Women today behave very much more like men than their grandmothers. After all, they attend college to compete in careers (rather than to find a husband). They are interested in sex. They drink alcohol and do drugs. They are active in competitive sports, including as professionals.

Social scientists often attribute such profound changes to "sexual liberation" but this is really more of a semantic trick than a true scientific explanation. It is an exercise in circular reasoning. We should not be too surprised by that because virtually all so-called explanations in the social sciences follow a similar defective formula as I argue in scholarly detail in my recent book "The myth of culture: Why we need a genuine natural science of societies."

If women are behaving more like men and scholars attribute this to sexual liberation, we are entitled to be skeptical. It is tantamount to saying that women are now free to behave more like men because they are more free to behave like men (i.e., have been sexually liberated, or unshackled from feminine "roles"). We are in the presence of the Rumpelstiltskin effect - give the problem a name and it goes away.

It is all too easy to be a critic, of course. If one wanted to provide a real explanation for changing feminine behavior, what would this be? There are different possible levels of explanation but the most basic is biological. A lot of evidence is accumulating that the competitive behavior of men and women, just like that of other species is mediated by changing levels of sex hormones.

Using hormones as an explanation may seem far too simple, a case of biological reductionism run amuck. Ironically, hormonal explanations are never quite as simple as might be imagined for the simple reason that behavior affects hormones and hormones affect behavior in a never-ending chain of reciprocal causation. That is why hormones are such a valuable clue to understanding changes in gender-typed behavior.

This argument was advanced most explicitly by Anthropologist Elizabeth Cashdan of the University of Utah in a recent paper in Current Anthropology that is ostensibly concerned with changing female body shape. Cashdan believes that the optimal female body shape is not the hourglass figure of a Marilyn Munroe or a Scarlett Johansson with narrow waist and large breasts. In most societies, women actually have wider waists and such figures are more attractive to men in subsistence societies, such as the Zulu (pictured) where food is scarce and also in countries like Denmark and Britain where there is greater equality between men and women.

In societies where women are under pressure to provide for their children, increased testosterone production increases their stamina, strength, and competitiveness. However, along with stress hormones, testosterone also increases the amount of fat stored about the waist, thereby reducing stereotypical femininity of the figure.

Cashdan's results are mainly descriptive rather than statistical because she did not have a large enough number of societies to compare. My own statistical analyses of women's ideal figures as they vary from year to year in magazine pictures, also found that women subscribed to less curvy ideals when they entered higher education and careers in large numbers, see [amazon 1573929700]. When they compete with each other for jobs, they are more interested in seeming competent than in looking sexy. During the 1950's, when women briefly reverted to marriage, rather than careers, a sexier figure was preferred in ladies magazines. This was the heyday of Jane Russell and Marilyn Munroe.

A boost in testosterone production thus helps explain why women not only behave more like men but actually develop a more masculine body shape. All of these phenomena fit together in a neat pattern whereby women change in ways that help them to succeed in different kinds of societies. Such a neat match between body and behavior (or phenotype) and what is required for competitive success is really an adaptation.

Adaptations are often thought of as lock-and-key type relationships between the phenotype and the function. The giraffe's neck is an ideal "crane" for reaching into tall trees, for instance. If the social environment is the lock, and female competitiveness is the key, then hormones are the locksmith grinding out women to succeed in many different societies. Of course, men have also begun to behave more like women, adjusting to their greater role in caring for children thanks to other hormone locksmiths.

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