>This unevenness hints that factors other than the presence of certain sex chromosomes might also strongly influence longevity, the team says. One of these factors could be sexual selection. Exaggerated physical traits and elaborate behaviors make males of some species more attractive to females but require large amounts of energy and take a toll on overall health.
Perhaps the riskiness of male behavior in humans is built in at the chromosonal level...
Basically, for whatever reason, a larger sex chromosome (X is much bigger than Y) confers a better chance of survival.