The Y chromosome is often considered somewhat of a genetic oddball. Short and stubby, it carries hardly any genes, most of which are related to traits associated with maleness. Most of the chromosome consists of highly repetitive sequences of DNA, known as massive palindrome sequences, whose function is unknown. Evolutionary biologists have long believed that the mammalian Y chromosome is essentially stagnant, having lost most of its genes hundreds of millions of years ago. But new research from MIT’s Whitehead Institute, published in this week’s issue of Nature, overturns that theory. The research team, led by Whitehead Institute director and MIT biology professor David Page, showed that the Y chromosome is actually evolving rapidly and continuously remaking itself.