Posted: Nov 8, 2012 10:23 PM by Xiaoyun Wu
Updated: Nov 13, 2012 7:51 PM
COLUMBIA - A new study supports a hypothesis that grandmother childcare makes an evolutionary contribution to human longevity. Local anthropologists express their own opinions regarding the "Grandmother Hypothesis."
Anthropologist Kristem Hawkes of the University of Utah led a study, which was published in the Proceedings of the Royal Society B. The study used computer simulations of chimpanzee, our closest evolutionary relative, to determine what factors impact life expectancy. The results show when grandmothers were involved, mothers were able to have more children and pass on their good long-life genes. This longevity gene passing could have extended the average life expectancy by 25 to 49 years over the past 24,000 to 60,000 years.
The study supports the "Grandmother Hypothesis," which has raised controversies over the years. It suggests that grandmothers' help is the dominant reason for human longevity. In this way, the daughter could have more children, and a female's post reproductive lifespan is reflected in the reproductive success of her offspring.
"I just think this will be easier for my daughter," said Linda Russell, grandmother of an 18 month old.
Russell had no idea of the evolutionary hypothesis, but she said her help was out of love, like most grandmothers do.
"I'd say I agree with the grandmother hypothesis," said Libby Cowgill. "What you can do as a grandmother to increase the number of offspring that your daughters have, and to increase the likelihood that those offsprings would survive to their daughter than they reproduce on their own, is going to be favored under natural selection."
Mary Shenk, of the MU Department of Anthropology, would like to expand the hypothesis. She said grandmothers are part of the reason, but not the entire explanation. "Grandmothers, men, brain revolutions, and cooperative breedings all play a part, but how much do these parts play a role? It still needs researching."
Missouri's average life expectancy is 77.44 years old, ranking 39th among all the states, according to the World Life Expectancy website.
"Looking at people in modern America and people in Missouri, I would say the real relevance is that it's still really difficult to raise a child by yourself in this age, so single mothers typically need a lot of help," Shenk said.