Genetic studies are revealing that men and women are more similar than distinct. So far, of the approximately 31,000 genes in the human genome, men and women differ only in the two sex chromosomes, X and Y, and only a few dozen genes seem to be involved. Moreover, it's now known that the Y has only about 30 genes and many of those are involved in basic housekeeping duties or in regulating sperm production. The X has hundreds of genes with a vast array of roles.
Strong evidence exists that these two chromosomes were once a matching pair of Xs, says Jennifer Graves, a genetics researcher at La Trobe University, in Australia. According to Graves, it's unclear why the male sex chromosome, the Y, shrunk and shed most of its genes over time. Humans are not alone in this. The Y chromosome's degeneration is well documented in fruit flies and ...
