Glimmerings

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March 13, 2004

Being a grandmother is good for your health

Women with grandmothers nearby tend to have children sooner and more often than they would otherwise.

Nor was the increase due to a single effect. Instead, Dr Lahdenpera was able to disentangle a range of beneficial phenomena which, when added together, resulted in the increased reproductive success that she observed. People whose mothers were still alive both gave birth to more offspring and raised a higher proportion of those offspring to adulthood. They also gave birth to their first children at a younger age than those whose mothers had died, and the births of their children were more closely spaced. All of these things contribute to reproductive output.

Moreover, the physical presence of the matriarch was vital. Children who lived more than 20km from their mothers produced significantly fewer offspring than those who lived in the same village. That suggests the increase in the number of grandchildren was due not to some subtle genetic effect, but rather to help--whether physical or in the form of advice--that matriarchs were contributing.

Perhaps the most evolutionarily significant finding, though, is the age at which the matriarchs in the study died. The average lifespan of post-menopausal Finns was 68. Of Canadians, it was 74. These ages correspond to the points where the matriarch's children themselves had stopped reproducing. At that point, a woman's fitness plummets. And so, sadly, does her life expectancy.

Economist.com | Why women live so long

Posted by thdyck on March 13, 2004

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