There's been recent speculation that an increasing life span during human evolution may have been an important element in that evolution and the development of civilization. The idea is that people living beyond reproductive age do not become a burden to survival of the group; rather, an extended family allows the post-reproductive members to take over many of the chores of raising the older children and perhaps of food gathering. The result would be that mothers could spend more time nurturing their babies, increasing the survivability of the very young. Also, knowledge gained over many years could be passed along to younger adults.
Now, the fossil record is producing evidence compatible with this
scenario. Recently, researchers estimated the age distribution within populations over
several million years by studying wear on fossil wisdom teeth. They found that although
there was a small rate of increase in older people compared to young adults over the
millennia, the ratio jumped dramatically about 30,000 years ago. For the first time
ever, there were roughly two people of grandparent age for every young adult.
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.