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 birds
Mark 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 Miller

Rainbow darter male

Mark 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 mane
We 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