The peacocks magnificent tail is the most famous example of this [sexual selection]. It did not evolve for natural survival. In fact, it goes against natural survival. No, the peacock's tail results from the mating choices made by peahens.I've said it somewhere before, but I'll just go on and say it as many times as the editor* of this blog allows me: THE PEACOCK'S TAIL SCARES AWAY PREDATORS! (I'm told all-caps gets the message across).
Now, I admit immediately that this is not a well tested hypothesis. Here are the two pieces of evidence that I have: I have myself seen a peacock raise its tail** in San Diego Zoo when it was approached by... children. They were going too close, and as a result it raised its tail feathers (yeah, I know, correlation/causation - maybe the peacock was horny at the sight of humans its own size).
Another is a story I've heard about a peacock in a garden and two golden retrievers. The first time the dogs saw the bird, they ran barking towards it, and in response (or, again, just maybe because it was at that very moment getting all horny thinking about a certain peahen it had met earlier that morning) it raised its feathers. And the dogs cowered and retreated, and never bothered the bird again.
In addition, I have also once heard that eyes generally confuse animals, which might be why there are "eyes" on the feathers. And of course, if you can fool the predator into thinking you're the bigger one, they may just forget about the peacock meal.
The story for how the tails would increase the likelihood that a predator catches the peacock usually describes a peacock on the run, with the tail feather in the "neutral" position, and the predator grabbing on to the long feathers. But that of course only works if the peacock retreats in the first place.
Now for some testing. Next time you see a peacock somewhere (zoos, public gardens - there are many in California, but I haven't seen any here in Michigan - or did I see one in Detroit Zoo?), try to ask a child to approach it too closely and see what happens. If you're against involving children in research (why would that be?), get down on all fours yourself. Tell me what happens.
And here we damn well go:
And here is a great dramatization of a peacock scaring off a pesky dog.
And here's one interacting with humans.
Lastly, I do not at all contest that sexual selection is also involved. It is unlikely the the peacocks fan their tails at peahens in order to scare them away.
Dutton's talk, by the way, is about a Darwinian theory of beauty. Watch it here, if you must.
* Fortunately, that's also me.
** Okay, so it's also called a "train", and those feathers are not on the tail at all, but "highly elongated upper tail coverts." [Source.]