Women's Longer Lifespans Explained: Men Are 'Genetically Disposable'

(Nov. 1) -- Women can credit their longer lifespans to genetic resiliency, says a new study that deems men to be "genetically more disposable" than the fairer sex.

Us ladies tend to live five or six years longer than our male peers. In the United States, that means a woman's life expectancy is around 80 years, while that of a man is closer to 75. But surprisingly, the divergence between men's and women's relative life expectancy actually holds true in myriad locales around the world -- industrialized or not.

Why? Experts still aren't sure, but an idea dubbed "disposable soma theory" is picking up steam, with newly published research adding more evidence to the concept.

Professor Thomas Kirkwood first established the theory in the 1970s, based on the idea that aging and death are largely products of gradual cell damage and disrepair.

Evolutionarily speaking, an organism's primary role is to pass genes on to the next generation. So it follows that the human body's repair mechanisms slow down and become less effective as we reach old -- i.e., nonreproductive -- age.

But in a new paper published in Scientific American, Kirkwood hypothesizes that women's cell repair mechanisms are more resilient than those of men.

"Under the pressure of natural selection to make the best use of scarce energy supplies, our species gave higher priority to growing and reproducing than to living forever," Kirkwood writes.

Studies on mice reinforce the idea. For example, female mice can repair cellular damage more effectively than males -- at least until their ovaries are removed.

Kirkwood notes that it is "difficult to say things with absolute assurance," but his idea is a natural fit where evolution is concerned. Females not only rear offspring, but also nurture them into adulthood. Males, in contrast, are little more than reproductive partners.


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