In my last post, I pointed out that testosterone fuels the reckless sexual and aggressive behavior of young men and other male vertebrates. Recent research is closing in on sex hormones (androgens as well as estrogens) playing a very similar role for women.

The female hormone estradiol (a key estrogen) plays a role in dominance communication and physical aggression among primates. Recent evidence suggests that it stokes competition amongst human females. Women with a high need for power have higher estradiol levels in their blood. What is more, their estradiol level increases when they "win" a contest with another woman that is actually manipulated by experimenters and remains elevated for a day. Estradiol declines when they lose.

So far, it seems that estradiol plays a similar role in the competitive interactions of women as testosterone plays for men. Yet, there is little evidence that high-estradiol women are more aggressive in the way that high-testosterone men tend to be. Their other distinguishing features are that they tend to be physically attractive, t