Wednesday, February 13, 2008

About beautiful men (or the lack thereof)

A male blue headed rock thrush

I look up around me at mess and there's no one there that catches my eye anymore. I find I'm surrounded by all the drab greys, browns, blues and khakis that constitute Indian academic camouflage. I ask myself every once in a while, what happened to the human species?

One of the things that often gave Darwin pause was the sheer flamboyance of some male animals. Many male birds are spectacularly coloured, much more so than their female counterparts. Take the male blue-headed rock thrush, all bright blues and oranges, flashy white wing patches. The female on the other hand is this beautiful mottled muted brown, disappearing in the undergrowth.

A female blue headed rock thrush
Now being drab, muted and camouflaged is obviously a good thing in the wild world. Less attention is good when one negotiates a world fraught with constant predator threat. So why all the male flashiness? Whose attention are they seeking? Ok, I know, its the females, that much is obvious.

But why would a sensible female be interested in a flashy flamboyant male? Why are these traits at all desirable for her offspring? Why would a female want to raise predator bait? You can see the problem there, can't you? The exaggerated and beautiful traits of males cannot be explained under the standard framework of standard adaptive natural selection. If you suspect that maladaptiveness, even complete uselessness of these traits, take a look at Wallace's birds of paradise, 1, 2 you will be convinced. What do birds want with all those bells and whistles, streamers and bright colours, other than to impress females? Not much. But what do the females want with them?

A male paradise flycatcher in breeding plumage

There are at least two theoretical frameworks that might explain the appearance of such traits through the process of sexual selection, R A Fisher's runaway selection hypothesis and Amotz Zahavi's handicap principle. Both of them suggest different mechanisms for the same process.

Fisher suggested that if preferred even slightly more exuberant displays than those of most males (which they might for either some quirky in their genetics or due to correlation (not necessarily causal links) with good genes), they would mate with males with these kinds of displays. And competition among males for these females would give rise to more and more exaggerated traits until standard natural selection stopped the process from escalating. The idea is roughly the preference would set up a positive feedback loop feedback which would make the selection in a sense run away with itself, hence runaway selection.

A female paradise flycatcher

The other idea, which I love, because it's so seemingly audacious and because its proposer is, is the handicap principle. I have blogged about Zahavi's idea before. Put shortly the idea is that males with exuberant displays are like people who give themselves a handicap in a race, go ahead says the man I will begin 5 minutes after you and I will still beat you! The animal signals the 'goodness' of his genes by surviving despite his handicap and hence a female must want those genes. The crucial thing about the handicap principle is that the signal needs to be honest, it should not fake-able. To have the long tail must be a real cost and a weak male with the tail should suffer or, well, die! The Fisherian view does not have this requirement. And this is a good thing, because we have a criteria then that might allow us to ask with clever experiments which of two possible mechanisms are at play in a particular system.

Is human male flamboyance easily fake-able (anyone can buy flashy clothes) hence useless? Or are human females just less choosy about appearance and do we prefer exaggeration elsewhere?

Now, now, I was thinking bank balances....

Aside: Since my last post was a 'say hello' post, this one is going to be a 'thank you'. Thanks to the many folks who've linked to my blog and said so many nice things! Abi, Rahul, Brian, and Stephen. I don't know everyone who's ever linked but you know who you are, thank you.

3 comments:

Rohini Kamath said...

Hi Natasha,

I often read your blog. I was first led to your post when I was searching for the migration time of Rosy pastors about a year or so ago.

I enjoy your posts, all the best!

Anonymous said...

Your pictures are really cool.Why do you mostly do pictures of birds?

ZT,Mr.Lewis's reading group

Natasha said...

Hi ZT, Glad you like the pictures. I didn't realize that I was using a lot of bird images till you pointed it out.

The place where I live and take pictures is a small place, and its a bit urban. So there are no large animals (mammals), mostly insects and birds, and many of these. So I guess my pictures end up being skewed towards the birds end.

But thanks for pointing it out and I will remember to add more insects at the very least!