Mars and Venus may be neither here nor there, but in the debate over whether male and female minds are different by nature, the two camps certainly seem to be on different cognitive planets. To one side, it appears obvious that men's minds are as much different from women's as their bodies are different from women's, and that this is evident from a range of qualities, from temperament to the ability to rotate objects in the mind's eye. To the other, any innate differences are marginal quirks, with negligible power to explain male dominance in the boardroom or laboratory.
Ben Barres, a Stanford University neurobiologist, passionately expounded the latter view in a recent article in Nature, continuing the controversy provoked last year when Larry Summers, then president of Harvard University, suggested that "intrinsic aptitude" might explain male predominance at the upper levels of science. Barres dealt with the data in one paragraph, finding little evidence of sex differences in mathematical ability, and devoted most of his essay to discrimination. In a sidebar, however, he affirmed, as a transgendered person (formerly Barbara Barres), that "no one understands more deeply than I do that there are innate differences between men and women". He noted that he still gets lost, but is no longer willing to ask for directions.
Undecided parties may feel rather similarly. But instead of trying to resolve the arguments over the evidence, we could usefully ask why male minds should differ from female minds anyway. The answer is that asymmetry is the basis of sex - eggs are large, sperm are small - and the interests of the sexes are asymmetrical. One sex is likely to invest more resources and care in its offspring; that sex is likely to be the more discriminating in its choice of mates. Among certain pipefish (these are straightened-out sea horses), males carry fertilised eggs in pouches and females compete to secure harems. Among mammals, however, it is always females that invest more.
This is a principle endorsed on both sides. In the words of the late Stephen Jay Gould, it "makes Darwinian sense and probably does underlie some different, and broadly general, emotional propensities of human males and females". Coming as it did in a polemic against evolutionary psychology, Gould's affirmation was rather like a comment in a neoconservative tract to the effect that "the history of all hitherto existing society is probably the history of class struggle".
Still, the idea remains honoured more in principle than in application. Those who doubt innate sex differences overlook it, and innatists fail to apply the logic of asymmetrical interests when they regard unequal outcomes with equanimity. If positions of power are filled by members of one sex, they will tend to use that power in their own interests, which will differ systematically from those of the other sex. Arguments from evolution can be used to expose discrimination as well as to deny it.