Why Women Prefer Us. Ehem.

“It’s popular among male academics to say that females preferred smarter guys,” Dr. Arnold said. “Such genes will be quickly selected in males because new beneficial mutations will be quickly apparent.” Several profound consequences follow from the fact that men have only one copy of the many X-related brain genes and women two. One is that many neurological diseases are more common in men because women are unlikely to suffer mutations in both copies of a gene. Another is that men, as a group, “will have more variable brain phenotypes,” Dr. Arnold writes, because women’s second copy of every gene dampens the effects of mutations that arise in the other. Greater male variance means that although average IQ is identical in men and women, there are fewer average men and more at both extremes. Women’s care in selecting mates, combined with the fast selection made possible by men’s lack of backup copies of X-related genes, may have driven the divergence between male and female brains. The same factors could explain, some researchers believe, why the human brain has tripled in volume over just the last 2.5 million years.

If you can't understand this (read the whole thing in NYT), you are in the other extreme.