If all you want to do is show that sexual selection is happening right now, today, you could just do option one: measure the reproductive success of beautiful people vs nonbeautiful people. If you want to prove the more difficult proposition that sexual selection has been strong enough, for long enough, and consistently enough to be an actual force, you’d have to do option two, or something similar. As far as I know, the only way to prove past evolutionary pressure is to use population genetics as I mentioned. The GWAS is just to help you figure out which genes to look at. There are other ways of doing that.
I’m completely unclear here. What was Darwin doing, then, given that he had no recourse to population genetics?
There’s a difference between what Darwin did - proposing evolution by natural selection as the driving force for the changes and adaptations we see in the world around us - and what we’re talking about - proving that one specific trait in one specific organism is the result of one specific subtype of evolutionary pressure.
bump: very cool! This is something that either wasn’t covered in my old physical anthropology classes, or else I was asleep that day. Thank you!
Smeghead: I don’t think I agree. Darwin looked at some very specific evolutionary “causes and effects.” He studied the beaks on finches and the plumage of pigeons, for instance, without access to genetic data – or even the knowledge of genes themselves.
(What most amazes me about Darwin is that he was able to demonstrate the “granularity” of heritage, and to show that there had to be discrete “objects” that controlled heredity of physical traits, all simply from observing the transmission of traits over generations in animals. He was well on the way to a mathematical model of genes.)
I’m afraid you’re committing the much more common fallacy of assuming that humans (and possibly other species) know why they do a particular behaviour, and are actively trying to get their genes to the next generation.
But it’s not so.
You don’t need to know why you prefer humans of a particular gender and appearance any more than your leg needs to know why it kicks when a small force is applied below the knee cap.
Furthermore, humans have changed our environment much faster, for the most part, than evolution can keep up with.
The classic example is food preferences. In our natural environment, it made sense to eat as much as we could so that we didn’t starve at times when food was scarce. And sugary foods were almost always good for us – it wasn’t really possible to eat too much sugar – so sugar tastes good to us.
Fast forward to the modern world. Sadly, there is no meta-brain rewriting our instincts now that food is abundant. We have retained our instincts, and the result is obesity.
So in terms of attraction, yes, for the most part in humans we find things like good skin or defined abs indicators of health and fitness the same as any other species (that’s not to say that I agree with Trinopus that humans are evolving to become better looking).
My final line here could be taken as being inconsistent with what I was saying earlier. But I’m just using the same shorthand that many in the field do.
I’m not saying a given individual looks at boobs, say, and thinks “that’s an indicator of femininity and fertility”. It is an indicator and that’s why it’s been selected for, but the individual doesn’t need to know that.