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Evolutionarily speaking, we are born to make babies. Our bodies—and brains—don’t fall apart until we come to the end of our child-bearing years. So why are grandmothers, who don’t reproduce and who contribute little to food production, still around and still mentally sound? A new study offers an intriguing genetic explanation.
Scientists have proposed several explanations for why our species lives as long and as healthily as it does. One idea is that grandmothers help out with child rearing. A 1998 study found, for example, that a Hadza group of hunter-gatherers in Tanzania had more babies if grandmothers helped feed their newly-weaned young grandchildren. The researchers speculated this kind of care freed up young mothers to reproduce, and ensured that the caregiver grandmother’s genes were passed on to more young. They called their theory the “grandmother hypothesis.”
But grandmothers need to have all their wits about them to help out in this way, and the new study may explain how this happens. Physician-scientist Ajit Varki and evolutionary biologist Pascal Gagneux of the University of California, San Diego, arrived at the findings accidentally. The pair was studying a gene that helps control the body’s inflammatory and immune response to injury or infection. Previous studies have linked two forms of the gene—CD33—to Alzheimer’s disease. While one CD33 variant, or allele, predisposes a person to the disease, the other appears to protect against it by preventing the formation of protein clumps in the brain.
Read full, original post: Anti-Alzheimer’s gene may have led to the rise of grandparents