Overall, women live longer than men, by at least five years. The differences in longevity rise dramatically as age increases. A whopping 85 percent of folks more than 100 years old are women [source: Blue].
Aging is, fundamentally, poor cell maintenance. Over time, cells become damaged; a poor or neglected repair job contributes to aging. Evidence suggests that, in an evolutionary sense, it's vital for women as child bearers and nurturers to remain healthy, so their bodies accommodate this. Once men have reproduced, individual health is less important for species survival.
The longevity of mothers is seen in other primates, as long as the mother is the primary caregiver. However, if both parents share responsibility (as in titi monkeys and siamang apes) their life spans are comparable. In the case of owl monkeys, fathers are rewarded with longer life, possibly because the dads have the burden of childcare (the mothers only nurse) [source: Barber].
Survival of the species is paramount over time, but there are other factors that contribute to gender variations in life expectancy. High testosterone levels that increase chances of fatherhood are detrimental to health in the long run. Testosterone can contribute to aggressive behavior in men. They are more likely to take risks resulting in violence and accidents. Women are less likely to take chances, especially if they have children.
There used to be a medical consensus that estrogen contributed to women's longevity. Not only has that been disproved, but estrogen supplements may be detrimental to post-menopausal women.
If estrogen doesn't play a role in the man/woman life expectancy disparity, iron (or lack thereof) might. Men have relatively higher levels of iron due to women's menses. Iron is instrumental during the creation of free radicals, which cause cell damage.
Meanwhile, behavioral aspects, perhaps related to testosterone, can also affect life span. Among depressed individuals, men are more likely to attempt, and succeed at, suicide. The grim success rate may be due to men's chosen methods, which tend to be more brutal and immediate -- gunshots and hangings are common.
It appears that a combination of environmental influences and underlying genetic differences account for the differences in life span between women and men. Perhaps safer behavioral choices (such as being wary of the dangerous pull of testosterone) can help men close the gap.
In industrialized countries, women live about 5 to 10 years longer than men do, and scientists are trying to figure out why. One reason may be simple: men tend to take more risks than women, from driving more recklessly to using drugs and alcohol. There may be some chromosomal factors involved. And according to one theory, women may have menstruation to thank for their long lives. Women experience a later onset of cardiovascular disease than men do, and that might be because they excrete excess iron during menstruation. Men are stuck with that iron in their bloodstreams, and iron can damage cells and cause free radicals to form, leading to cardiovascular conditions such as heart disease or stroke.
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