Grandmothers Responsible for Human Longevity
The helpfulness of grandmothers is the reason humans don’t die in their thirties the way chimpanzees do, new research shows – and may even explain our bigger brains. Computer simulations show that with only a little grandmotherly care, animals with chimpanzee lifespans evolve to reach a human level in less than 60,000 years.
“Grandmothering was the initial step toward making us who we are,” says Kristen Hawkes of the University of Utah. The simulated creatures were given an initial lifespan of 25 years from reaching adulthood. But after 24,000 to 60,000 years of grandmothers caring for grandchildren, the creatures reaching adulthood lived another 49 years, just like human hunter-gatherers. The long-standing ‘grandmother hypothesis’ says that when grandmothers help feed their grandchildren after weaning, their daughters can produce more children at shorter intervals. Thus, a few ancestral females who lived long enough to become grandmothers passed their longevity genes to more descendants.