New York: If you have finally discovered who is going to be your life partner, do not just thank your stars but all grandmothers since human evolved as the act of “grandmothering” has helped us bond well throughout the history, interesting research has shown.
According to anthropologist Kristen Hawkes from University of Utah, it looks like grandmothering was crucial to the development of pair bonds in humans.
Pair bonds are universal in human societies and distinguish us from our closest living relatives. “Our hypothesis is that human pair bonds evolved with increasing payoffs for mate guarding, which resulted from the evolution of our grandmothering life history,” Hawkes proposed.
The famed "grandmother hypothesis” credits pre-historic grandmothering for our long human lifespan.
Hawkes used computer simulations to link grandmothering and longevity to a surplus of older fertile men and, in turn, to the male tendency to guard a female mate from the competition and form a “pair bond” with her instead of mating with numerous partners.
The findings contradict the traditional view that pair bonding resulted from male hunters feeding females and their offspring in exchange for paternity of those kids so the males have descendants and pass on genes.
For the study, the researchers ran computer simulations of human evolution - 30 simulations with grandmothering and 30 without.
The new study indicates the ratio of fertile men to fertile women increased over time.
“That's what made it advantageous for males to guard a female and to develop a pair bond with her,” Hawkes said.
The grandma hypothesis holds that "the key to why moms can have next babies sooner is not because of dad bringing home the bacon but because of grandma helping feed the weaned children”.
“That favoured increased longevity as longer-lived grandmothers helped more,” Hawkes noted.
The new study focused on the resulting excess of older males competing for mates, a likely source of men's preference for young women.
“This is different than what you see in chimpanzees, where males prefer older females,” added Hawkes, distinguished professor of anthropology and National Academy of Sciences member.
As human longevity increased, there were "lots more old guys, so you have an increasing number of males in the paternity competition, and the only way you can become a father is with a fertile female, which means younger females”.
“So males who had preference for younger females were more likely to leave descendants,” she pointed out.
The shift to grandmothering was the foundation for several important steps in human evolution, including longer adult life spans, increased brain size, empathy, cooperation and pair bonding, the authors noted.
The study appeared in the journal Proceedings of the National Academy of Sciences.