A new study indicates that testosterone could well be the culprit in men’s shorter average lifespans. Not sure what he’s talking about in regard to reproduction, though. AFP takes up the story:

The study, published in the scientific journal, Current Biology, used detailed genealogical records of the Imperial nobility during Korea’s Joseon dynasty, which spanned more than 500 years from the late 1300s to the early 1900s.
According to the data, most men, including kings and royal family members, died in their late 40s or early 50s. But noble-class eunuchs – men who were castrated either by accident or because of social benefits – lived, on average, to the ripe, old age of 70.
Study author Kyung-Jin Min of South Korea’s Inha University, said the reason is probably that manly hormone, testosterone:
“Testosterone is known to increase the incidence of coronary heart disease and reduce immune function in males,” he said.
…Castration “removes the source of male sex hormones”, the study notes, adding the practice has already been proven to help many male animals live longer.Castration also cuts off the possibility of reproduction, which Kyung-Jin noted could also be a factor.
According to “one of the leading theories of ageing, ageing occurs at the expense of reproduction”, he said, because the body has limited energy that can be used either to keep up reproductive function, or else to keep up everything else.