University of Utah Anthropology Professor Kristen Hawkes says humans are distinct among primates when it comes to longevity. “One of the things that’s really different about us humans, compared to our closest living relatives, the other great apes, is that we have these really long lifespans. We reach adulthood later and then we have much longer adult lives. And an especially important thing about that is that women usually live through the childbearing years and are healthy and productive well beyond,” she said.
Other primates are not as lucky. “In other great apes, females, if they make it to adulthood, they usually die in their childbearing years and they get to be old, frail and gray and less able to do all the things that we associate with getting old. Well, of course, it happens to all of us, but it happens slower and later to us compared to the other great apes,” she said.
Hawkes said climate change may have set things in motion by affecting food supplies. Savannahs started replacing forests in Africa. “One of the things it did was restrict the availability of the kinds of things that little kids, little apes, can feed themselves on. So that meant that ancestral moms had two choices. They could either follow the retreating forests, or if they stayed in those environments, then they just would have to feed their kids themselves. The kids couldn’t do it,” she said.
So, if mothers decided to feed their offspring themselves they would not be able to give birth as often. They’d just be too busy finding food. Here’s where granny primate steps in to help. She said, “It would also mean that older females, whose fertility was coming to an end, could now make a big difference in their fitness by helping their daughters feed those grandchildren. And that would mean that moms could wean earlier.” The act of early babysitting had long-range effects.
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