The bubbe hypothesis

How grandmothers helped humans evolve

Grandmothers: they feed you, they spoil you, they constantly needle you about your relationship status.

And, according to anthropologist Kristen Hawkes, they might be the driving force behind the evolution of much of human society.

Hawkes, an expert in human evolu- tion and sociobiology at the University of Utah, is the author of several studies on the “grandmother hypothesis,” which asserts that many of the characteristics that distinguish us from our ape ancestors are thanks to the thoughtful care of our mothers’ mothers.

In the latest, published last week in the Proceedings of the National Academy of Sciences, she and her co-authors explain how grandmothering is a crucial factor behind the spread of monogamy.

The ancient evolutionary explanation goes like this: when grandmothers started to help out with childrearing, they freed up mothers to have more children, more quickly. Those longer-lived grandmothers ended up having more grandchildren, each of whom carried their genes for longevity, helping to increase the human lifespan. Longer lives and larger kin networks also made it more advantageous for men to mate with and protect a single women, so humans relationships became monogamous.

No wonder Grandma is always asking why you aren’t married yet.

The presence of post-reproductive women is something of an anomaly in the natural world, where the prime directive is to find food and a mate. Among primates, humans are the only species that continue to live beyond menopause.

Since having children is what drives evolution, there’s no good evolutionary reason for women to live past their ability to reproduce — at least as far as nature is concerned.

Unless, as Hawkes suggests, it’s so those women can become grandmothers.