical expression of fear, as represented by the image above from the 1950's horror film franchises,  has both a physiological function and a signal function. We discuss the various arguments Darwin made about the reason your eyes are opened wide, your mouth held agape, your hands held up. In this chapter Darwin used both photographs from Duchenne and woodcuts from photographs to illustrate the unique expressions humans employ when exhibiting that emotion. Fig. 20. Terror. From a photograph by Dr. Duchenne.We discussed how these expressions often illicit aid from others. In addition to people responding to the visual signal of fear, research has indicated that we also respond to the smell of fear. James discussed a study (Chen, Katdare, & Lucas 2006) where sweat samples generated from individuals who were either neutral or experiencing fear, as induced from watching scary movies, would trigger differences in cognitive abilities in third parties who smelled the sweat and then were tested for word association. We had a robust conversation about the apparent gender differences in the expression of anxiety. One of the complexities of this issue is untangling social norms and how they alter anxiety expression from biological differences that may alter anxiety expression.    The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music opening theme to Jaws - John WilliamsChen, Denise, Ameeta Katdare, and Nadia Lucas. "Chemosignals of fear enhance cognitive performance in humans." Chemical senses 31.5 (2006): 415-423. McLean, Carmen P., and Emily R. Anderson. "Brave men and timid women? A review of the gender differences in fear and anxiety." Clinical psychology review 29.6 (2009): 496-505.

 Billy Idol and his trademark sneerIn this episode of Mark, Sarah, and James discuss Chapter XI from Darwin's text The Expression and Emotions in Man and Animals, 3rd edition. Sarah noted that this chapter was a potpourri of emotions, including: Scorn, Disdain, Contempt, Disgust, Jealousy, Envy, Avarice, Revenge, Suspicion, Deceit, Slyness, Guilt, Vanity, Conceit, Ambition, Pride, Humility, Helplessness, Impotence, Affirmation, *heavy sigh*...and Disapproval.Darwin's use of images in this chapter, to James, were not too convincing. Here is plate 1 in this chapter. Looks more like a silent film serial actor than a real expression of contempt.We compared the role of classic sneer expression in the modern place and how it has morphed into more subtle expressions or verbal components. James brought up the common expression Sarah Huckabee Sanders gave as one of the many press secretaries in the previous presidential administration. Her expression seemed to be a chimera of emotions- Contempt + Disdain + a dash of the two '-ceits'.     Notice that her clothes are different in each image, she employed this expression frequently.Mark explored the notion of disgust and explained how Darwin's narrowly applied use of disgust, an emotion associated only with tainted food, has now been expanded to include how we feel about social interactions and how the feeling of disgust may be the foundation of moral rules. We briefly mentioned the work of Jonathan Haidt and colleagues on this intriguing relationship between our concepts of disgust and how they relate to our ideas of moral rights and wrongs. If you want to see how you fair on the disgust scale visit this Yourmorals.org and take some of the questionnaires. Fascinating stuff.  We closed talking about the potpourri of emotions discussed in the end of the chapter and how the shrug,  ¯_(ツ)_/¯  and nodding yes in the affirmative and shaking your head no in the negative are not as universal as one would think, or Darwin would hope. The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music, as requested by Sarah, is Bloodhound Gang, Bad Touch

 In this episode we discuss both Chapters IX & X from Darwin's The Expression of the Emotions in Man and Animals. Chapter IX dealt with the interesting phenomenon of the frown - a telltale expression we exhibit when we are disappointed, sad, or confused. Darwin notes:"From these considerations, we may conclude that frowning is not the expression of simple reflection, however profound, or of attention, however close, but of something difficult or displeasing encountered in a train of thought or in action. Deep reflection can, however, seldom be long carried on without some difficulty, so that it will generally be accompanied by a frown".We discussed how the frown is an expression that rarely exhibits "emotional contagion" where others mirror the expression once they see it in someone else. Unlike smiles, which strangers can elicit into others about 20% of the time, frowning at strangers does not result in them frowning back. We discussed the evolutionary value of the frown and why it is exhibited in so many contexts. We spent a lot of the time discussing Hatred and Anger and the unique and specific expressions associated with those emotions. James mentioned a memorable image that came out the Black Lives Matter marches in Montana where an older white man exhibits all of the expression characteristics Darwin lists for those in anger. Spencer Schacht ABC FOX Montana"The mouth is commonly compressed, and there is almost always a frown on the brow. Instead of the frantic gestures of extreme rage, an indignant man unconsciously throws himself into an attitude ready for attacking or striking his enemy, whom he will perhaps scan from head to foot in defiance. He carries his head erect, with his chest well expanded, and the feet planted firmly on the ground. He holds his arms in various positions, with one or both elbows squared, or with the arms rigidly suspended by his sides. Darwin pg 242"Mark and Sarah discussed how anger is associated with change, and expressions of anger seem to exhibit "emotional contagion" but in reality it is often more of a result of positive feedback system, i.e., your anger feeds my anger which then feeds back to your anger. Mark discussed an interesting study by  Ceccarini and Caudke (2013) that explored how readily do we recognize an angry or happy face in a crowd. Based upon images of known facial expression they altered the images to remove elements of the individual to create generic genderless face with a range of emotions.With these images they could animate them to have changes in facial expression or they could show the still images within a montage of other expressions. They determined that humans are very good at quickly identifying both happy and angry expressions in a crowd, particularly when the face is opposite expression of the crowd. Recognition of angry faces was significantly faster than happy faces but the difference was only around 200 milliseconds faster showing that we are very sensitive to recognizing both happy or angry faces in a crowd of people exhibiting neutral or alternative expressions. There is a significant cost in exhibiting anger since the physiological changes associated with anger, increase in blood pressure, increase in heart rate, etc. are often linked to an increase in heart attacks. Darwin noted this in his book and modern research has focused on the role of expressions of anger and how management of anger can influence health outcomes.  Studies discussed in the podcast:Ceccarini, Francesco, and Corrado Caudek. "Anger superiority effect: The importance of dynamic emotional facial expressions." Visual Cognition 21.4 (2013): 498-540.Hinsz, Verlin B., and Judith A. Tomhave. "Smile and (half) the world smiles with you, frown and you frown alone." Personality and Social Psychology Bulletin 17.5 (1991): 586-592.Lench, Heather C., Thomas P. Tibbett, and Shane W. Bench. "Exploring the toolkit of emotion: What do sadness and anger do for us?." Social and Personality Psychology Compass 10.1 (2016): 11-25.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music was Big Beats Alternative by Sunsearch 

 In this episode of Discovering Darwin we tackle Chapter VIII - Joy, High Spirits, Love, Tender Feelings, Devotion in Darwin's book The Expression of the Emotions in Man and Animals. In this chapter Charles explores how we express ourselves when we are happy, in particular he discussed the two expressions associated with a happy mental state - smiling and laughing. Mark, Sarah and I explore what a "real" smile looks like, why we fake it sometimes, and why women more often fake it. Clearly a Duchenne "D" smileThe Duchenne smile is defined by the contraction of the obicular muscles that surround the eyes and the raising of the lips to expose the upper teeth. Darwin describes it as:Dr. Duchenne repeatedly insists that, under the emotion of joy, the mouth is acted on exclusively by the great zygomatic muscles, which serve to draw the corners backwards and upwards; but judging from the manner in which the upper teeth are always exposed during laughter and broad smiling, as well as from my own sensations, I cannot doubt that some of the muscles running to the upper lip are likewise brought into moderate action. The upper and lower orbicular muscles of the eyes are at the same time more or less contracted...Image from: https://www.earthslab.com/anatomy/orbicularis-oculi/Perfect for an audio podcast, we spent a long time discussing the value and accuracy of Plate III which was meant to illustrate various people in a state of happiness. Sarah thought the girl (bottom left, image 3) looked to be up to no good, she called her a minx!. We discussed how happy the man pictured on the right side of the page actually appeared to be. We also discussed laughter and how it may have evolved as a false alarm call. Laughter is found to be exhibited in other apes. Interestingly, the variation in the sounds apes like gorillas, chimpanzees, orangutans, bonobos, and humans make when being tickled follows the same pattern of relatedness seen in the phylogenetic tree based upon genetic relatedness. From Ross, Owren, and Zimmermann (2009)Papers we discussed:Ramachandran, Vilayanur S. "The neurology and evolution of humor, laughter, and smiling: the false alarm theory." Medical hypotheses 51.4 (1998): 351-354.Ross, Marina Davila, Michael J. Owren, and Elke Zimmermann. "The evolution of laughter in great apes and humans." Communicative & Integrative Biology 3.2 (2010): 191-194.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music was Laugh from Lotusland: A musical comedy by Ian Whitcomb

 Persons suffering from excessive grief often seek relief by violent and almost frantic movements, as described in a former chapter; but when their suffering is somewhat mitigated, yet prolonged, they no longer wish for action, but remain motionless and passive, or may occasionally rock themselves to and fro. The circulation becomes languid; the face pale; the muscles flaccid; the eyelids droop; the head hangs on the contracted chest; the lips, cheeks, and lower jaw all sink downwards from their own weight. Hence all the features are lengthened; and the face of a person who hears bad news is said to fall. [Charles Darwin. opening of Chapter VII, EEMA] In this episode we discussed Chapter VII - Low Spirits, Anxiety, Grief, Dejection, Despair. Although the title of the chapter covers a variety of emotions, we, following Darwin's lead, focused solely on grief. Darwin identified a group of muscles that are involved in creating the grief-stricken visage we are familiar in others. The inner ends of the eyebrows are raised, the outer ends depressed while the corners of the mouth are drawn downward. Overall the face takes on an elongated expression and the furrows in the brow take on an distinctive horse-shoe shape. In the podcast we discussed how the chapters we have read from Darwin's text Expression of the Emotions in Man and Animals so far reads more like a field guide, with textbook description of the facial muscles involved in exhibiting the expressions, than a intellectual analysis of the adaptive value of the emotions. Sarah, so far, has not been impressed. We hope that will come later in the text. We all agreed that Grief is an emotion associated with loss and we explored in the podcast how universal is that view of grief and are there other emotions associated with grief that are universal? Sarah introduced us to a paper that examined how universal emotional concepts were in terms of linguistics and if there is similarity in emotional meaning across cultures. In seems that cultures in close geographical location share a greater similarity in meaning for identified emotions than cultures that are separated by distance. It seems that there are universal emotions but what feelings that are associated with those emotional states are varied and often culturally defined.James questioned the adaptive value of adults exhibiting grief for the loss of non-related individuals. Sarah mentioned Neese's argument that we are expressing the loss of a known commodity - someone we have a strong relationship with that does not require accounting for altruistic behaviors - so their death is a loss felt as a loss of investment.   The paper discussed was:Jackson, Joshua Conrad, et al. "Emotion semantics show both cultural variation and universal structure." Science 366.6472 (2019): 1517-1522.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.The interlude music was from Hee Haw

 "The fact of tears not being shed at a very early age from pain or any mental emotion is remarkable, as, later in life, no expression is more general or more strongly marked than weeping."  pg 154 EEMA Charles Darwin. In this episode we explore Chapter VI: Suffering and Weeping where Darwin describes in excruciating detail the muscles involved in the crying face of infants and how tears are formed in the lacrimal glands. This chapter is the first one in the book to use photographic images to represent the expression of the emotions Darwin is describing. We discussed Plate 1 in detail and it can be seen here:Sarah discussed Duchenne's original photograph that Darwin showed people to see if they could recognize the emotion based upon the stimulation of specific facial muscles.  In the 3rd Edition of the book, Ekman includes the original photograph that was not actually in the earlier editions of the book.James discussed his amazement on where in his body tears are made, and where they go ultimately. The lacrimal glands reside above the eye and the tear duct, where James erroneously thought tears came from, is the location where tears drain into the back of your throat. We relied on a number of original research papers to help us understand the topic. Some of the papers we cited can be found here:Becht, Marleen C., and Ad JJM Vingerhoets. "Crying and mood change: A cross-cultural study." Cognition & Emotion 16.1 (2002): 87-101.Gračanin, Asmir, Lauren M. Bylsma, and Ad JJM Vingerhoets. "Why only humans shed emotional tears." Human Nature 29.2 (2018): 104-133.Oriá, Arianne P., et al. "Comparison of Electrolyte Composition and Crystallization Patterns in Bird and Reptile Tears." Frontiers in Veterinary Science 7 (2020): 574. Yong, Min Hooi, and Ted Ruffman. "Emotional contagion: Dogs and humans show a similar physiological response to human infant crying." Behavioural processes 108 (2014): 155-165.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Intermission music "Cryin" by Chris Isaak

In this episode we discuss Chapters 4 & 5 of Darwin's The Expression of the Emotions of Man and Animals, 3rd Definitive edition. Chapter 4 documented how animals use specific sounds and body postures to communicate their current emotional state. We explored how familiar we are to the sounds of domestic dogs and cats and the information they encode in their vocalizations. James was intrigued with the idea that early human language may have been more musical than expected. Mark spoke about the work of Dr. Diana Deutsch and her discovery we can extract music from spoken words. Here is the link to the wonderful Radiolab story that covers this phenomenon. At the end of our discussion Mark read a quote from Darwin concerning the behavior of fighting cocks to erect their neck feathers - something "Every one must have seen two cocks...preparing to fight with erected neck-hackles. Photo from https://www.behance.net/gallery/4810345/Cockfighting-in-ThailandWe discussed if it was legitimate for Darwin to identify the behaviors he was describing in dogs, cats, horses, monkeys and apes as being fear, affection, joy, anger and astonishment. Mark brought up the idea of Morgan's Canon, which argued against using complex anthropomorphic interpretations of a behavior when a simpler, basal behavioral state can explain the behavior. For example, Tony, Morgan's terrier opened the gate through trial and error and not because of some insight about the gate mechanism.Tony opening the gate so he can go out and sniff some buttsSarah noted that Darwin seemed to ignore the evolutionary history of dogs and cats to help explain their behaviors. Domestic dogs evolved from wolves, a social pack animal, which can explain the complex set of stereotypical dominant and submissive behaviors they exhibit whereas domestic cats evolved from wild cats that were solitary. James declared that Jackals, a group of canines that Darwin incorrectly proposed to be the progenitor of some smaller breeds of dogs, were solitary. Turns out, Jackals are typically found as monogamous pairs, but the social group can increase with young. So they are not solitary like big cats, but they are not as social as wolves.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.

In this episode we discuss the first three chapters of Darwin's On the Expression and Emotion of Man and Animals, and James fails to convince the team to refer to the book as EEMA for short. The first chapters of EEMA lays out Darwin's 3 principle foundations and each of us focused on one of the principles. The three principles are:I. The principle of serviceable associated Habits.—or "I wear my emotions on my sleeve" II. The principle of Antithesis.— or "Turn that frown upside down" III. The principle of actions due to the constitution of the Nervous System, - or "Everyone has a tell"One of the issues we discussed is what Darwin meant by "serviceable" when referring to the physical manifestation of the emotions. It seemed that Darwin felt that the clinched fist when angry or the closing of your eyes when you are startled by a loud noise are adaptive reflexes to prepare or protect you from the perceived threat that would accompany that emotion.We discussed the oddity of Principle 2 in that Darwin seemed to not give adaptive value to the associated behaviors but saw them more as an opposite signal of the emotion associated with Principle 1. One of the clear examples Darwin discussed was the behaviors we see in our dogs and cats when they are expressing anger compared to when they are expressing happiness.Fig. 5. Dog approaching another dog with hostile intentions. By Mr. Riviere.image from http://darwin-online.org.uk/Fig. 6. The Same in a humble and affectionate frame of mind. By Mr. Riviere.image from http://darwin-online.org.uk/James was enamored by the block print of the dog that seemed to be quite friendly with a person's leg. Here is the image.At the end of the podcast we discussed a paper written by Gregory Radick entitled Darwin's Puzzling Expression. Wonderfully the article  is available for free as well as the entire issue ofComptes Rendus BiologiesVolume 333, Issue 2, February 2010, Pages 181-187 which can be found here.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music is Lobo Loco - Spencer Bluegrass 

This is the first episode of the long awaited Season 3 of Discovering Darwin. In this season we will be exploring Charles Darwin's 14th original published book entitled The Expression of the Emotions in Man and Animals. We are reading the 3rd Edition of the book that has been edited by Paul Ekman. Dr. Mark Jackson, Psychology professor at Transylvania University is joining us this season as we tackle this unusual book by Charles Darwin.One of things that makes this book so unusual is that it is considered the first scientific book to utilize photographs. The French neurologist Guillaume-Benjamin-Amand Duchenne had found a man who seemed to lack the ability to feel pain so Duchenne was able to apply electrical probes to stimulate muscle contractions. By carefully stimulating certain muscle groups, Duchenne was able to get his "Old Man" to hold an expression long enough to be captured in a photograph using the early camera system of the times that required long exposure times.  We discussed how Charles began taking notes for this book 33 years earlier when his first child , William Erasmus Darwin, was born. Here is the sweet photograph of a proud father, Charles Darwin, sits with his son William. We discussed the functionality of dressing all young children, regardless of their gender, in dresses.   One of the people that Darwin was reacting to as he wrote his Expression and Emotions of Man and Animals was Charles Bell, a talented artist and anatomist. One of Bell's hypothesis was that emotions are a uniquely human trait that were given to us by our creator and he would show muscle sets that were "unique" to humans for expressing emotions. Darwin, opposed that creation view, and worked to adopt his idea of evolution by descent with modification to explain how emotions, like other traits, in humans when compared to other animals "...do not differ in kind, although immensely in degree." [Descent of Man 1871].James described how beautiful the drawings of Bell were and mentioned the hand on the book illustration as represented below.So what expression do you think this image represents?The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.

In this, the final episode of Season 2, Darwin does some island hoping, takes a surprising return trip to Brazil, and on October 2, 1836, finishes his 4 year 9 month journey. In this episode of the podcast we are joined by Dr. Belinda Sly, a evolutionary developmental biologist and colleague of ours, to discuss Darwin, his thoughts about the voyage, and if it had an effect on Darwin's mental health.The final two chapters of the Voyage of the Beagle are unusual in that Darwin's writing style oscillates between dry technical accounts on how coral atolls are formed, and how different plants, insects, and animals naturally colonize these isolated islands in the middle of the ocean with very melodic and romantic descriptions of the landscapes and peoples he encountered on these far away islands.Atollshttp://geologylearn.blogspot.com/One can imagine how disorienting sailors must have been when they first encountered the unusual geological structure of an island atoll.http://geologylearn.blogspot.com/A ring structure of land that either encompasses a calm marine harbor that may or may not also include an island in the middle, as seen in the Bora Bora atoll above. Darwin proposed that these unique structures came about through two natural process occurring at the same rate. The volcano that rose from the deep ocean floor and erupted to originally form the island would go dormant and begin to erode away.  Once the volcano had cooled, marine corals would begin to colonize the new island in the shallow waters to create the coral reef. Slowly the volcano would subside back into the ocean and concurrently the corals would grow upward and outward at the same rate as the island eroded and sank.http://darwin-online.org.uk/Darwin was the first to actually propose the correct geological model for atoll formation and he spends many pages of Chapter XX explaining his model.Unfortunately Dr. Josh Adkins was unable to join us on the final episode but you can get your Josh fix by listening to his award-winning podcast The CromCast, a podcast dedicated to weird fiction that also has the occasional Bourbons and Barbarians episodes, a series that entertainingly combine bourbon with old school D&D.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music is Remember the Way by Mid Air Machine

"At daylight, Tahiti, an island which must for ever remain classical to the voyager in the South Sea, was in view. At a distance the appearance was not attractive. The luxuriant vegetation of the lower part could not yet be seen, and as the clouds rolled past, the wildest and most precipitous peaks showed themselves towards the centre of the island. As soon as we anchored in Matavai Bay, we were surrounded by canoes. This was our Sunday, but the Monday of Tahiti: if the case had been reversed, we should not have received a single visit; for the injunction not to launch a canoe on the sabbath is rigidly obeyed. After dinner we landed to enjoy all the delights produced by the first impressions of a new country, and that country the charming Tahiti. A crowd of men, women, and children, was collected on the memorable Point Venus, ready to receive us with laughing, merry faces." Chapter XVIII-Voyage of the Beagle After 1.5 year absence, Sarah, Josh and James return to the podcast to finish Voyage of the Beagle. We left Charles out in the Pacific Ocean, sailing the 3,200 miles from the Galapagos to Tahiti. It took the Beagle nearly a month to cover that distance and the sailing was difficult. Tahiti was a welcome sight.A long and brilliantly-white beach is capped by a margin of green vegetation; and the strip, looking either way, rapidly narrows away in the distance, and sinks beneath the horizon. From the mast-head a wide expanse of smooth water can be seen within the ring. These low hollow coral islands bear no proportion to the vast ocean out of which they abruptly rise; and it seems wonderful, that such weak invaders are not overwhelmed, by the all-powerful and never-tiring waves of that great sea, miscalled the Pacific.An Aerial View Of Tahiti...By Sylvain Grandadam Darwin enjoyed the hospitality of the native Tahitians and the rich abundance of fruits, roasted bananas and pineapples, which he admitted tasted better than any pineapple cultivated in a hothouse in England.  While in Tahiti, Darwin embarked on the last of his difficult and challenging hikes when he went with two native Tahitians to hike into the valley of Tia-auru. When I lived in Kauai I hiked around the north shore and I imagine the landscape there is not much different from the Tahitian landscape, both are volcanic islands with Kauai being older (5 million years old) than Tahiti (1.6 million years old).View of a valley in Kauai that looks like Tahitian landscapeIn New Zealand Darwin noted the cultural tradition of the native New Zealanders (Maori) tattooing their lips and areas around their face. We discussed how Darwin recognized the role of fashion in a culture and admitted that his bare un-tattooed face was as unsettling to the Maoris as their inked faces were to him.http://servatius.blogspot.com/2015/10/maori-couple-1880s-with-facial-tattoos.htmlA wonderful description of Maori traditional tattoos can be found here.

This podcast episode is dedicated to Chapter III from Charles Darwin's Origin of Species. The title of the chapter is Struggle for Existence.  We discussed Thomas Malthus and how his ideas of population growth influenced Charles Darwin. In particular, Malthus noted that human population growth is geometric which is clearly represented by the graph below that shows global human population growth in the last 300+ years.  Human population on earth is currently over 7 billion with the estimates that in the next 50 years we may level off somewhere between 7-16 billion people, which is a large margin of error. The thought is that cultural norms and female education will decrease individual female fertility which will ultimately dampen global population growth.If true and human population stabilizes it will be unusual since humans would be exhibiting self-regulation of their population instead of having external mortality factors (disease or predation) determining population size. Graph summarizing human population growth.Although Malthus was correct in his view of human population growth, his prediction about the rate of food availability being linear was wrong because modern agriculture has also shown a geometric increase in yield/acre by utilizing evolution (artificial selection in breeding newer varieties of crops) and fossil fuels to operate machinery, irrigate crops and manufacture fertilizers, pesticides and herbicides to increase crop yield. This phenomenon has been named the Green Revolution and it began in western cultures at the end of World War II. The graphs below show how increases in yield/acre for two food crops (corn and wheat) and two other crops (cotton and tobacco) have mirrored the geometric increase of human population growth. Increase productivity in selected cropsOne of the exciting ideas that Darwin introduces in this chapter is the idea of trophic cascades, the interaction between the various organisms in an ecosystem. We discussed Darwin's beautiful example of the complex indirect relationship between cats in a village and the population of clover in the fields. Recently a complex example has come to light when wolves were reintroduced to Yellowstone national park. The reintroduced wolves altered the foraging behavior of elk thereby reducing the elk negative impact on young tree recruitment which increased forest and understory growth. Increase in tree growth along the river banks stabilized the soil and reduced erosion which resulted in improved water quality and river flow.Ultimately the reintroduction of wolves influenced fish communities, beaver abundance and other indirect effects which are documented in detail in a variety of scientific papers which can be found at the Global Trophic Cascades research program website from Oregon State University. The researchers have linked a large number of their original research papers for free download.From Ripple et al. (2014) Science 343 If you do not feel like reading, then we recommend you watch the short but wonderful TED talk by George Monbiot as he describes some of the complex trophic cascades uncovered in different ecosystems.Josh and Sarah brought up the idea of how invasive species can illustrate the importance of predators and disease in controlling population size since many invasive species can dramatically increase their population size when compared to their native population sizes in the land of origin.We mentioned Josh's favorite study species the Hemlock Wooly adelgid (Adelges tsugae),  kudzu (Pueraria montana var. lobata)  and winter creeper, all of which are invasive in the eastern US. Wooly adelgid image from http://www2.ca.uky.edu/Kudzu image from http://www.forestryimages.orgWinter creeper image from http://www.local12.comURL: http://freemusicarchive.org/music/Kevin_MacLeod/Best_of_2014_1461/Broken_RealityComments: http://freemusicarchive.org/Curator:

"In the morning (17th) we landed on Chatham Island, which, like the others, rises with a tame and rounded outline, broken here and there by scattered hillocks, the remains of former craters. Nothing could be less inviting than the first appearance. A broken field of black basaltic lava, thrown into the most rugged waves, and crossed by great fissures, is everywhere covered by stunted, sunburnt brushwood, which shows little signs of life. The dry and parched surface, being heated by the noonday sun, gave to the air a close and sultry feeling, like that from a stove: we fancied even that the bushes smelt unpleasantly." Chapter XVII - Voyage of the BeagleFrom Darwin and the Beagle, A. Moorehead 1969In this podcast Josh, Sarah and James talk about Darwin's visit to the Galapagos Island and how that experience ultimately contributed to Darwin rejecting the notion of the fixity of species and developing his theory of the evolution and the process to create new species.  The Galapagos islands are a chain of volcanic islands that poke out of the Pacific ocean over 500 miles off the coast of Ecuador.  Although many of the islands are relatively close to each other, Darwin was struck by how the plants, insects, birds and reptiles on each of the islands were distinctly different from the other islands.Bartolome Island, Galapagos Islands, Travel ChannelAlthough most people associate Darwin and his experience with the Galapagos finches in developing his theory of evolution, we make the argument that it was the Galapagos tortoises that first intrigued and befuddled Chuck and stimulated him to begin pondering "...that mystery of mysteries—the first appearance of new beings on this earth."In the Voyage Darwin writes-"I have not as yet noticed by far the most remarkable feature in the natural history of this archipelago; it is, that the different islands to a considerable extent are inhabited by a different set of beings. My attention was first called to this fact by the Vice-Governor, Mr. Lawson, declaring that the tortoises differed from the different islands, and that he could with certainty tell from which island any one was brought. I did not for some time pay sufficient attention to this statement, and I had already partially mingled together the collections from two of the islands. I never dreamed that islands, about fifty or sixty miles apart, and most of them in sight of each other, formed of precisely the same rocks, placed under a quite similar climate, rising to a nearly equal height, would have been differently tenanted; but we shall soon see that this is the case."DARWIN RIDING TORTOISE, HEROES SCULPTURE GARDEN, by MARJAN WOUDAwww.marjanwouda.co.ukJosh talks about Darwin's experiences with these cyclopean creatures, drinking from their bladder and riding them like a horse, and about recent efforts to determine how many different species of tortoises actually exist and the current conservation efforts to protect them.The image of Darwin riding a tortoise reminded us of the old sketch a friend of Darwin's made showing Charles Darwin riding a beetle.Sarah talked about the marine and terrestrial iguanas found on the islands and how Darwin would throw the marine iguana into the ocean for it to rapidly return to shore wherein Darwin picked it back up by the tail to fling it back in the ocean. Darwin repeated this "experiment" until he was convinced that although the marine iguanas were perfectly adapted to swimming in the oceans they preferred to stay on shore, where it was safe.Looking out to sea - https://www.flickr.com/photos/45325473@N04/page2We finished the conversation about the role of the Mockingbirds and Finches found on the Galapagos islands in convincing Darwin that different species of the same type of animal could be found on different islands, although the islands themselves were not remarkably different from each other in habitat and geology. In addition, these islands were not significantly different from volcanic islands of Cape Verde Darwin visited 3.5 years earlier off the coast of Africa, and yet the species found in each of these archipelagos were more closely related to their neighboring continents than they were to each other.Sarah told us about her recent guest appearance on  The Common Descent which is an excellent podcast that discusses the diversity of life, past and present. Check it out!The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music Big Beats Alternative by Sunserarcher http://freemusicarchive.org/music/Sunsearcher/

To celebrate the 186th Anniversary of Charles Darwin setting sail on the HMS Beagle we post a Bonus podcast discussion with Dr. Geoffrey Williams, an economics professor, on the expenses and wealth of Charles Darwin.  Hope you enjoy the conversation!image from Darwin Online

"I climbed up on foot to very near the crest; from the Puna I experienced, I cannot suppose the elevation is less than 8000 to 10000 ft; There was a good deal of snow, which however only remains here in the winter months. The winds in these districts obey very regular laws; every day a fresh breeze blows up the valley & at night, an hour or two after sunset, the air from the cold regions above descends as through a funnel. — This night it blew a gale of wind, & the temperature must have been considerably below the freezing point, for water in a short time became a block of ice. No clothes seemed to oppose any obstacle to the air; I suffered much from the cold, so that I could not sleep, & in the morning rose with my body quite dull & benumbed."  [Voyage of the Beagle, Chapter XVI]In this episode we discuss the various expeditions Charles Darwin organized to explore the Andes mountain range in South America. These adventures are recounted in chapters IX, XII, XV, and XVI in The Voyage of the Beagle.Image from Darwin OnlineWe started our discussion with the Santa Cruz expedition that Darwin and Fitzroy engaged with while the HMS Beagle was grounded for repairs at the mouth of the Santa Cruz river. This 17 day journey occurred from April 18-May 8, 1834 and involved the men dragging three whale-boats upriver hoping to find the source of the river at the base of the Andes mountains. In our discussion James erroneously said the trip was 185 miles but further reading in Fitzroy's account we find the following-"Late on the 4th we returned to our tents, thoroughly tired by a daily succession of hard work, and long walks. At this bivouac we were about one hundred and forty miles, in a straight line, from the estuary of Santa Cruz, or from Weddell Bluff; and about two hundred and forty-five miles distant by the course of the river." [Fitzroy, Narrative pg 356].The men dragged the boats upriver for 14 days until Fitzroy decided it was time to turn back and then it only took them 3 days to return to the HMS Beagle. Sarah discussed the complex geology of the region and the ships artist had come along to make amazing drawings of the scenery. C. Martens. T. Landseer.BASALT GLEN – RIVER SANTA CRUZ.We scanned the wonderful map that Nora Barlow includes in her edited edition of the Diary of the Voyage of the H.M.S. Beagle and have highlighted the 4 different trips we discussed in this podcast.The Santa Cruz journey is indicated by the red line, Andes 1 trip is the pink loop, the Andes 2 expedition is indicated by the green loop over the Andes and the Andes 3 trip is indicated by the purple line.We discussed on our reliance of the wonderful website called About Darwin which maps in detail the various journey Darwin has during the 5 year voyage. Highly recommend the site, great information.Josh discussed the earthquake Darwin experienced and the state of destruction he observed in Concepcion.This reminded James about plate tectonics and how the west coast of South America resides on the suture line between two major tectonic plates - the Nazca and South American Plates.map from https://www.thoughtco.com/map-of-tectonic-plates-and-their-boundaries-1441098As Sarah remarked, Darwin did some amazing geologizing while engaged in those 1,000 mile + expeditions through the Andes and valleys of South America.  He created a beautiful cross sectional map that can be found here- Darwin's map. The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.Interlude music is Little glass men - Moon Shadow

"Whilst going on shore, we pulled alongside a canoe with 6 Fuegians. I never saw more miserable creatures; stunted in their growth, their hideous faces bedaubed with white paint & quite naked.— One full aged woman absolutely so, the rain & spray were dripping from her body; their red skins filthy & greasy, their hair entangled, their voices discordant, their gesticulation violent & without any dignity. Viewing such men, one can hardly make oneself believe that they are fellow creatures placed in the same world. [Beagle Diary, February 25, 1834]In this episode we are joined by our esteemed colleague Dr. Jeremy Paden to discuss Darwin, Fitzroy, and other early explorers views of the native peoples of Tierra del Fuego.  As we outlined in episode 1 of this season, Fitzroy had kidnapped four native Tierra del Fuegians with the hopes of converting them to Christianity and ultimately returning them back to their native lands to nucleate the conversion of the "savages" to a live a civilized agrarian life of tubers, legumes, and bible verses.Unfortunately, Boat Memory, one of the natives that Fitzroy had gang pressed into missionary service died from small pox in England but the other three - "Fuegia Basket", "Jemmy Button", and "York Minister" survived their journey to England,  their education therein, and their ultimate return to tip of South America to rejoin their family and friends.Sketches by Fitzroy of his kidnapped victims. Image from Darwin Online.On January 23rd, 1833 the HMS Beagle stopped by Wollya bay (later spelled Woolliah and then Wulaia] to build a outpost for Jemmy, Fuegia and York. Fitzroy and his crew, along with the help of Mr. Matthews, a missionary Englishman, planted crops, built a cabin, and transferred the useless accouterments of "civilization".In Keith Thomson’s book HMS Beagle: The story of Darwin’s Ship he vividly describes the scene and foreshadows the failure of the settlement:“Over the next week the party from the Beagle built a small outpost and finally unloaded all the incredible paraphernalia that had been sent from England by well-wishers, all the Victorian knickknackery that seemed so splendid in London but appeared ridiculously out of place at this remotest end of the world. A seemingly unending pile of soup tureens, chamber pots, wineglasses, and beaver hats was transferred from the boats, while more practical souls set about planting potatoes, beans, root vegetables, lettuce, and cabbage in the gardens”. [pg. 172][Correction] During our retelling the story of the return of the three Fuegians we mixed up the time scale of events. We stated that Mr. Matthwes survived a year at the outpost before he was picked up by Fitzroy but in actuality he only lasted about 2 weeks before he abandoned the missionary effort and left the HMS Beagle to join his brother in New Zealand. At then end of the podcast we enjoyed a lively discussion on how negatively did Darwin view the natives of Tierra del Fuego?The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh. Interlude song - Missionary Man by the Eurythmics

In this episode we discuss the interesting extinct and extant mammals that Darwin collected in South America during his voyage on the Beagle. James makes an argument that it was the mammals that Darwin collected that stimulated his idea that species evolve. Sarah talks about why there are so many large mammals in Africa and not in South America, which Darwin thought was odd since vegetation growth is much more dense and thick in the rain forest of South America compared to the plains of Africa.Some of Darwin's unique species he collected on his voyage.From Darwin's journal where he realizes species transmutate"In July opened first note book on 'transmutation of Species'—Had been greatly struck from about month of previous March on character of S. American fossils—& species on Galapagos Archipelago. These facts origin (especially latter) of all my views."  From Darwin's Journal July 1837.Darwin was struck by two interesting aspects of the mammals of South America. The first was that there was a strong correspondence between the mammals that he shot, collected and ate in South America with the fossils he collected in the same area. Three major kinds of mammals intrigued Darwin during his exploration of South America. The first is the sloths,  a slow moving herbivore mammal that are adapted to feeding on leaves and fresh buds of the cecropia tree. The first mammal Darwin collected was giant bones from the megatherium, an extinct species of giant ground sloth.https://media.mnn.com/assets/images/2017/01/Sloth-Hanging-Tree-Branchhttp://www.prehistoric-wildlife.com/species/m/megatherium.htmlhttps://commons.wikimedia.org/wiki/File%3AMegatherium_americanum.jpgThe other mammal type that intrigued Darwin was the fossil giant Glyptodont which looks similar to the extant armadillo still found in from South America up through Central America into the southern regions of North America.http://media.npr.org/http://www.prehistoric-wildlife.com/index.htmlThe other two interesting mammals Darwin collected as fossils was the Toxodon and the Macrauchenia. Here are some reconstructions of the animals by talented and imaginative artists.http://prehistoricpark.wikia.com/wiki/ToxodonFollow this link to a wonderful National Geographic article that discusses some of these amazing prehistoric mammals. http://darwin-online.org.uk/graphics/Zoology_Illustrations.htmlDuring the discussion Sarah mentioned the diversity of form prehistoric mammals exhibited in the fossil record. The image below collects some of the various forms of elephants that have evolved over the past 65 million years. Note how diverse the tusks, modified teeth, have developed in the various species. https://www.natgeocreative.com/comp/05/682/457127.jpgJosh mentioned how impressive it is to watch vampire bats feed. Here is a link to cool video from National Geographic that shows interesting bat behavior but the narrator tries to hard to be cute.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh. Interlude music is Suede Head by Red Star Martyrs

In this episode of we are joined by the historian Dr. Gregg Bocketti (Transylvania University) in a discussion on the cultural and political conditions of South America when Charles Darwin set shore in Brazil and surrounding territories in the 1830's.In 1831, a year before Darwin was to arrive in Rio de Janerio, the emperor Don Pedro I decided to return to Portugal  to help his daughter reclaim the throne of Portugal and left behind his 5 year old son Don Pedro II to be regent of the Kingdom of Brazil.  Because of his weak regency and lacking of ruling control, local strongmen rose in power and resolved their disputes through local civil wars.Pedro II at around 11 years of age. WikipediaGregg vividly described the diverse social and cultural life Darwin would have encountered in in Rio de Janerio. At the time that Darwin visited Brazil it was still a country based upon a slave economy, which is clearly evident in the painting below that was created around the time Darwin was visiting the city.John Steinmann, a Swiss artist, lived in Rio de Janeiro between 1825 and 1833.Gregg spoke about the horrific conditions that the slaves had to endure and the various roles slaves played in the Brazilian economy. One of the interesting aspects of slavery in Brazil was that some slaves took on trades and technical trade positions and were able to work on the side to make extra money for themselves which could be used to purchase their freedom.Painting by French painter Jean-Baptiste DebretFollow this link to a story on NPR that gives a vivid account of slavery in Brazil and how they were one of the last countries in the Americas to abolish slavery.http://www.npr.org/sections/parallels/2013/11/12/244563532/photos-reveal-harsh-detail-of-brazils-history-with-slaveryDarwin spent a time exploring the countryside of Brazil, Argentina and Chile and on some of those expeditions he would be guided by the local cowboys known as gauchos. Darwin was impressed with the gauchos riding ability and skill in capturing animals with the bolas, a set of heavy balls affixed to the end of ropes and twirled and thrown to entangle the legs of rheas, guanacos or any other small prey they were hunting.

In this episode we discuss the extensive library on the HMS Beagle that was created by Charles Darwin and Robert Fitzroy.  Over 400 books were in the ship's library and the catalog had a heavy emphasis on travel accounts (travelogues), natural history and geology.  We discussed Humboldt and his influence on Darwin and Jeremy told the story about the dragon tree and Darwin's wish to travel the lands of Humboldt to see the same sights as Humboldt.Dragon trees in the canary islands (picture from http://pixdaus.com/canary-islands-dragon-tree-or-drago-tree/items/view/267293/)Here is Humboldt's description of the dragon tree-Although we were acquainted, from the narratives of so many travellers, with the dragon-tree of the garden of Mr. Franqui, we were not the less struck with it's enormous magnitude. We were told, that the trunk of this tree, which is mentioned in several very ancient documents as marking the boundaries of a field, was as gigantic in the fifteenth century, as it is at the present moment. It's height appeared to us to be about 50 or 60 feet; it's circumference near the roots is 45 feet. We could not measure higher, but Sir George Staunton found, that, 10 feet from the ground, the diameter of the trunk is still 12 English feet; which corresponds perfectly with the assertion of Borda, who found it's mean circumference 33 feet 8 inches, French measure. The trunk is divided into a great number of branches, which rise in the form of a candelabrum, and are terminated by tufts of leaves, like the yucca which adorns the valley of Mexico. It is this division, which gives it a very different appearance from that of the palm-tree*. [Humboldt, Alexander von. 1814-1829. Personal narrative of travels to the equinoctial regions of the New Continent, during the years 1799-1804. pgs 144-145]Since 36% of the books in the Beagle library were travelogues, and Darwin's own Voyage of the Beagle is a travelogue, we invited Dr. Jeremy Paden, professor of Spanish Literature at Transylvania University, to discuss with us the role of travelogues in the 16th-19th century as a literature form.During our discussion Jeremy highlighted Thomas Falkner as an influential travelogue writer who wrote  A description of Patagonia, and the adjoining parts of South America (1774).  Falkner described the region of Patagonia, a rugged area at the tip of of South America that also encompassed the Streights of Magellan.Straits of MagellanUnlike the map above which show the Straits of Magellan as a simple channel, the real Straits of Magellan are quite complex and convoluted as seen in the Google map below. Notice the large number of cul-de-sac inlets and waterways that can easy lead you astray.We noted that the tip of South America looks more like a spongiform brain that has mad cow disease as shown in the image below, left image is a brain with Creutzfeldt-Jakob disease and brain on the right is normal brain.James highlighted an unusual book in the collection - Werner's Colours, a small book that includes colour swatches that Darwin used as reference when he was taking notes of specimens.Excerpt from Werner's ColoursYou can peruse the entire Beagle library at the Darwin Online website.At the end of the podcast we spoke with Dr. Paden about his own research and interest in poetry. James mentioned his appreciation of Jeremy's poem on the liver fluke parasite and we reprint it here-CompulsionFalling from the masticating jaws of ungulatesthat clip the tips of grass blades, the black antescapes this evening’s immolationand the circuitous route of cud-balls,from stomach to teeth, stomach to teeth.Ignorant of why it leaves the sweet feastof slime balls secreted by common land snails,come dusk, the ant climbs again the broad greenleaf to spend the night in sirshasana​,​pinschers clamped ​to the end of a grass blade.Larval lancet liver flukes, encystedin snail-trail droppings, once eaten,​ move to​the ganglion below the gullet,​ and force ​​Formica fusca to climb​ the blade​ andwait for the grazing cattle to come home.If you are interested in reading more of Jeremy Paden's poems you can find his published book of poems concerning mining in Chile here or here.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh. Interlude music was Procreation by Little Glass Men

In this episode Sarah, Josh and James discuss the opening chapters of Voyage of the Beagle where Darwin recounts the initial months of his voyage that includes an aborted stop at the Canary Islands, a visit to Cape Verde and then his first overland trip in Brazil. James discussed how Darwin spent as much time off the Beagle traveling overland than he did sailing in the Beagle.By Jules de Caudin - Relation complète du naufrage de la frégate La Méduse faisant partie de l'expédition du Sénégal en 1816, by A. Correard, H. Savigny, D'Anglas de Praviel and Paul C.L. Alexandre Rand des Adrets (dit Sander Rang). Reprint 1968 by Jean de Bonnot éditeur., Public Domain, https://commons.wikimedia.org/w/index.php?curid=19330900James talked about the work of the scholar John van Wyhe who scoured through Darwin and Fitzroy’s diaries and journals to reconstruct the day-to-day itinerary for the HMS Beagle during the 5 year voyage and lists location, latitude/longitude coordinates and where Darwin was located – either on ship or on land. When you break down of the 1,740 day voyage you realize Darwin made great efforts to spend time away from the ship. From Darwin’s perspective he almost equally split his time between being at sea, at anchor or traveling on land. Based on the itinerary of the Beagle Darwin spent 580 days at Sea, 566 days at anchor and 594 days away from the Beagle on overland excursions. Interesting, even when anchored or exploring on land, Darwin would return to sleep on the Beagle which he found to be very comforting.  Darwin spent 1,144 nights on the beagle (65.8% of the trip) whereas he spent 596 nights off ship which is only 34.2% of the trip. Over half (55%) of that time was spent in South America alone. James discussed how Darwin's diary and notebooks in the first 2 months of the journey included interesting details that were absent in the Voyage. In particular, Josh talked about the ritualized hazing that sailors would inflict on the new crew members when they crossed the equator, a ritual called the line-crossing ceremony.Josh referenced this nice article from the Atlas Obscura website that discusses the odd ritual of hazing as one crosses an imaginary line on the earth's surface. Sarah also talked about the Tropic of Cancer and the Tropic of Capricorn and how the wind patterns associated with those imaginary lines on the earth drove trans-Atlantic slave trade and the conquest of the New World.We focused on the first overland trip that Darwin took when he landed in Brazil. This was the first of many trips that Darwin took while Captain Fitzroy fastidiously checked his charts and maps by reiterately sailing up and down the coast of South America.http://www.mun.ca/biology/scarr/Voyage_of_the_Beagle.jpgAs Darwin traveled overland he mentioed many interesting animals and plants he encountered in the jungles of Brazil. One group of animals Darwin became enamored with was planaria (Plathyhelminthes). Interesting, even to this day new species of flatworms are being discovered in Brazil.James pointed out that this group of animals also exhibit great species diversity in the marine habitat where they show a beautiful diversity in colors. Here are just few examples of the amazing color diversity of marine flatworms one can find with a simple google image search.Sarah became obsessed, like Darwin, with bioluminescence. Sarah discussed the amazing evolution of bioluminescence and how it has evolved independently across a number of disparate phyla and kingdoms. Darwin was particularly enamored by a large click beetle that incorporates bioluminescence in mating display. One of our students took a wonderful picture of the same beetle during our Tropical Ecology class to Belize.photo by Kali MattinglyThe opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh. Interlude music http://freemusicarchive.org/music/DubRaJah/Reprise/7_Chitwan

 This is the first episode for Season 2 of Discovering Darwin. We have titled this season Darwin the Adventurer because we plan to explore in detail the Voyage of the Beagle, Darwin's five year around-the-world survey in which he collected the specimens and made the observations that ultimately led him to develop his theory of evolution and write On the Origin of Species.In this episode we introduce the three major characters involved in the famous voyage- Captain Robert Fitzroy, Charles Darwin and the ship the HMS Beagle. HMS Beagle in the Galapagos (painted by John Chancellor)Josh introduced us to Pringle Stokes, the original captain of the Beagle during its maiden voyage (1826-1830) to South America on a survey voyage to map the Straits of Magellan at the tip of South America. However the HSM Beagle, a Cherokee class brig-sloop which were often derogatorily referred to as "coffin brigs", was a difficult ship to control in the severe winds, strong currents, high seas, and rogue icebergs that were typically encountered around Cape Horn. Josh explained how Pringle Stokes commits suicide on the ship in 1828 and Robert Fitzroy is assigned to captain the ship after Stokes demise. Robert Fitzroy - photo by Hemus, Charles 1849?-1925 [Public domain], via Wikimedia CommonsWe talked about the contingencies of history and how some tierra del fuegian children became the nexus for Fitzroy, Darwin and the HMS Beagle.  We will dedicate a later episode to the depressing tale of Jemmy Buttons, York Minister and Fuegia Basket, kidnapped tierra del fuegians who rejected their roles as Christian missionaries for England and forever haunted Robert Fitzroy and many others back in England.Drawings by Robert FitzroyBecause of Robert Fitzroy's short temper and willingness to lash out to those crew members he felt were wanting he was given the nickname "Hot Coffee" by the crew.  A meticulous man and data collector, Fitzroy would often retrace his sailing path to confirm his charts and maps, a level of meticulousness that would exasperate his crew and Darwin.Fitzroy's iterative approach to sailing. Map from https://www.britannica.com/topic/Beagle-shipAdd captionThe opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh. Interlude music is Rite of Passage by Kevin MacLeod

In this episode we discussed Chapter XV - Recapitulation & Conclusion from Darwin's Origin of Species. It is our final podcast of this season and we chose not to recapitulate as much as discuss how Darwin's book was received at the time and how Darwin handled the release of his book.Although only 1250 copies of Origin of Species was published in the first edition, Darwin purchased 80 or so copies himself and Mudie's Circulating Library purchased 500 copies for use in their subscription service library, a service widely used by many middle class British folk. It was through the subscription library that allowed Darwin's ideas to be widely distributed to the general public while fevered debates occurred in churches and academic halls.The original 1859 publisher of Origin of Species was the Murray Publishing House book and the publisher was very generous in allowing Darwin to make corrections after the first printing run which is why the 2nd edition of OoS has a 1860 publication date.We discussed how Darwin was often portrayed as an ape in cartoons published at the time. When we discussed the infamous images of monkey-like Darwin James erroneously associated those images with the famous Punch magazine but it turns out the ones he was thinking of came from other magazines of the time.Charles Darwin considering the fashion of the time - the bustle (Fun magazine 1872) from The Hornet magazine, 1871We really appreciate you listening to our podcast and we hope you return later this fall when we return with Season Two - Darwin the Adventurer.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh. Interlude music is bensound retro soul

This episode discusses Chapter XIV where Darwin applies his ideas of evolution and descent with modification to explain the developing "natural system" of classification, the unity of embryos and why organisms have rudimentary or vestigial organs.  Classification From the most remote period in the history of the world organic beings have been found to resemble each other in descending degrees, so that they can be classed in groups under groups. This classification is not arbitrary like the grouping of the stars in constellations. The existence of groups would have been of simple significance, if one group had been exclusively fitted to inhabit the land, and another the water; one to feed on flesh, another on vegetable matter, and so on; but the case is widely different, for it is notorious how commonly members of even the same sub-group have different habits.Cuvier in 1817 proposed a system of classification that recognized animals as belonging to one of four forms  - Vertebrata, Mollusca, Articulata (arthropods) and radially shaped animals (Radiata). image from http://www.buffalolib.org/content/milestones-science/georges-cuvierDarwin argues that the hierarchical system of classification mirrors his idea that new species formation mirrors the pattern of inheritance and genealogy we see in family tree.   A nice example is the phylogeny of placental mammals, those are mammals different from marsupial mammals (kangaroos, opossums, etc.) and monotremes (egg laying mammals like platypus)  in that they retain the embryo internally in a placental sac where they feed and protect the developing embryo. Placental mammals represent the majority of extant species of mammals today and seem to have evolved from three major geographical locations - Africa, Laurasia and South America. This is a a beautiful artistic representation of the placental mammal phylogenetic tree.http://eurwentala.deviantart.com/art/Eutheria-345487389A comparison of early development of placental mammals from the Afrotheria clade (left most branch) shows similarities and divergences in the different types of mammals. [A.. Tenrec [tenrecoidea], B. Golden mole [Chrysochloridae] C. Elephant shrew [Macroscelididae] D. aardvark [Tubulidentata] E. Bush elephant [Proboscidae] F. dugong [Sirenia] G. hyrax [Hyracoidea] Image from Hautier, Lionel, et al. "Patterns of ossification in southern versus northern placental mammals." Evolution 67.7 (2013): 1994-2010.Modern phylogeny and classification is based on Darwin's ideas of descent with modification and we now use DNA, RNA, and protein sequences to expand and improve our understanding of the relatedness of organismsEmbryology We have seen that the members of the same class, independently of their habits of life, resemble each other in the general plan of their organisation. This resemblance is often expressed by the term "unity of type;" or by saying that the several parts and organs in the different species of the class are homologous. The whole subject is included under the general term of Morphology. This is one of the most interesting departments of natural history, and may almost be said to be its very soul. What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include similar bones, in the same relative positions? Homologous bone structure of tetrapod limbsJames attempted to differentiate homologous structures from analogous structures but showed how complicated it can be when discussing flying adaptations in mammals. As you can see in the figure above, the limbs of birds, bats, humans, seals and turtles contain the same bones in the same configuration making them homologous in morphology. What changes in the relative size to each other not their relative position. In vertebrates, the evolution of powered flight occurred independently three times - in Pterosaurs (reptiles), bats (mammals), and birds (again reptiles) so their wings are functionally analogoussince they are wings constructed of different specific materials. James erroneously said that the pterodactyl wing was from a super elongated index finger but in fact it is the 4th digit what we associate with the pinky finger.  We colored the figure below of a pterodactyl wing to conform to the color legend in the figure above. Embryology Earnst Haeckel was a famous scientist in Darwin's time who applied Darwin's idea of the evolution of organisms in his studies of the embryonic stages of chordatesAs Sarah mentioned this set of illustrations were updated but the overall conclusion does not differ. Follow this link to read a wonderful summary of the Haeckel embryo controversy with modern drawings and interpretation. Overall embryo development does show that chordates exhibit very similar and distinct stages of development whereas the adult forms can be quite different in form.Rudimentary Organs Humans exhibit a number of traits, that we see in other mammals, but are degraded or rudimentary in their form. Some classic examples we discussed were the coccyx (tail bone), wisdom teeth and appendix but failed to mention the degrading nictating membrane in the corner of our eyes. In other chordates it is semitransparent film that can over the eye to clean and protect it. Ours is reduced to a little nubbin in the corner of our eye.http://www.bio.miami.edu/dana/pix/nictitans.jpgThe opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY interlude music is Otrov by Black Bear Combo http://freemusicarchive.org/music/Black_Bear_Combo/

In this episode we gather our liquid strength and courage to work our way through two chapters of Origin of Species, Chapter XII - Geographical Distribution and Chapter XIII - Geographical Distribution continued.  Although Sarah predicted the podcast would last 3 hours we luckily were able to restrain ourselves to 1 hour and 28 minutes.We do have two corrections to make-#1  Although Josh declared that Noah's Ark came to rest on the top of Mt. Sinai the general view is that it actually settled on Mt. Ararat.#2 James mentioned the relationship between flightless birds (ratites) and the breakup of paleocontinent of Pangea when he should have said Gondwanaland instead.Chapter XII-XII These two chapters have been present in OoS since the first edition and it is in these chapters that Darwin defends his model against the prevailing view of the time - special creation. To make his argument Darwin uses modern distribution patterns of plants and animals on continents and islands, the success of introduced species to new habitats, experiments he conducted at Down House and data he collected from citizen scientists. Geographical Distribution  There is hardly a climate or condition in the Old World which cannot be paralleled in the New—at least as closely as the same species generally require....Notwithstanding this general parallelism in the conditions of the Old and New Worlds, how widely different are their living productions!Sarah discussed the idea of the monkeys from Africa (Old World Monkeys) are quite different from the monkeys found in South America (New World). In Madagascar are found the prosimians "almost monkeys" like lemurs, aye-aye, and sifakas.By Joseph Meyer - MKL online at Retro Bibliothek, work 149, 2009, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2598452On the continent of Africa are a large diversity of primates that range from leaf-eating species like the colobus monkeys to the generalist species like the vervet monkeys and baboons.  In addition gorillas and chimps which are tail-less apes are also in Africa (we realize that these are not monkeys but they needed to be mentioned none-the-less).www.discovery.comThe New World monkeys are quite different in form, long limbed with many species having a prehensile tail which they can use as a 5th limb.http://www.wildernessclassroom.com/students/archives/2005/03/spider-monkey.htmlJosh talked about the rich diversity of marsupial mammals found in Australia, the most striking is(was) the Tasmanian Wolf, a marsupial carnivore that looks like a dog but it is more closely related to a kangeroo! Here is a haunting silent 1936 film of the last known living Tasmanian wolf filmed in captivity. James discussed Darwin's interest in the flightless birds like the ostrich, cassowary, rhea, emu, tinamou and kiwi and Josh reminded us of the extinct Moa. This picture shows the relative sizes of the kiwi, ostrich and moa with the eggs. Notice how large the egg of the Kiwi is relative to its body size. It is the largest egg per body size while the ostrich egg is one of the smallest relative to the body size!Until recently the prevailing view of flightless bird evolution was that the early flightless bird evolved before the continent of Gondwana broke up into the separate continents and then each lineage of flightless bird evolved on their prospective continents - Rheas in South America, ostrich in Africa, Emu in Australia and Kiwi and Cassowary in New Zealand. Recent molecular evidence has challenged that view and actually argues that "flightlessness" evolved independently three times.We discussed the various experiments Darwin conducted with seed dispersal in salt water or in the guts of birds and fish as well as insects and seeds being dispersed on the feet of duck, swans and other semi-aquatic birds. James was reminded of a childhood story in a Dr. Dolittle book, Doctor Dolittle's Garden in which a beetle recounts being brought to England on the foot of a duck.http://gutenberg.net.au/ebooks06/0603431h.html#d5_THE_WATER_BEETLESarah brought up the idea of endemics, and how unique species with limited geographic distributions are often found on islands or high elevation habitats which supports Darwin's model of isolation and speciation. Sarah used the Silversword as an example, a beautiful plant that is found only on the high elevations of Halaekala on the island of Maui in Hawaii. James exposed the beauty and elegance of the plant so here is a picture he took last May 2015.Flowering silversword - photo by James WagnerThe opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY interlude music Octopussy by Juanitos. http://freemusicarchive.org/music/Juanitos/

Let us now see whether the several facts and laws relating to the geological succession of organic beings accord best with the common view of the immutability of species, or with that of their slow and gradual modification, through variation and natural selection.In this episode we explore Chapter XI that deals with the fossil record and how patterns in the fossil record fit with Darwin's model of descent with modification. We begin the discussion with Darwin's views on extinction and how this phenomenon is part of his model of evolution. Sarah introduced the idea that extinction occurs at two different rates - normal background rate of extinction where species themselves have a measured lifespan based on how long they exist in the fossil record. Current analysis of the fossil record indicates that many species persist for a period of time and then go extinct. From this  data scientists calculate an average lifespan for a species - That is, how long in the geological record does a species typically persist? Many authors have written about this idea and many of their findings have been summarized in Extinction Rates, a book edited by J. Lawton, and R. May (1995).Generally species lifespans are varied and biased by the size of the organisms. Small unicellular marine dinoflagellates have species "lifespans" in the 10's million years whereas large multicellular Cenozoic animals had a species 'lifespan" of 1-2 million years. These normal background rates of extinctions in the fossil record are punctuated by five massive extinction events where 75%-96% of all species went extinct. Sarah mentioned the dramatic "soot' line that demarcated the mass extinction event called the K-Pg (formally called the K-T) extinction event that occurred 66 million years ago. This extinction event was correlated with a thin layer of metal iridium that is visually and chemically distinct from rock material layers above and below the line. This layer was now thought to be have been created when a small asteroid impacted the earth near the Yucatan peninsula contributing to massive habitat destruction and climate change. These massive changes in climate are thought to have contributed to the extinction of all non-avian dinosaurs.image from http://waynesword.palomar.edu/images2/KT1c.jpgSarah recommended a book on extinctions by Peter Ward called Under a Green Sky: Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us About Our Future (Harper 2008). Affinities of past to current organismsLet us now look to the mutual affinities of extinct and living species. All fall into a few grand classes; and this fact is at once explained on the principle of descent.We discussed how many of the organisms in the fossil record can be directly related to species we see today - the wide array of extinct elephants themselves are a dramatic example of extinct forms being related to extant forms today.image from http://img13.deviantart.net/1309/i/2015/120/9/7/elephants_by_fotostomias-d34pdf2.jpgJames spent some time explaining the background story of the archeopteryx fossil that was found in 1861 in Germany just after Darwin published Origin of Species. Photograph: Jason Edwards/Getty Images On the photo above notice the fingers on the wing and the long bony tail that extends off of the pelvis region. Museums are now creating displays that highlight the feathered dinosaurs that have been found in the past 10 years.  In 2016 the American Museum of Natural History opened a display that highlighted many new feathered dinosaurs.http://www.nytimes.com/2016/03/18/arts/design/fine-feathered-fiends-dinosaurs-among-us-at-the-american-museum-of-natural-history.html The relationship between organisms we see today to extinct versions in the fossil record is one of the stronger pieces of evidence that supports Darwin's model of descent with modification. In the next episode we will discuss how this relationship between extinct and extant organisms is actually restricted geographically, that is the mammals in the fossil record of South America are similar to the mammals you find in South America today, whereas they are different from those mammals you find, either in the fossil record or living, in Europe, Africa, Australia or Asia. Ontongeny Recapitulates PhylogenyJosh introduced the idea that embryos of organisms can reveal their evolutionary past since they often exhibit structures during development that are more fitting to earlier evolutionary forms. It was formally developed by the famous biologist Ernst Haeckel (1834-1919) in which he argued that organisms have developmental stages that represent earlier stages of their evolutionary heritage. By Romanes, G. J. - Romanes, G. J. (1892). Darwin and After Darwin. Open Court, Chicago., Public Domain, https://commons.wikimedia.org/w/index.php?curid=823180Although the drawing above has been discredited because Haeckel was said to have taken liberties in scale and overly emphasizing some structures, it is clear that early embryonic stages of many chordates exhibit clear gill arches and a well developed tail that becomes greatly reduced or lost during development. Josh queried us about what type of tail we would most prefer - foxy tail was by the far the best choice. interlude music ishttp://freemusicarchive.org/music/Latch_Swing/demo_2008/Rythme_Gitan

...so must the number of intermediate varieties, which have formerly existed, be truly enormous. Why then is not every geological formation and every stratum full of such intermediate links? Geology assuredly does not reveal any such finely-graduated organic chain; and this, perhaps, is the most obvious and serious objection which can be urged against the theory. The explanation lies, as I believe, in the extreme imperfection of the geological record.  [406] This episode focused on Darwin discussing the state of the fossil record, why he felt transitions may be rare and why he does not think the imperfection in the geological record was fatal to his theory. We discussed three of his major issues with the fossil record and then discussed the age of the earth and the sudden appearance of diversity in the fossil record. A phenomenon often referred to as the Cambrian Explosion.How to make a fossil? One of the challenges of creating a fossil is avoiding the rapid decay and destruction of the organic material by bacteria, fungi and other decomposers.  The majority of the decomposers require oxygen to live so a successful fossilization event requires the remains to settle in an area that is anaerobic (anoxic for aquatic systems) (without oxygen). Anaerobic conditions occur in deeper waters where oxygen is slow to replenish from the surface, or it can occur in wet terrestrial systems like bogs or river banks where wet saturated soils can become anaerobic. We didn't mention in the podcast the amazingly preserved 1,000-2,000 year old humans discovered in peat bogs in Europe. These acidic and anoxic environments deter the growth of most bacteria and fungi.image from: http://ngm.nationalgeographic.com/2007/09/bog-bodies/clark-photographyThis is a picture of a sheep that fell into a ditch that was then frozen over, although it is not technically a bog, it does show the difference between access and lack of access of decomposers to a body.image from: https://i.imgur.com/S6Hn8i6.jpgUltimately the conditions that favor fossilization result in a bias in who gets fossilized which greatly biases and restricts the fossil record. In general you can say that to become a fossil you should be:Small and abundant. The more abundant you are in the environment the more likely you could experience the rare opportunity to become fossilized. Live in or near an aquatic environment.Have hard body parts than can resist decay. Scales, shells, bones, exoskeletons and woody material often resist decay whereas flesh, hair and soft tissue not so much.If you are small, blind, sessile and attached to the sea floor you are more likely to become a fossil or fossil imprint than if you are large, active and run across the Serengeti or swim in the shallow, wave disturbed seas.Although the fossil record is biased towards small, aquatic organisms there are museums full of large and dramatic fossils that contradict the rules above. So when you consider the improbability of a creature becoming a fossil the fossil record is actually quite impressive!photo of Sue by James WagnerIs evolution predictable?James mentioned that evolution tinkered with different materials or metabolic pathways but ultimately settled on a few systems that are widely utilized across the diversity of life. In particular we discussed how evolution utilized many different chemical mixtures to create a hard support system (endoskeletal, shell, or exoskeleton) with an interesting alternative seen today in the "glass" sponges. Glass sponges utilize silica to create their hard spicules, the support material utilized by sponges to give strength and support to the jumbled array of barely specialized cells that constitute a sponge. Unlike most sponges which create individual spicules which they assemble with the organization that resembles a game of pick up sticks, spicules by http://www.jeolusa.com/Portals/2/ModuleDNNGridGallery/ncaor_india_sponge-spicules.jpgthe glass sponge silica spicules fuse into a large basket-like structure that remains intact after the sponge dies. http://oceanexplorer.noaa.gov/explorations/03edge/logs/aug23/media/glass_sponge.htmlWe discussed the crazy idea that early evolution experienced a fork in the road when it came to building a mineral based hard skeleton - it could have used silica as the material or calcium carbonate/phosphate. Josh mentioned the downside if we had evolved a glass skeleton.http://www.glasskulls.com/clear-skull/We also discussed the other major evolutionary fork in the road - green versus purple photosynthetic systems. Here is a beautiful picture showing a mat of purple photosynthetic sulfur bacteria floating among a pad of green algae.https://sites.google.com/site/botany317/session-2/bacteria/green-purple-bacteriaIf we rewound the tape and replayed evolution could we have ended up in a purple world with fragile glass skeletons?The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY Copyright: Attribution-NonCommercial-ShareAlike: http://creativecommons.org/licenses/by-nc-sa/3.0/   Interlude music is Little Lilly Swing by Tri-Tachyon which is licensed under a Attribution License.

We dedicate this episode of the podcast to Chapter 9 - Hybridism in Darwin's Origin of Species (OoS). We all agree that this chapter is one of the most challenging chapters to read in OoS. In this chapter Darwin force marches the reader through example after example of hybrids while simultaneously admitting his ignorance on why these creatures should exist.It is not inherently obvious to the reader why they are being subjected to this catalog of biological anomaly and minutiae concerning pollination of orchids and other flowers but Darwin is adamant to share his knowledge, like a proud new parent inflicting others to look at numerous photos of their newborn. Darwin , early in Chapter I of OoS, argued against the notion that new species are formed through hybridization of existing species and we expected him to make that point in this chapter, but he never really does.It seems that by the end of the chapter we are exhausted from Darwin's recounting various animal and plant hybrids and admitting his ignorance of sterility in hybrids but that does not dissuade Darwin from concluding he was right all along - “…the facts given in this chapter do not seem to me opposed to the belief that species aboriginally [emphasis added] existed as varieties”. Darwin stays on point.We started off our discussion identifying our favorite hybrids. Josh first suggested mermaids as his favorite hybrid but James required he offer up a "real" hybrid.Mermaids James grew up with in FloridaJosh introduced us to the Liger, a hybrid between a male lion and female tiger both species have 38 chromosomes which also allows for reciprocal mating. Male tigers and female lions create tigons. The hybrid nomenclature is a portmanteau word derived from using the male species as the prefix and the female as the ending of the name hence a liger and tigon being separate types of hybrids.900 lb Hercules Sarah mentioned the Zedonk, a hybrid between a zebra and a donkey. This is another one of the hybrids that are created artificially in captivity. Few people realize that there are actually three different species of zebras - Grevy's, Plains and Mountain zebras - and each species has their own number of chromosomes. Grevy's zebras zebras have 46 chromosomes, Plains zebras have 44 and the Mountain zebra has 32 chromosomes whereas the donkey has 62.Image from Carole Coleman James suggested the Grolar, a hybrid between a grizzly and polar bear, was his favorite hybrid.A grizzly bear with her grolar cubsUnlike the liger and zedonk, the grolar occur in nature when the two species of bears interact. Historically grolar bears were less common since Grizzly bear distribution was further south than Polar bears but the warming of the climate has caused both bears to extend their range, polar bears southward and grolar bears northward, such they now more commonly overlap during the breeding season. Research suggests Polar bears "recently" diverged from brown bear ancestors with the speciation event occurring only 343,000-479,000 years ago. A mere blink of time in terms of the geological record.We discussed the most famous of all hybrids, the mule and how it is formed from the male donkey breeding with a female horse. Pictured below is a horse (left) and a mule (right) showing how the mule is often much larger than either of its parents, an example of Hybrid Vigor. picture by MerleWe noted that the mule hybrid can only be formed from male donkeys and female horses and rarely rarely formed from a male horse and female donkey. Sarah suggested that the reason the mule can only be formed from a male donkey and female horse has to do with the constraints of difference in gestation times between horses and donkeys. It turns out that horse gestation is 11-12 months whereas donkey gestation period is 11-14 months. There is a lot of overlap in gestation time between the two animals but it is an intriguing idea to consider it may influence non-reciprocal successful mating.  We introduced the idea of prezygotic isolating mechanisms and how they would evolve to prevent hybrids from being formed. Behavioral isolation is frequently seen in the complex displays and calls given by a variety of birds species and James mentioned the beautiful flashing patterns exhibited by the different species of fireflies. The image below shows the species-specific color and flash pattern of lightning bugs in Florida.Go here to learn more about firefliesJosh introduced us to the sordid and dark world of duck mating behavior and male duck genital morphology. Here is just one example of the size and complexity of the male duck penis which has evolved in response to female duck vaginas. Female ducks have evolved elaborate shaped vaginas to avoid fertilization from other species of ducks.This interesting topic is covered nicely in this short article here. Sarah spent some time explaining the intricacies of pollination and how pollen is actually greatly reduced multicellular structure that produces sperm - pollen is actually plant testicles. Plants evolve complex pollen grains, much like the extreme duck penis, to create reproductive barriers between species. The forms of inter-specific (between-species) barriers to reproduction would evolve because those individuals who are more discerning in their choice of mates would waste less time/energy fertilizing and producing those hybrid offspring which are often, at best, viable but infertile but more likely enviable. Often it is the female of the species that is the one who evolves the reproductive challenge for the male because she produces fewer, and often more metabolically expensive, gametes (eggs/ova) than her male (sperm) counterpart and therefore has more to lose if she errs on who she mates with than he.  Public domain image (created by the Dartmouth Electron Microscope Facility) Ultimately we conclude that hybrids exist because Darwin was correct in his model of speciation, that is new species derive from varieties of preexisting species (see Chapter 4 blog post) so they share many of the common genetic traits with their ancestral or closely related species. Surprisingly Darwin did not recognize that hybrids are his best argument against the special creation model of immutable species since one should not expect hybridism to occur between two immutably formed species that were specially created."That's a Wrap" & "Aces High" Kevin MacLeod (incompetech.com) Licensed under Creative Commons: By Attribution 3.0 http://creativecommons.org/licenses/by/3.0/

MANY instincts are so wonderful that their development will probably appear to the reader a difficulty sufficient to overthrow my whole theory. [page 317]In this episode of Discovering Darwin we covered Darwin's chapter on Instinct and how Chuck attempted to explain how animals exhibit complex behaviors that are not learned. More importantly Darwin was trying to outline how behaviors could evolve in the same way he explained the evolution of physical traits.It is not too difficult to study the evolution of physical traits because we often have fossil evidence of their transformation. Last episode we discussed the evolution of whales and the plethora of fossil evidence that has allowed researchers to reconstruct the evolution of the terrestrial ancestor of whales to the streamlined marine mammals we see today. Behaviors are harder to imagine through the lens of natural selection because we can only see those behaviors that are exhibited by extant (living) organisms and behaviors can evolve much faster than physical traits. Cultural evolution can allow individuals within their lifetime to adopt a new behavior that they learn from others. One of the wonderful examples of this is dolphins using a sponge to protect their rostrum (beak) as they hunt for prey in coral structures. They can pass this idea on to other dolphins and you can track the rapid transmission of this behavior through a population. Picture from http://www.livescience.com/21989-dolphin-sponge-tools-culture.htmlDarwin was not interested in learned behaviors in this chapter but he was interested in behaviors that are known at birth or at specific developmental times in the organism's lifespan. Darwin called these behaviors instinct. In exploring this idea Darwin focused on three major examples of innate/instinctual behaviors:1. Cuckoos and their behavior to dump their eggs in other birds nests.2. "Slave making" ants species which capturing of other ant species to become sources of forced labor in their own colonies.3. Honey bees and their complex, mathematically efficient, honeycomb making behavior. CuckooCuckoos exhibit a behavior known as "brood parasitism" where they lay their eggs in the nest of a host species and leave the eggs to be incubated and hatched by the host. The host also raises the cuckoo baby as their own until it is strong enough to fledge from the nest. Below is a dramatic photo showing the poor host Reed Warbler dutifully feeding the ginormous common cuckoo (Cuculus canorus) nestling. "Reed warbler cuckoo" by Per Harald Olsen - Own work. Licensed under CC BY-SA 3.0 via Commons - https://commons.wikimedia.org/wiki/File:Reed_warbler_cuckoo.jpg#/media/File:Reed_warbler_cuckoo.jpgYou may wonder why the Reed warbler does not recognize the cuckoo offspring is not their own offspring? What you are really asking is why has the Reed warbler not evolve the ability to recognize its own offspring from another species? If you were switched at birth in the hospital, do you think your mother would know? What ways do we know our offspring are actually ours? Only through hospital tagging or non-interrupted contact are we to "know" the offspring we have are the ones we gave birth to. Why have we not evolved an ability to recognize our own offspring? Probably because there has not been a selective advantage to recognize our offspring because over evolutionary time it has been rare for humans to be in a situation where we must recognize our newborn from other unrelated newborns. Since that ability is rarely useful, selection has not favored it in our species. In the same manner, birds that nest individually associate those eggs in their nest as being their own. Recognition has not evolved because there is little selective advantage for that ability. However there are birds that do exhibit an amazing ability to discern their own specific offspring among a throng of others. Colonial nesting birds like albatross and penguins have an unerring ability to discern their own chick from maddening crowds because selection has favored that ability.baby penguins awaiting the return of their parents to feed them. Image from Mike Johnson http://www.dailymail.co.uk/travel/travel_news/article-2871252/Tourist-s-incredible-photographs-reveal-stunning-beauty-remote-Antarctic-island-teeming-thousands-penguins-seals.htmlIn nesting birds like the Reed warbler it would normally be rare for it to be stuck raising an unrelated offspring so they have not developed the ability to recognize that the over-sized baby is not really their own offspring. Instead the poor Reed warbler probably thinks she has the largest and healthiest reed warbler baby in the world. Feed it some more!Because nesting birds are less discerning in recognizing their young, brood parasitism has the opportunity to evolve and based upon phylogenetic analysis it seems it has. Brood parasitism has evolved independently seven times in the evolution birds resulting in 75 species out of the 8600 known species of birds exhibiting forms of brood parasitism from occasional indiscretions to those species which never raise their own offspring, instead relying totally on other species to incubate and raise their young. This extreme form of brood parasitism intrigued Charles Darwin in that a cuckoo could be born in a Reed warbler nest, be raised by Reed warblers, fledged from the nest and go off to grow up and retain its identity as a cuckoo bird and not a reed warbler or whomever was its host species. The identity of the cuckoo was innate, instinctual and expressed itself in the adult females when they reached reproductive age.Image from https://whyevolutionistrue.wordpress.com/2011/03/04/mimicry-the-nefarious-cuckoo/Darwin predicted the cuckoo species we see this complex behavior in various stages of complexity, transitions if you will. There are some cuckoos which specialize in parasitizing a single species of birds while other cuckoo species are generalist and parasitize a wide variety of host species. The research suggests it is difficult to discern if the evolution of cuckoo behavior went from specialist (single host species used) to generalist (many potential host species used), or vice versa.  In addition, within the common cuckoo (Cuculus canorus there are families (gentes) who specialize on parasitizing a single host species and the cuckoo egg color has evolved to better mimic their hosts eggs. In the picture below see the cuckoo egg indicated by the arrow in a variety of host nests while showing the great variation in egg coloration within the single species of cuckoo.By what steps the instinct of F. sanguinea originated I will not pretend to conjecture. But as ants, which are not slave-makers will, as I have seen, carry off the pupæ of other species, if scattered near their nests, it is possible that such pupæ originally stored as food might become developed; and the foreign ants thus unintentionally reared would then follow their proper instincts, and do what work they could. If their presence proved useful to the species which had seized them—if it were more advantageous to this species to capture workers than to procreate them—the habit of collecting pupæ, originally for food, might by natural selection be strengthened and rendered permanent for the very different purpose of raising slaves.[page 338]Polyergus mexicanus workers return from a successful raid with captured pupae of the host species, Formica subsericea. Urbana, Illinois, USA Photo from http://www.alexanderwild.com/AntsSarah discussed the intriguing behavior of slave making ants and how Darwin thought it evolved and how modern science has supported, somewhat, his original view. The biggest hurdle for slave making to evolve is that each ant species relies on species-specific and colon-specific pheromones for individuals within a colony to recognize each other. Individuals from other colonies, and even more so, individuals from other species will smell distinctively different from the slave making ants so how do they suppress aggression towards their newly captured indentured pupae?  It was proposed that ants should raid closely related species so that their pheromones are more likely to be similar to reduce aggression between raiders and potential slaves. This is known as the Emery Rule.Interestingly, scientists since Darwin have been studying the evolution of slave making behavior and much is still to be figured out. The closing remarks on a wonderful review paper about the evolution of social parasitism and slave making behavior in ants makes the following observation: "Though slave-making ant species have been studied for more than 150 years, many problems are still open, the most prominent obviously being the evolution of slave  raiding itself. Recent investigations have given contradictory results concerning, for example, the mechanisms of  chemical integration of slave makers and their hosts in a  mixed society, the pattern of sex allocation in slave makers, and coevolution between social parasite and host….Considering that almost all  slave-making ant species are listed as threatened by the  World Conservation Union (IUCN), investigations on  their behavior, population structure, and genetic variability may help us learn more about how endangered they  really are and if and how they can better be protected." (D'Ettorre & Heinze 2001)   Josh ended the program with a discussion of the perfection of honeycombs and how is that bees make such perfect hexagon shapes?stockphoto from http://www.npr.org/sections/krulwich/2013/05/13/183704091/what-is-it-about-bees-and-hexagonsJosh explained that cell shapes within the colony can range from a circular shape to the beautifully distinct hexagon shape we associate with honey bees. Two major hypothesis, which are not mutually exclusive, have been proposed to explain the hexagon shape. The first is the efficiency hypothesis which argues that wax is expensive to produce so bees would evolve to be the most efficient in building their combs and hexagon shape requires the least amount of material and produces the least amount wasted space. PHOTOS BY KATHY KEATLEY GARVEY, UC, DAVISNotice this circular form above has many gaps between the cells in contrast the compact arrangement in the hexagon com.  The second hypothesis Josh brought up was the idea that in the bee hive, the bees body heat melts the wax and the wax then forms a shape that requires less energy to maintain so the straight edges between the cells forms as an outcome of soft wax reaching a low energy resting state.  In this model the bees are not intentionally creating a hexagon shape but it emerges from their constant activity and body heat. It is interesting that the questions that Darwin outlined as interesting issues for evolution are still be investigated and we are beginning to understand these instinctual behaviors better because of the evolutionary framework that Darwin gave us over 150 years ago. The opening theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY Interlude music is Rhapsody In Blue Part 1 by Paul Whiteman and George Gershwin Published 1924 https://archive.org/details/rhapblue11924

In this episode we take a side trip with Dr. Mark Jackson, our colleague from the psychology department, to explore the historical view of instinct behaviors in humans. The next chapter of Darwin's Origin of Species deals specifically with instinct behavior in non-human animals and it stimulated us to question what the thought of the time was considering human instinct behavior. Dr. Jackson brings his sly wit to the conversation and tells us how the early field of psychology dealt with or explained innate behaviors in humans.Mark introduced us to noted historical psychologist William James who is known as offering the first psychology class in the United States and considered the "father of American Psychology".Dr. "Will.i.am" JamesOne of the interesting ideas that we discussed concerning instinctual behaviors in humans is how many of our emotions are frequently intertwined with physical aspects of our bodies. Mark recounted the example of you seeing a bear and how your body may initiate the flight response before your mind can consciously evaluate the situation and determine you are afraid.Unknown man having his legs decide how to deal with the situation before his rationale thought process begins.

In this episode we decided to break from the standard form of the podcast and discuss two chapters at once instead of the traditional single chapter per episode. Episode 7 covers Chapter VI - Difficulties with the Theory and Chapter VII - Miscellaneous Objections to the Theory of Natural Selection. We note that Chapter VII is really more of a vanity press project where Darwin dedicates a whole chapter to personally rebuke the concerns and critiques of Mr. St. George Mivart, a fellow biologist who published criticisms against Origin of Species.St. George Mivart, as Charles Darwin saw him Transitions.  "First, why, if species have descended from other species by fine gradations, do we not everywhere see innumerable transitional forms? Why is not all nature in confusion, instead of the species being, as we see them, well defined?” pg 212James used the imagery of a rainbow to argue that we often ignore the transitions or force transitional forms into the more distinct categories.  The biggest challenge of a transitional form is that it is a challenge that increases exponentially with each attempt to address the lack of transitions. We discussed that if you see Species A and Species C and believe they are closely related then the criticism of lack of transition can be leveled at the evolutionist. If the transitional form Species B is found in the fossil record then the challenge for transitional forms doubles because now you must find the transition between A & B and B & C. Each new transitional form increases the demands for more transitional forms. Sarah made the argument that the transitional challenge is often the case of moving the goal posts.The other challenge of transitional forms is that speciation can occur in two major patterns - anagenesis and cladogenesis. This figure represents the two forms of speciation.figure from http://krupp.wcc.hawaii.edu/In anagenesis the species goes through transformation such that the original form is replaced by the new form and both are recognized as unique species. This shift in form can often occur quickly so that there is little opportunity for fossil evidence of the forms or the transitional forms are quickly replaced by the new forms.Old photographs of common dog breeds show how quickly we have modified the breeds in just 100 years. A summary of this can be found at Science and Dogs website where we collected this intriguing comparison of how the bull terrier has changed over the past 100 years. Of course these are not true species but the premise is the same, shifting from one form to another can occur quickly and no transitional forms remain for comparison. This is where my rainbow metaphor comes to play.The other form of speciation is called cladogenesis which involves a subset of the species that diverge from the ancestral form. Josh spoke about bat bugs and bed bugs and how they share an ancestry but it would be difficult to find the specific transitional individual between bat and bed bugs.image from http://ohioline.osu.edu/hyg-fact/2000/2105a.htmlSaltations"It has been asked by the opponents of such views as I hold, how, for instance, could a land carnivorous animal have been converted into one with aquatic habits; for how could the animal in its transitional state have subsisted? [220]"The evolution of whales, at one time a challenge to Darwin, have now become one of the best examples of evolution. The fossil record for whale evolution is robust because the ancestors of whales were semi-aquatic or aquatic mammals and their remains would often sink to the silty bottom of the ocean or bay where they lived. Buried in the mud the remains would quickly become entombed so their skeletons remained intact. Our current understanding of whale evolution is beautifully represented by this graphic from Berkeley website.A nice video animation summarizes the proposed process of whale evolution and it can be watched here. As Darwin argues, the large differences in forms that we see today developed over long periods of time with successive accumulated changes in form. The scale involved in the process, millions of years with many millions of individuals is often difficult for humans to appreciate or comprehend.James talked about the flying squirrel and how cute it is. Here is his photographic proof of its cuteness. flying squirrel in Kentucky, cutest animal on earth?Complex Structures The eye to this day gives me a cold shudder, but when I think of the fine known gradations, my reason tells me I ought to conquer the cold shudder. - Charles Darwin in a letter to Asa Gray (February 1860).The complexity of the eye with all of its intricate interconnecting parts seem, at first blush, to be too complex to have been formed by natural selection. This has historically been a difficult problem to solve because the eyeball does not fossilize so we are left to look for examples of eye evolution by looking at extant species. However, modern biology using molecular techniques and studying the genes involved in the production of the eye have beautifully reconstructed how a camera-like eye of vertebrates could have evolved from a simple light sensing structure seen in primitive chordates like the hagfish.hagfish with slime - photo from ecouterreThere a nice TED talk with awesome graphics that summarizes our current state of knowledge  of how the eye evolved. The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY Copyright: Attribution-NonCommercial-ShareAlike: http://creativecommons.org/licenses/by-nc-sa/3.0/

In this episode of Discovering Darwin we discussed the fifth chapter of Origin of Species titled Laws of Variation. Ironically there are no laws actually discussed in the chapter but Darwin does outline a variety of phenomenon and patterns of inheritance and variation that puzzled and intrigued him. When we consider the great variation in forms that we see in nature it is often difficult to tease apart the cause of that difference in form. For example, variation in form may be genetically determined as described by Mendel and his experiments with pea plants. Of course Darwin did not have a sense of genes and how multicellular plants (excluding mosses) and animals get two copies of each gene, one form their mother and one from their father, that codes for traits. Those two copies of the genes determine the expression of physical traits. Looking at the chart below of Mendel's pea plant traits you can see how variable the sweet pea plant could be.Imagine Darwin's confusion if he saw pea plants with yellow or green seeds, purple or white flowers and variation on where the flowers are located on the plant. Even more intriguing is the notion that yellow seeded pea plants with purple flowers could be crossed and produce offspring with green colored pea seeds and white flowers! Today, with our knowledge of genetics, we understand the concept of recessive and dominant traits and how recessive traits can be hidden in the parents but expressed in the offspring when they inherit only the recessive versions of the gene.We discussed if Darwin actually was aware of Mendel's work and Josh mentioned an interesting paper by Bizzo and El-Hani that argued Darwin was aware of Mendel's work. That paper can be found here.Acclimation versus AdaptationSarah discussed how Darwin seemed to use the terms acclimation and adaptation interchangeably as he worked through his understanding of how organisms can exhibit variation in form. Today biologists see these two concepts as separate and unique characteristics.Some of the best examples of acclimation can be seen in arctic animals, like this arctic fox, that can dramatically change their coats from winter to summer. Acclimation is when the organism alters its form, physiology or behavior in response to local environmental conditions. Often these changes are induced by hormonal changes in the organism which themselves are triggered by environmental stimuli.  These changes are typically not permanent.In contrast, if you look at a population of a species you may see variation in forms but these are adaptations to local conditions. An interesting example of local adaptations is seen in the north American rock pocket mouse (Chaetodipus intermedius) that lives in the southwest desert areas of US and Mexico. This small, bite sized rodent, lives in a variety of rocky habitats which differ in color depending upon the geological history. The brown sandy colored rocks are in contrast to the black balsaltic rock that formed from geologically recent lava flow events. The mice have strong local selection to avoid being seen by their natural predators so selection favors coat colors that blend with the background. The top two images are showing the local mouse in its native local condition, the bottom two panels are swapping mice from their native locations. All of these mice are the same species but their coat color variation is genetically determined by expression of Mc1r gene for black pigmentation and that gene has undergone local mutations and selection. http://uanews.org/story/coats-different-color-desert-mice-offer-new-lessons-survival-fittest  We also discussed how creatures locally adapt to caves by losing the ability to see and often become pale colored or completely lose their coloration.  Josh read a wonderful quote by Darwin where he described blind cave crabs possessing components of the eye but it was incomplete in form.Image from http://imgarcade.com/1/blind-cave-crabWe also discussed how Darwin recognized the pattern that certain traits correlated with individual sexes but did not understand how that was possible. Darwin spoke of calico cats and how he was puzzled that they are typically only female.  Of course we now understand that sex is determined by sex chromosomes and traits can be sex-linked when they are located on the sex chromosome, which in mammals are called X and Y chromosomes (females are XX, males are XY).A very nice summary of the genetics of calico cats can be found here.image from WikipediaDuring the podcast we discussed Darwin's critique of the idea that every unique species was individually specially created by a Creator. Darwin mentioned how improbable it was that the creator would take the time to make different varieties of turnips. This discussion stimulated a flashback for Josh to remember when he was an undergraduate seeing outside a professors office a classic Farside cartoon concerning special creation. "Oh my, me...." copyright Gary LarsonModern View of Inheritance and Sources of Genetic VariationIn contrast to Darwin's semi-blending model of inheritance, biologist today rely on the particulate model of inheritance, which is based on the idea that individuals gain specific set of genetic particles (chromosomes) from both their parents. We now understand that the process of sexual reproduction creates great variation in offspring without relying solely on the process of genetic mutations to create new forms.Yes genetic mutations are important in creating new traits (see mouse story above) but much of the genetic variation we see in nature within a generation derives from shuffling and recombining preexisting traits when creating gametes (eggs and sperm) and combining those gametes (fertilization) into a new individual.To illustrate how variation is created through sexual reproduction allow me to use an analogy where playing cards represent genetic information. Imagine you take a complete deck of cards sans the joker and partition them out such that you have all the heart and spade suits and your reproductive partner has all the diamonds and club suits. The red colored suits (diamonds and hearts) represent the original genetic material inherited from your mother's side and the black suits (clubs and spades) denote the original genetic material inherited from the father's side.  Each of these cards would signify a chromosome, a strand of DNA that has a variety of genes which code for traits. Since you would have two copies of each chromosome - a heart and spade set of ace, 2, 3, 4, 5, 6, 7, 8, 9, 10, jack, queen and king - you are considered a diploid (di - two) individual. So is your reproductive partner who has the diamond and club suit of the same cards. In this example you would have a total chromosome count of only 26 where in reality humans have a total chromosome count of 46 but this simplified example will illustrate how inheritance and a majority of the variation occurs.Your diploid genome - 1/2 the genetic material from your dad, 1/2 from your mom.When you go to reproduce sexually you make gamete cells, either sperm or eggs depending upon your biological sex. To make those cells you randomly draw a single card from either the heart or spade suit to create a cell that has only one copy of each card - ace through king. This new cell would have a chromosome count of only 13, half of what you have, and is called a haploid cell. Your partner is doing the same thing with their cards, creating a haploid cell that contains ace through king cards randomly chosen from the diamond and club set they contain. When those two haploid cells fuse, a process called fertilization, you recreate a diploid individual who has two copies of each of the cards ace through king. So in sexual reproduction it is a reduction in total genetic material (in haploid gametes) and then a reconstitution of the total genetic material during fertilization.The traits encoded in the genes on the chromosome, represented by the playing cards, get passed from parent to offspring as intake distinct "particles". Variation is also created in this process because when the gametes are formed the single chromosome donated to the cell came about from randomly drawing from the two possible sources. Imagine you are actually flipping a coin to decide which card to choose with the rule that heads picks the red card and tails picks the black card. You could randomly draw all the red cards to make your gamete, improbable but not impossible. It would require flipping 13 heads in a row which for a fair coin the probability of occurring is 1 out of 8192 times.  Improbable but not impossible. The inverse is true for drawing only black cards. Most likely the gamete would contain a mixture of red and black cards for the ace through king cards.  But even then, you could create a large number of possible combinations of just those thirteen cards - 8192 to be exact. You then repeat the process for the other gamete and it is easy to see how many different combinations of chromosome pairs the new fertilized gamete can contain. This process of creating genetic variation through random drawing of each chromosome is called independent assortment, that is each chromosome independently assorts into the gamete cell.One of 8192 possible haploid gametes you could makeAs you imagine all the probable outcomes of creating this gamete it becomes clear that you could create a great diversity of gametes - in humans with 23 pairs of chromosomes you can create 223=8,388,608 genetically different gametes! On top of this source of variation, there is also a phenomenon called crossing over where two sister chromosomes - in our example imagine two of the cards of the same value, e.g., the queen cards - break apart and recombine with each other. So take your queen of hearts and queen of spades, stack them together, rip them randomly in two and then tape the two opposite colored halves back together to create a queen card that now has top half red and bottom half black and the other card is the inverse, top half black and bottom half red. This would then allow traits on one chromosome to be combined with traits on a completely separate chromosome so they are now being inherited together. Assuming these traits were housed on the same chromosome, which is not true, imagine grandma had brown eyes and was farsighted, whereas grandpa had blue eyes but had normal vision and all of these traits were on the same chromosome. Now with crossing over, we have a chromosome with grandmas brown eyes and grandpas normal vision and grandpas blues eyes now combined with farsightedness. A crude approximation of crossing over creating two new chromosomes.As you can see with crossing over and independent assortment occurring you can appreciate the great array of genetic diversity that can be created in the offspring during sexual reproduction.The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh. http://freemusicarchive.org/music/Balogh/Revitalized_Eyes/MAY Copyright: Attribution-NonCommercial-ShareAlike: http://creativecommons.org/licenses/by-nc-sa/3.0/  Interlude music if Frenchy's String Band "Sunshine Special" recorded in Texas sometime around 1927. https://archive.org/details/FrenchysStringBand-SunshineSpecial 

As we thought, this became the longest episode we have recorded yet but then again, we had a lot to cover. Chapter IV is the part of Origin of Species where Darwin outlines how he believes natural selection, over long periods of time, can generate new species. It is a rich and complex chapter and our wide-ranging conversation explored a large number of the issues Darwin brings forth in the chapter.We discussed at great length the variety of ideas that Darwin encapsulates within the only figure in the book. James mentioned how Darwin first sketched the figure in his notebook B - Transmutation of Species with the understated "I think" title followed with "Case must be that one generation then should be as many living as now. To do this & to have many species in same genus (as is) requires extinction. Thus between A & B immense gap of relation. C & B the finest gradation, B & D rather greater distinction."   Image from Original Notebook at Darwin Online. Ultimately this image became refined for Origin of Species to look like this -In our discussion we noted that this image represents ideas like: a large number of extinction events, the lack of predictable direction in evolutionary change, no change (E & F), increase in species numbers, differential rates of evolution as indicated by the slope of the lines radiating out at a specified time era (e.g., era IV, z4), and that species can converge in character traits (e.g., how f lineage shifts to look like extinct d lineage). A larger version of the figure can be found here. Sarah noted how human evolution phylogenetic tree can show the same sort of pruned bushiness that Darwin represented in his figure. This figure is from the Smithsonian and is an interactive figure at their site that is worth checking out.Interestingly there has been recent researchers who reject the evolutionary tree model for human evolution. Instead of the classic tree structure they note that the mitochondrial DNA (mtDNA) analysis suggests all modern humans can be traced back to African ancestors who dispersed out of Africa only 100,000 years ago. However, those various subspecies of humans interbred and migrated back into Africa thereby creating a more reticulated, "trellis" evolutionary relationship than the classic branching independent lineages as represented in a tree. Follow this link to read a nice summary of the alternative view with a figure to illustrate the trellis view of human evolution. Sarah mentioned how quickly other scientists adopted Darwin's tree model to represent relatedness and she noted how the embryologist Ernst Haeckel drew up a phenomenal evolutionary tree. To truly appreciate this tree  you should see it in a larger format. We also discussed the rapid evolution of the Hawthorn maggot fly and its shift to feeding on introduced Apples and how that resulted in two populations with little genetic exchange between them. It is a beautiful house fly sized insect with painted wings which they flick to mimic the movement of jumping spiders. Photo Copyright © 2013 Harvey Schmidthttp://bugguide.net/node/view/817659Do you see the jumping spider in its wings?At the end of the podcast we attempted to read the epic opening sentence in Darwin's summary in a way that brings the words to life. Here it is for you to try.If under changing conditions of life organic beings present individual differences in almost every part of their structure, and this cannot be disputed; if there be, owing to their geometrical rate of increase, a severe struggle for life at some age, season, or year, and this certainly cannot be disputed; then, considering the infinite complexity of the relations of all organic beings to each other and to their conditions of life, causing an infinite diversity in structure, constitution, and habits, to be advantageous to them, it would be a most extraordinary fact if no variations had ever occurred useful to each being's own welfare, in the same manner as so many variations have occurred useful to man.