ANIMALS at high risk of violent death grow old faster than those whose lives are less precarious, says an American evolutionary ecologist who has compared mortality rates and ageing across many species of birds and mammals. The study confirms biologists' suspicions that evolution routinely tinkers with the rate at which animals age, and also suggests that some species have stretched their lifespans very near to an upper biological limit.
Researchers who study ageing view the process as an inevitable consequence of evolution. Because animals die from many causes besides old agepredators, starvation, drought and cold weather, for examplethe number of survivors goes down with passing years until eventually so few old individuals exist that they become evolutionarily irrelevant.
As a result, natural selection will be unlikely to weed out genes with harmful effects at this late age, especially if they are beneficial earlier in life. Similarly, selection should favour cellular ...
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