“The more complex and sophisticated a social system is,” she writes, “the more likely it is to have homosexuality intermixed with heterosexuality.”It's an hypothesis, but I'll only go as far as treating it as one among many. Roughgarden is adamant, though:
“I’m convinced that in 50 years, the gay-straight dichotomy will dissolve. I think it just takes too much social energy to preserve. All this campy, flamboyant behavior: It’s just such hard work.”That'll be the day! The bet is on. I'll even go as far as ridicule: You must be joking!? In 50 years the continuum of sexual behavior is so ubiquitous that the extremes are the oddities? Not bloody likely.
And there are plenty of hypotheses to explain homosexual behavior. And none of them challenge sexual selection. If I may quote from one of my own posts:
Adaptive explanations: Social glue, Intrasexual conflict, Practice, Kin selection, Indirect insemination, Overdominance, Sexually antagonistic selectionPeacocks:
Non-adaptive explanations: Mistaken identity, Prison effect, Evolutionary byproduct, Maladaptation, Infection
Roughgarden’s cataloging of sexual diversity has challenged a fundamental biological theory. If Darwinian sexual selection—whatever its current variant—is to survive, it must adapt to this new data and come up with convincing explanations for why a host of animals just aren’t like peacocks.It's the classical example, and from personal observation, I think we've all gotten the peacock wrong, by the way. The story is that the male peacock's tail-feathers are so flamboyant in order to attract females, but that they increase the risk of getting taken by predators. The choice of the females drives sexual selection, and the males that get to mate are the ones with the biggest feathers. However, for me to be convinced that this is true, two things must be shown to me. 1) That predators really have an easier time catching the sexiest males, and 2) that the male peacocks I have seen showing off their feathers to admiring humans who get very close are actually sexually interested in mating with the humans (I'm not being ironic - this is totally possible). I will venture a guess that the first isn't really true, because the second phenomenon occurs because the male is trying to scare off the humans/predators. And perhaps scaring predators works best when you have huge feathers. There are other species who try to scare off predators by faking size:
Do you know of any other examples?
Thanks for taking on this article. I am most definitely not an evolutionary biologist (heck, I'm not even a scientist; I'm a lowly engineer!) but where I read Roughgarden's article it seemed mighty fishy. I sympathize with her intentions, but the article just didn't make any damn sense to me.
ReplyDeleteIn regard of the peacock's tail, maybe the 'eyes' have it? I mean, if, as I've read, the 'eyespots' on some animals are supposed to confuse a potential preditor, why would a whole bunch of eyes not suggest to a p.p. that it's out-numbered, move along, the eating is safer somewhere else?
ReplyDeletecicely
Cicely, that's a great point. I'll buy that. Thanks. From now on I will comment this whenever anyone talks about peacock tails.
ReplyDeleteAlso, are there any computer models that depict an image of a peacocks fanned out tail from the perspective of any of it's potential predators? The tail may look substantially different to a bobcat than to us, and I'm sure it looks much more dazzling to other peacocks based on what little I know about the spectrum of bird vision.
ReplyDeleteI'm the guy who commented on another blog post that Lord Stern got carried away bending facts, most likely because he is a fervent subscriber to a vegetarian diet. Not that there is anything wrong with it, just don't let your passion cloud your scientific judgment.
ReplyDeleteWhat does this have to do with Joan Roughgarden, an eminent scientist in her field? She used to be John Roughgarden, an eminent scientist in his field. Not that there is anything wrong with that, but don't let your passion.....
She did of course get comments raising that concern, and replied that she is merely looking to explain the data in a way that sexual selection doesn't. I remain unconvinced (and annoyed by the insistence on an adaptationist approach), and have of course also pondered is her judgment is clouded because of the sex-change.
ReplyDeleteI remember learning something in first year along the lines of "evolution drives females to pick the males with the most [insert favourite adjective] [insert character of choice] as this [adj][character] is costly, and thus means the male's genes are good enough to compensate for it". I may have even read this in Selfish Gene, although don't quote me on that. And I never really...got it, I guess. It reeks of intricate mental gymnastics.
ReplyDeleteWouldn't it be much simpler to describe this as a hyperstimulation thing, a la Tinbergen's dotted bird beaks? If a female (male too, but they don't pick, usually) has some attraction towards a particular feature for whatever reason (could be just a glitch), then naturally it would be adaptive for males to enhance that feature, even if there is no real advantage besides just that. This doesn't have to carry any advantage to the female either, nor does it say anything about the 'quality' of the male's genes.
Besides that, the peacock tail as scaring away predators idea is quite appealing as well. Makes sense, and quite simple too.
I don't see how sex selection is anything fundamentally different from your garden variety natural selection. Why should it be? Most things don't have sex!
As for female mate choice, the trait they choose on can be either costly or not for the males. In the case of peacocks, if there was no other advantage to having huge tail feathers (which I think is not the case), then sexual selection for them would most likely be assessing a real cost to the males.
ReplyDeleteIn the case of blue- and red-footed boobies (always an enjoyable term to google), females may or may not be assessing a real cost to the males, but why females of one species prefer red and the other blue is hard to explain outside of sexual selection, I think.
Natural selection is an umbrella term that can be divided into several forms of selection, and sexual selection is just one of them, though it does have its peculiarities.