Via PhysOrg.com, more on possible biomechanisms for gender differences in longevity: "While both parents contribute to their offspring's cellular genetic inheritance, only the female passes on the mitochondrial genome to the next generation. Why, and how, this asymmetrical inheritance happens is not clear, but Tower thinks understanding it may be key to understanding sex differences in aging. ... Mitochondria play a key role in regulating the programmed cell death pathway, or apoptosis. In flies and humans, apoptosis works during normal embryonic development and sexual differentiation, sculpting the body by killing unwanted cells. But the cell death pathway, in which the p53 gene is a central player, also appears to malfunction more frequently over an organism's lifetime, thereby contributing to aging and aging-related diseases like Parkinson's. This might happen more often or differently in males, Tower speculates, leading to a shorter life span. Tower's far-reaching model leads to 'a list of predictions,' which his lab has already started testing in experiments with Drosophila. One that he's particularly interested in following up on is the idea that the human Xist gene may control sex determination and be very much involved in regulating human life span."