Wednesday, May 31, 2017

Useless Beauty

One characteristic of living things that has thrilled everyone who has ever considered it is the astonishing level of beauty they exhibit. Consider, as an example, this bird of paradise:

or this blue dachnis:

Why are living things like birds and butterflies so beautiful? Darwin thought that females selected mates based on their fitness and that this sex selection caused beauty to evolve as a by-product. This is still the reigning explanation today (although it doesn't explain the beauty of flowers), but as an article by Adrian Barnett at New Scientist explains, not everyone is on board with this explanation, maybe not even Darwin himself. Here's an excerpt:
“The sight of a feather in a peacock’s tail… makes me sick,” wrote Darwin, worrying about how structures we consider beautiful might come to exist in nature. The view nowadays is that ornaments such as the peacock’s stunning train, the splendid plumes of birds of paradise, bowerbirds’ love nests, deer antlers, fins on guppies and just about everything to do with the mandarin goby are indications of male quality.

In such species, females choose males with features that indicate resistance to parasites (shapes go wonky, colours go flat if a male isn’t immunologically buff) or skill at foraging (antlers need lots of calcium, bowers lots of time).

But in other cases, the evolutionary handicap principle applies, and the fact it’s hard to stay alive while possessing a huge or brightly coloured attraction becomes the reason for the visual pizzazz. And when this process occasionally goes a bit mad, and ever bigger or brasher becomes synonymous with ever better, then the object of female fixation undergoes runaway selection until physiology or predation steps in to set limits.

What unites these explanations is that they are all generally credited to Darwin and his book The Descent of Man, and Selection in Relation to Sex. Here, biologists say, having set out his adaptationist stall in On the Origin of Species, Darwin proposed female choice as the driving force behind much of the animal world’s visual exuberance.

And then along comes Richard Prum to tell you there’s more to it than that. Prum is an ornithology professor at Yale University and a world authority on manakins, a group of sparrow-sized birds whose dazzling males perform mate-attracting gymnastics on branches in the understories of Central and South American forests. Years of watching the males carry on until they nearly collapsed convinced him that much of the selection is linked to nothing except a female love of beauty itself, that the only force pushing things forward is female appreciation. This, he says, has nothing to do with functionality: it is pure aesthetic evolution, with “the potential to evolve arbitrary and useless beauty”.(emphasis mine)

As Prum recounts, this idea has not found the greatest favour in academic circles. But, as he makes plain, he’s not alone. Once again, it seems Darwin got there first, writing in Descent that “the most refined beauty may serve as a sexual charm, and for no other purpose”. The problem is, it seems, that we all think we know Darwin. In fact, few of us go back to the original, instead taking for granted what other people say he said. In this case, it seems to have created a bit of validation by wish fulfilment: Darwin’s views on sexual selection, Prum says, have been “laundered, re-tailored and cleaned-up for ideological purity”.
The difficulty here, at least for me, is that it doesn't explain why animals would have developed a sense of beauty in the first place. Pair-bonding and reproduction certainly don't require it, obviously, since many organisms, including humans it must be said, successfully reproduce without benefit of physical attractiveness. So why would some organisms evolve a dependence upon it, and what is it in the organism's genotype that governs this aesthetic sense?

Could it be that animals, or at least some of them, are intelligently designed to just delight in beauty?