I’ve been watching ducks recently. Mallard ducks show the remarkable difference beteen the fairly drab female and the quite glamorous male. Is this just another case of an unfair asymmetry in nature?
Maybe not. An opposing proposal is that what we are seeing is the effect of female avian aesthetics. Females are generally those who select the partner in a pair. What we see is the effect of their taste, shared to some extent by females of at least one other species. Namely, human beings.
Another interesting fact is that female aesthetic preference does not always pick out the fitter male bird, fitter, that is, in birdly things like flight. In fact, it very much looks as though the song of one species is improved by wing configurations that, when increased, create a bird less capable of good flying.
Yale Professor Richard O. Prum argues, as it is put, that sexual selection, unlike natural selection, is not always selection of the fittest. In fact, he thinks it is based on female avian sexual aesthetics.
To grasp his view, a little bit of history is in order. Darwin famously proposed the idea of evolution by natural selection, what is often called survival of the fittest. To put it simply, living things vary in their inherited traits, from speed to color to sense of smell. The traits of the individuals who survive longer and have the most offspring become more common. So, over time, the faster antelope have more young, the fastest of them have more offspring, and antelope end up very speedy.
But reproduction isn’t just about surviving and staying healthy long enough to mate. You have to find a mate. And in many species, your mate must choose you. This process is sexual selection. Female birds are often the ones choosing. And their choices can produce male birds that are incredibly colorful, and some that are elaborate dancers or designers of striking boudoirs — like the bower birds. If, for example, females like males with long tails, then long-tailed males have more offspring, and the longest-tailed of those offspring reproduce more. In the end, that species becomes known for its long tails.
Whether he is generally right, there do seem to be cases of sexual selection that can degrade the species. What does this say about the survival of the fittest?
Crudely natural selection is supposed to select for those who meet the challenges in their environment in a way that enhances reproductive success. But if we include getting selected as a mate, then overall fitness need not be enhanced in the species. Or so two articles in the NY Times seem to suggest. See here and here. To be accurate, though, I don’t think anyone writing sees any problem in distinguishing natural from sexual selection. Justifying the distinction is another matter, or so Professor Prum’s reference to free will for female birds could indicate. See the end of the second article:
Once organisms evolve the capacity for subjective evaluation, and the freedom of choice, then animals become agents in their own evolution. One of the hallmarks of autonomy, of course, is the freedom to mess up