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Grandmothers: Their childcare was crucial to evolution, says new study

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Ann Hermes / The Christian Science Monitor

(Read caption) Grandmothers were crucial to human evolution by increasing life spans through childcare, a new study shows. Here, Rita Cheong arrives to babysit her great-grandchild, Annika Liu, as the child's mother, Ingrid Ahlgren, leaves the apartment for work in New York, May 1, 2012.

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My mother is going to like this one.

Grandmothers, it turns out, are super duper important – not just in their own families, but for the human species overall.

A new study published today in the British biological journal “Proceedings of the Royal Society B”  gives new mathematical support for a long standing theory called the “grandmother hypothesis” – basically the idea that humans developed longer lifespans than apes because grandmas (or nanas, grammies, gogos, bubbas; take your pick) helped feed their grandchildren.

Test yourself: Are you a helicopter parent?

The theory goes basically like this:

Since grandma was keeping an eye out for the nutrition of Baby 1, mom could concentrate on making Baby 2. On average, then, women with able-bodied mothers had more kids, which meant that long-living grandmothers passed along their longevity genes to more descendants.

Voilà! Longer-living humans. (OK, a little more complicated than that, but you get the idea.)
This is important to remember when your mom inquires as to whether your baby is eating enough. She’s got the species in mind. Really.

Professors from the University of Utah and the University of California, Los Angeles first proposed the grandmother hypothesis in 1997, after they had lived with hunter-gatherer people in Tanzania and noticed that older women spent their days gathering food for their grandchildren. This was different than other mammals, they realized. They incorporated additional research, and came up with their theory.

But there has been a lot of debate about the grandmother hypothesis, in large part because it lacked a mathematical foundation.

And that’s just what the new study attempted to add.


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