The Importance of Grandmothers

"By living longer and having more offspring," said Rachael Caspari, a research scientist at the University of Michigan." Older people allow more information to accumulate and transfer between generations, as grandparents survive to educate and contribute to extended families."

Caspari's result derives from a series studies on Homo sapiens, namely early human beings.

By analyzing a large number of sample Neanderthal teeth and fossils, Caspari and her colleagues found that none of the Neanderthals lived beyond 35, and have a very low older-to-younger adult ratio.

In contrast, she found in another study that the early Upper Paleolithic, another species of Old Stone Age sapiens which have an extended average life cycle of 50 years old.

"The fact that significant numbers of grandparents first survived played an evolutionarily significant role in the Upper Paleolithic," she said. "The role of grandmothers was likely less important for Neanderthals."

"The role of older women is extremely valuable because of their productivity," said Caspari. "This is what you call the 'grandmother effect.'"