Last January Harvard University president Lawrence Summers hypothesized that women may be innately less scientifically inclined than men. Not long after the ensuing uproar, researchers announced the sequencing of the human X chromosome. The project was hailed as a great leap forward in decoding the differences between men and women, at least from a biological perspective. While it did nothing to calm the maelstrom swirling around Summers, the new understanding of the chromosome revealed tantalizing clues to the role genes might play in shaping cognitive differences between the sexes. And while these differences seem to be largely to the female's advantage, permutations during the genetic recombination of the X chromosome may confer to a few men a substantial intellectual edge.
Considerations of this sort are mired in politics and sensationalism, but one fact is beyond dispute: Three hundred million years after parting ways in our earliest mammalian ancestors, the X and the Y chromosomes are very different genetic entities. The Y has been whittled down to genes governing a handful of functions, most entailing sperm production and other male-defining features. Meanwhile, the gene-rich X is the most intensely studied of the 23 chromosomes, largely because of its role in rendering men vulnerable to an estimated 300 genetic diseases and disorders associated with those mutations—from color blindness to muscular dystrophy to more than 200 brain disorders.
