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Grandma Plays Favorites

from ScienceNOW Daily News

Most women have their last child before age 40. Why would Darwinian evolution favor such a cutoff, especially when most other mammals reproduce until they die?

A new study finds support for the "grandmother hypothesis," the idea that older women spread their genes most effectively by helping their daughters take care of their children.

In 1998, behavioral ecologist Kristen Hawkes of the University of Utah in Salt Lake City and her colleagues proposed that grandmothers lend their skill and experience to the rearing of their grandchildren. Hawkes and others cited the Hadza, a modern foraging society in Tanzania, in which grandmothers search for tubers while their daughters are breastfeeding their babies.