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Desert Diary


Most of us have fond feelings for grandmothers, whether ours or not. This appears equally true whether we're talking of the peoples of our Chihuahuan Desert or of those in farthest Mongolia. Now it turns out that this is not just happenstance of human sociality, but is recognized and set by the blind rules of natural selection. One of the biological mysteries about humans has always been the question as to why women live so long beyond the age of bearing children. This is not a feature of even our closest relatives. Nevertheless, usually a third or more of the women in a population, whether of primitive hunter/gatherers or of our recent historical past, are beyond the age of 45.

Now, one suggested reason is backed up by evidence that shows that families with such surviving women are more successful in raising grandchildren. Unlike our close relatives, a child after weaning is still dependent upon adults—and who is more adult than good old grandmother? Being a grandmom is a good way to insure your genetics are passed on!
pen and ink

Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.


Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.



Hawkes, K. 2004. The grandmother effect. Nature, 428:128-129.

Lahdenpera, M, V. Lummaa, S. Helle, M. Tremblay, and A. F. Russell. 2004. Fitness benefits of prolonged post-reproductive lifespan in women. Nature, 428:178-181.


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