Darwin’s Theory of sexual selection finally liberated from the “adaptationists”

There have been two very exciting events in the world of human evolution over the past month. First is Yale ornithologist, Richard Prum’s The Evolution of Beauty: How Darwin’s Forgotten Theory of Mate Choice Shapes the Animal World – and Us. Here is my review on his Amazon page:

The Evolution of Beauty This is the most significant book about human evolution to come along in a very long time. Most popular classics in the genre are by very good science writers, like Matt Ridley (Red Queen), Robert Wright (The Moral Animal), or even Richard Dawkins (Selfish Gene). The Evolution of Beauty easily matches the popular appeal of those books, but it is also in a class with E. O. Wilson’s Sociobiology (which ultimately opened up Darwin’s other taboo idea of group selection) for opening up the field of sexual selection. Here is a first rate naturalist (ornithology) authoritatively sweeping all the accumulated detritus off of Darwin’s most brilliant deduction: that the peacock’s tail has nothing to do with natural selection, but is solely driven by the peahen’s evolved taste for the beauty of the tail. Then Dr. Prum takes you on a fascinating journey demonstrating the thrilling power of this long-suppressed idea to enlighten disparate aspects of human nature. Some might think his ideas might go over the top in the second part of the book, but in my judgement, Prum doesn’t even scratch the surface of the depth to which sexual selection has influenced human evolution.

Someone correctly took issue with my characterization of the idea of sexual selection having been “suppressed,” and also criticized what could be interpreted as implying conspiracy in one of Dr. Prums chapter headings: “The One Forbidden Truth.”

I responded with this:

Perhaps my post was a bit too condemnatory in my characterization of “suppressing” sexual selection. It is more that it hasn’t been accepted for the astoundingly radical theory that Darwin proposed: I don’t know of a researcher that has embraced Darwin’s insight that sexual selection has nothing whatsoever to do with natural selection, and that it is solely the peahen’s co-evolved taste for beauty that selects the peacock’s tail. Researchers have not been able to accept that there isn’t some sort of naturally selected adaption involved in the process. Dr. Prum’s book’s real value is the authority – and skill – with which he, one by one, dispatches the “adaptionist” notions, like the “handicap” theory. I really think it is a very important book and recommend it highly. I do think that Darwin’s version of sexual selection has not been accepted, at least partially, because it would allow the camel’s nose back under the tent of: both ideal Platonic forms (beauty), and Aristotelian teleology (beauty as a final cause), both ancient and venerable ideas that have been “forbidden” in academic circles for 150 years.

300,000 year old fossils found in Morocco that have distinctly modern Homo sapiens traits

The second significant event is the publishing of a study of fossils found in West African Morocco (instead of the usual East African rift valley), that have been accurately dated to be over 300,000 years old. The big news is not just the early date and where it was found, but that it has a “mosaic” of archaic features and modern features as outlined below taken from the excellent article in Nature:  a)early Neanderthal, b) late Neanderthal, c) early H. sapiens (Moroccan), d) modern human. Note that delicate cheekbones are typical modern human features. 

Ancient human skulls. . . And how they are related

I have long thought that the primary modus of Homo sapiens evolution has been by sexual selection, just as Richard Prum describes it in his book. For example one of the major changes noted above is from an “elongated” braincase to a “globular” one with a “small face.” I am not alone in thinking that the change in braincase had nothing to do with being smarter, but rather with looking more like a cute baby. Sexual selection for looking (and acting) younger is a well- known phenomenon in evolution (called neoteny), and we are so immersed in in it we don’t even notice it.

Below: Pan is a chimpnazee. Note the similarity of infant chimp and adult Homo sapiens: both have small faces and globular heads.




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