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  3. To understand better the forces that control human aging and longevity, we have tried to determine whether the longer lifespan o

To understand better the forces that control human aging and longevity, we have tried to determine whether the longer lifespan o

admin2011-04-26  51
问题     To understand better the forces that control human aging and longevity, we have tried to determine whether the longer lifespan of females might be part of some grand Darwinian scheme. Gender differences in longevity have been【51】in other members of the animal kingdom: in fact, in almost all species that have been observed in the wild, females【52】to live longer than males. Female macaques live an【53】of eight years longer than males, for example, and female sperm whales outlive their male【54】by an average of 30 years.
    It seems that a species’ lifespan is roughly correlated【55】the length of time that its young remain【56】on adults. We have come to believe that【57】a significant, long-term investment of energy is required to ensure the survival of offspring, evolution favors longevity—in【58】, female longevity. Indeed, we believe that the necessity for female【59】in the human reproductive cycle has【60】the length of the human lifespan.
    We start with the assumption【61】the longer a woman lives and the more slowly she ages, the【62】offspring she can produce and rear to adulthood. Long-lived women【63】have a selective advantage over women who die young. Long-lived men would【64】have an evolutionary advantage over their shorter-lived【65】.But primary studies suggest that men’s (66)  capacity is actually limited more by their access【67】females than by lifespan. Hence, the advantage of longevity for men would【68】be nearly as significant as it is for women. And because males historically are not as【69】in child care as females, in the not so distant evolutionary past the survival of a man’s offspring depended not so【70】on how long he lived as on how long the children’s mother lived.
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