Paleoanthropologist John Hawks passes along a debunking of the recent article in the UK Times, “Women are getting more beautiful“ written by the author of the study allegedly claiming that “beautiful” women have higher reproductive success. You can read more about the author’s discontent at Hawks’ blog but I’d like to call out this tidbit Hawks found interesting
One interesting thing [from the author]:
So how much is 0.02 standard deviations? Perhaps it helps to consider the effect magnitude in another context: if natural selection were to favor tallness with the same strength as observed for attractiveness here, height would increase by ~0.20cm (or 0.08 inches) per one generation. Such a slow process would be observed only over several generations, say, at least 5-10 generations to get an observable effect. In other words, the finding says nothing of comparison of people’s attractiveness in the 1950s vs. the 1970s vs. the 2000s!
The media always want to put things in the terms of the last and next generations. That’s understandable — most of their readers couldn’t care less about people 100 years ago, much less 1000 years ago. But in this case, although Jokela says the selection is “weak”, it would actually be pretty strong in evolutionary terms. He’s talking about a 16 percent reproductive advantage for women in the second-highest “attractiveness” quartile. One standard deviation in 50 generations (or two in 100 generations) would be abrupt change.
Human craniofacial phenotypes have been changing, but across the last few thousand years I wouldn’t say it’s been as fast as two standard deviations per 100 generations. So that raises an obvious question: Why are things different today? And if we like to mate with the beautiful so much, why is “attractiveness” still heritable?
Recent differential reductions in fertility in the sampled population, changes in other social correlates of mating success (like physical labor, or family wealth), alterations or oscillations in judgements about attractiveness, unobserved epistatic associations with attractiveness, social effects of media stereotypes — there are a dozen or more obvious hypotheses. Don’t start counting your future Eloi chickens before they’ve hatched.
I’m not positive Hawks or the original author would agree (although see that last paragraph) but another thing you can draw from a 0.02 standard deviation is that considering all other possible factors that’s awfully close to random noise. And there’s really no reason to imagine that a straight-up preference for “beauty” in women (however great or small that preference might be) has changed that much in the last 2,000… or 10,000 years. Let alone actual “beauty.” Especially since definitions of beauty tend to vary considerably from culture to culture and even generation to generation within cultures. (Or, for that matter, different ages within the same culture and generation!)
Note: Assuming a new generation every twenty years for humans there haven’t been many more than 500 generations since people first started building cities in the fertile crescent.
Submitted by 3105 (not verified) on Tue, 2009-08-04 21:30.
There are some standards of beauty that are fairly universal, however. One is perfect symmetry. Two is proportionally and positionally average features, especially facial features. Three, there are a number of average preferences (such as hip/waist ratio among women, for men) that probably don't change that much despite fashion trends - just because it's "fashionable" or even socially pressured to express a preference for something doesn't mean that the actual preferences change that much for some things. (Admittedly, #3 might be wrong and is probably a much weaker factor than #1 and 2 even if it's correct, but it had to be said anyway.)
So it could be happening. However, if it is, it's probably very very slow, because in the past long-term survival abilities were a far more important factor in human evolution than "beauty", and in modern times there's plastic surgery for the wealthy, who tend to be the ones more concerned with beauty anyway. And if it's not, people might simply be becoming more attractive in modern times merely due to better nutrition.
Besides, it's really hard to come up with proof one way or another. Photography didn't exist for most of history, other forms of art tended to be idealized rather than realistic, and skull-based reconstructions would only be completely reliable if ancient peoples had modern genetics (which wouldn't prove anything useful in this regards if they did) and access to modern health and nutrition (which they didn't).
[Not to mention that the data the researchers used -- photos of women in high-school yearbooks from mid-20th-Century Wisconsin -- would have been distorted by a) makeup and hair-styling and b) literal airbrushing of photos, a common practice in the pre-digital commercial portrait-photography industry. "More makeup" could be an indicator of "more affluent," or even "more heterosexual and thus more likely to marry and have children in the first place." Again, it's not that symmetry and ratios don't show up in standards, it's just that the data used to indicate "beauty" would have had to be mostly about faces. Photos of faces at that. Made up, possibly airbrushed photos of faces. And so that might not have been the very best place to go looking for data -- just the only easily available and somewhat standardized source. Which isn't the same thing. At all. Thanks, Nightfall. --fl]