There are a great many theories and associated studies relating to the well known difference in life expectancy between genders in our species:
Differing smoking rates, stem cell effectiveness, mitochondrial effectiveness, and the possible effects of hormones on the immune system are all on the list. [As well as the theory] that hormones influence the expression and activity of known longevity genes.
At the Longevity Meme, I recently pointed out a paper suggesting that men age faster for evolutionary reasons. Today I'll direct your attention to another evolutionary examination, via In Search of Enlightenment, where links are provided to the PDF format paper and related press release:
Researchers have long known that women outlive men on average, and more recently have discovered that men have higher mortality risks across the entire lifespan. University of Michigan researcher Daniel Kruger offers this explanation: It is all about sex. Women invest more physiologically in reproduction than men, thus men compete with other men for mating partners and try to make themselves attractive to women. This competition leads to strategies that are riskier for men both behaviorally and physiologically, and these result in higher levels of mortality.
This study examines three socio-demographic factors related to variation in human male reproductive success; polygyny, economic inequality, and the population ratio of reproductively viable men to women across nations with available data. The degrees of economic inequality and polygyny explained unique portions in the sex difference in mortality rates, these predictors accounted for 53% of the variance.
This is interesting, but is it at all important? Probably not, as is the case for much of the study of the area in which metabolism, aging, and longevity overlap. There is no such thing as useless information in the life sciences, but this sort of research will have most likely have limited utility when it comes to greatly extending the healthy human life span. Fully understanding and reengineering metabolism isn't as important to progress as learning to repair the metabolism we have.