The study, published in the Aug. 29 issue of PLoS ONE, notes that while women often lose their reproductive capacity around age 50, men can often remain productive into their 70s. From an evolutionary perspective, women who can no longer reproduce are non-players, and since "it takes two," men partnered with menopausal women are also irrelevant.

More interesting, when old men father children, their genes seem to increase the lifespan of both sexes over evolutionary time.

Thus, Charles Darwin would say it's advantageous for males to live longer lives providing they can find a woman capable of reproducing. Natural selection should favor longevity-boosting genes, which would get passed down from fathers to both sons and daughters. So women would benefit as well in future generations, the scientists say.

"By increasing the survival of men you have a spillover effect on women because men pass their genes to children of both sexes," said study team member Cedric Puleston, a doctoral candidate at Stanford University.