Does Grandma play favorites?

On Science's online news service, ScienceNOW, I report on a very interesting paper from Leslie Knapp of the University of Cambridge and her colleagues that seems to provide additional support for the "grandmother hypothesis,"
the idea that the human menopause evolved because it allowed older women to help their daughters raise their own children.

Support for this notion of an evolutionary tradeoff between spreading one's own genes by having one's own children and doing so by helping grandchildren to survive has been inconsistent. The new study may show why: How strong the effect is depends on how closely related a grandmother is to her grandchildren.

Researchers seem surprised that this correlation is so strong, but the statistical significance is very high. Nobody is suggesting that grandmothers deliberately favor certain of their grandchildren, however, and the mechanism for this is still being worked out. The authors suggest a few possibilities, which I list at the end of my story.

Photo: A grandmother and child from Malawi/Rebecca Sear

Whatever happened to Kenyanthropus platyops? My latest post for Science's Origins blog may seem somewhat inside baseball, but I assure you it's an important issue for human evolution researchers.

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