The Evolution of Beauty: How Darwin's Forgotten Theory of Mate Choice Shapes the Animal World -- An Us by Richard O. Prum is one of those books like
Guns, Germs, and Steel . . . it's so well argued and supported and compelling and significant that it might change everyone's brain; I'm not an evolutionary biologist, so it was easy enough for me to buy Prum's theory-- but apparently there are some old school hold-outs that aren't done with their holding out (I guess if you die while still holding out, you never have to acknowledge you were wrong) but basically Prum argues that Darwin theorized about
two kinds of selection and one of them has been tragically long neglected and ignored:
1) everyone knows about natural selection . . . the grinding statistical journey that a species embarks on in order to survive in an ecosystem . . . if you've read
The Selfish Gene by Richard Dawkins then you know how this works: the goal isn't necessarily to be "red in tooth and claw" but simply to do anything as an organism that makes your genes get to the next generation-- you can be a shark or a lichen or an ant or human, cooperate or kill, hide or clone yourself, become parasitic or symbiotic, whatever works;
2) then there is
sexual selection . . . and Prum argues that-- for various reasons, some cultural, some intellectual, some political, some uglier-- sexual selection has been conflated with natural selection, and hard-core natural selection advocates argue that mate choice is always connected to fitness, but Prum-- an renowned ornithologist-- sees it differently (or more like Darwin) and argues that sexual selection is often aesthetic and totally disconnected from a species fitness, and the ornamental physical features and mating displays (of which the peacock's tail is the most famous) are the result of a runaway feedback loop of sexual selection and can be contrary or detached from the fitness of the species to survive;
the old way to interpret this is the handicap system-- if a male peacock can support a big crazy tail
and survive then "wow!" this bird must be really really fit and females are choosing the big tail based on that criteria but this handicap idea just doesn't hold up-- creatures would then have costlier and costlier ornaments, that would cancel out fitness-- he uses the
"With a Name Like Flucker's, It's Got to Be Good" SNL skit to illustrate the logical problem with the handicap system of selection . . . but you could also imagine that a trait like acne would then be sexually attractive in humans, because it does indicate hormonal fitness to mate and it is a handicap but it's not selected for sexually-- the peacock's tail is on a separate loop from fitness, and it is based on female choice-- which was the big political problem with Darwin's theory of sexual selection-- it gives females autonomy and a decent amount of control in how a species evolves . . . folks were able to swallow one part of Darwin's idea-- male vs. male mating rituals . . . because when a couple of elk butt heads you can imagine that they are demonstrating physical fitness, a trait that could be significant to survival, but when a female bowerbird peruses the male's blue bedecked bower and decides that it seems safe to investigate, that's giving the female too much power in an aesthetic pathway that is rather arbitrary and not linked precisely to genetic fitness . . .
many many years ago I made a terrible choice for a presentation topic at a job interview-- the evolution of the wing-- this always fascinated me: what good is half a wing? but the theories that were prevalent in the early 90's said that each step of the way the wing was naturally selected-- there were heat collecting benefits to half a wing and gliding potential and the possibility of looking bigger than you were . . . but now there is evidence that feathers
preceded the wing on the evolutionary timescale and that they might have been selected for-- as happens with the Argus pheasant--
because they are beautiful and the wing evolved from there-- so it started as a sexually selected trait and then became genetically useful to the species and thus naturally selected for . . . this is a lot to think about, especially since evolutionary biology was developed in a period where Prum claims "every professional geneticist and evolutionary biologist in the United States and Europe was either an ardent proponent of eugenics, a dedicated participant in eugenic social programs, or a happy fellow traveler" but we now know that people certainly don't make their mating choices based on genetic fitness-- sturdy women with wide hips and strong ankles and wrists are what the eugenic proponents recommended-- in fact, mating choices changes with the times and the place and the context: so you can have "heroin chic" European models and nearly obese Khoisan women and both are considered incredibly attractive in their culture . . . we're not doing eugenic calculation in our brain, we simply find someone or something beautiful, and Prum believes the birds he observes operate in the same manner, and then when you've found something beautiful and you mate with it, your children will have a genetic predilection to find the same things beautiful and increase the likelihood of that trait being propagated, even if it's not the most utilitarian thing for the genetic survival of the species as a whole . . . and a few million years of this arbitrary wackiness and you've got the peacock's tail (which was so absurd that it made Darwin sick) but the same could be said about human female breast tissue-- humans are the sole animals that keep this tissue year-round-- and it drives some men wild . . . but really offers no genetic fitness, it's much more convenient to just have temporary breast tissue (as women with big boobs who play sports must know all too well) and that's how the rest of the mammals do it, but this isn't a "mistake," it's a trait that has been sexually selected for and offers nothing but attraction and beauty . . . and this theory also explains why we find art beautiful and music, because we have the capacity to find things beautiful, and so do animals, and that choice-- which is politically charged and intellectually difficult-- is what fuels this other type of selection: Prum explains that it was easier to just have one method of selection, and think about everything through that lens, but it just doesn't make sense for a lot of behaviors and traits . . . so I highly recommend this book, it's a big one and it will change how scientists view the world, there are detailed descriptions of bird mating rituals that you can skim, but it's generally an easy and compelling read and the ideas are ground-breaking.
