Men tend to be in higher risk situations more often than women.

I thought it was because females have two copies of the X, so defects in a region of one copy can be compensated for by the other. RAID-1 ftw.

>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...