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.