While women with curvy figures might enjoy more attention from men in Western culture, and find it easier to become pregnant, new research suggests they may also face some evolutionary disadvantages compared to women with thicker waists.
That’s because the same hormones that increase fat around the waist can also make women stronger, more assertive, and more resistant to stress, according to a new study published in the December issue of Current Anthropology.
Given those findings, it makes sense that the slim-waisted body has not evolved to become the universal norm, said the study’s author, Elizabeth Cashdan, an anthropologist at the University of Utah.
Her study takes aim at a theory popular in evolutionary psychology and medicine: that men universally prefer women with narrow waists and larger hips because their higher levels of estrogen make them more likely to conceive a child, and less vulnerable to chronic diseases. These preferences, the theory goes, have defined women’s ideal body shape over time.
One of the most tiresome aspects of evolutionary psychology is the paradigmatic straitjacket which many of the practitioners operate under; the only type of evolution that exists is unidirectional. Deviations from expectation are explained away. The importance of human universals mean that variation can not exist. These sorts of evolutionary psychologists resemble the caricature of the economist who holds to rational choice so that behavior which deviates from the model is explained by ad hoc contingencies. The most popular current expositor of this view of evolutionary psychology is Satoshi Kanazawa, who is also not a big fan of statistics. In any case, the paper will come out in Current Anthropology, but isn’t on the website, but there is a press release:
Androgens, a class of hormones that includes testosterone, increase waist-to-hip ratios in women by increasing visceral fat, which is carried around the waist. But on the upside, increased androgen levels are also associated with increased strength, stamina, and competitiveness. Cortisol, a hormone that helps the body deal with stressful situations, also increases fat carried around the waist.
“The hormonal profile associated with high WHR (waist-to-hip ratio) … may favor success in resource competition, particularly under stressful circumstances,” writes Cashdan. “The androgenic effects–stamina, initiative, risk-proneness, assertiveness, dominance–should be particularly useful where a woman must depend on her own resources to support herself and her family.”
In other words, trading the benefits of a thin waist for better ability to collect resources may be a good deal in certain societies and situations. And there is evidence that male mate preferences may reflect this trade-off, according to Cashdan.
In Japan, Greece and Portugal, where women tend to be less economically independent, men place a higher value on a thin waist than men in Britain or Denmark, where there tends to be more sexual equality. And in some non-Western societies where food is scarce and women bear the responsibility for finding it, men actually prefer larger waist-to-hip ratios.
In Demonic Males Richard Wrangham reports that orangutan males come in two morphs. A very large one, and a small one which seems to be a case of paedomorphism. Female orangutans prefer the normal large male orangutans as sexual partners. But the small ones do reproduce. How so? They ambush and chase the females and rape them. This is a behavioral strategy which can work well if the small variant morph is not extant as too high a frequency, because females will then not be “on alert.” How these sorts of variations emerge is clear to anyone who is cursorily familiar with evolutionary game theory.
I use the orangutan “raper” strategy as an example for a reason: some of the press will no doubt spin the new research as a victory for feminism and a rebuke to heteronormative males or something of that sort, at least implicitly. But the intersection of biology and behavior is fundamentally value neutral; humans are the ones interjecting norms. The old paradigm of evolutionary psychology, which I must admit is “Just So” and rooted in a coarse and outdated understanding of biological science, should be rejected on scientific grounds. Not only are there many areas where it offers little insight, but it is no longer compelling on theoretical grounds.
There are certainly a core of human behavioral traits which exhibit little variance, and are extremely constrained by purifying selection which fixes the trait so that only one morph is extant at appreciable frequencies. But there are many which no doubt exhibit continuities, while a fair number likely can be modeled as discrete strategies across the adaptive landscape, buffeted by stochastic & frequency dependent dynamics as well as exogenous parameters. As simple as sufficient, but as complex as necessary, should be the maxim.