TO DIE young is the curse of being a man. Conventional wisdom has it that men have only themselves to blame: if only they spent less time trying to be like James Dean, they鈥檇 survive a little longer.
But while there is plenty of evidence that risk鈥搇aden, macho lifestyles do court disaster, studies on animals and people hint at another reason for the early demise of men. Parasites living on a range of animals seem to prefer whichever of the sexes is the larger, almost always the male.
Sarah Moore and Kenneth Wilson at the University of Stirling in Scotland analysed existing data on body size, lifespan and parasite infections for 355 mammal species. The pair found that whichever was the larger sex tended to suffer more heavily from parasites and to have a shorter lifespan (Science, vol 297, p 2015) even after other factors such as genetic similarities were ruled out.
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They speculate that larger animals present an easier target for parasites. Big creatures eat more and must forage more widely. This, combined with their size, makes them easier to latch onto.
Reviewing the findings in the same issue of Science, Ian Owens of Imperial College in London re-analysed data on human disease from the World 午夜福利1000集合 Organization to see if the parasite link held true in humans.
It did. On average, men in the US, Britain and Japan are twice as likely as women to die of a parasitic disease. In countries where parasites are more common, such as Kazakhstan and Azerbaijan, men were four times as vulnerable. 鈥淢ales are not special, they just tend to be big,鈥� says Owens.