Photo: Flickr / lovefool416
A new study suggests that humans have a long lifespan, way past their fertile years in some cases, because being a grandmother is helpful.Other primates die relatively early in life — usually around the time they stop being fertile. In comparison, women continue living long after we’ve gone through menopause. The “grandmother hypothesis” suggests that this post-menopausal period is an evolutionary adaptation, that the childcare from grandmothers helped humans succeed.
The hypothesis, originally suggested in 1997 based off observations of hunter-gatherer tribes, has been controversial, and hasn’t had any mathematical evidence supporting it until now.
The new study, published in the journal Proceedings of the Royal Society B: Biological Sciences, used computer simulations to determine what factors influenced longevity. They started with lifespans similar to our closest evolutionary relative, the chimpanzee, and simulated the impact that grandmothers would have — helping find food and caring for children.
They found that when grandmothers were involved, their daughters were able to have more children, passing on their good long-life genes. In 24,000 to 60,000 years this longevity gene passing would extend our average lifespan from 25 years to 49 (the average life of a hunter gatherer).
“Grandmothering was the initial step towards making us who we are,” study researcher Kristen Hawkes of the University of Utah, told The Telegraph. It resulted in “a whole array of social capacities that are the foundation for the evolution of other distinctly human traits, including pair bonding, bigger brains, learning new skills and our tendency for co-operation.”
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