From Science Daily:
It turns out that older men chasing younger women contributes to human longevity and the survival of the species, according to new findings by researchers at Stanford and the University of California-Santa Barbara.Read it here.
Scientists have long been puzzled by the fact that humans live long beyond their reproductive years while most other species die off. Until recently the dominant theory was the "grandmother hypothesis" holding that old women were necessary to assist mothers with child rearing. Therefore having old people around conferred some evolutionary advantage. That hypothesis was never confirmed, but it has now been replaced by another one that has been confirmed by mathematical models [hey, it works for environmental science, why not here?].
When old men mate with young women they pass along to their offspring genes that promote longevity. Over time these genes accumulate in the population and human lifespan increases. It only works for old men and young women; women past their child-bearing years cannot pass on their genetic advantage.
So, all you hot young chicks, if you really want to do something for the benefit of humanity, find an old man [the older the better] and make him really, really happy.