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Evolution Without grandmas, there would be no longer couple relationships
According to researchers, grandmothers are very important in the evolution of living together. The supply of the children by grandmothers therefore not only extended the life expectancy, but also promoted the monogamous twin relationships between men and women.
More and more capable men
"Grandma is the best": This saying was apparently in most cultures thousands of years ago. According to a news agency dpa news agency, researchers now report in the Proceedings of the US Academy of Sciences (PNAS) that grandmothers may have played a crucial role in keeping humans in perennial relationships, as is the case today. As the US anthropologist Kristen Hawkes of the University of Utah in Salt Lake City, who was also involved in the current study, reported many years ago together with colleagues, grandmothers extend the children's lives through their care.
Evolutionary research: The grandma is forging partnerships. Picture: drubig-photo - fotolia At that time, the scientists calculated that life expectancy rose from an average of 25 years to 49 years after 24,000 to 60,000 years, thanks to grandmother support. Due to the increased average life expectancy of humans, according to the current study, more and more able-bodied men accounted for the women of fertile age. As a result, a strong pair bond gave the men significantly higher prospects for many offspring as changing "one-night stands".
"Too many other types than competitors"
"It seems the grandmother's commitment has been crucial in making the bond," Hawkes said. Together with statisticians and mathematicians, the researcher had simulated the development of a community with and without the intervention of grandparents. It showed that fertile men in more durable communities over time - even in old age - competed for the significantly smaller number of women of childbearing potential. As the simulations showed, the male surplus increased from 77 to 156 men per 100 women over 30,000 to 300,000 years through the "grandmother effect". "This male gender bias made partnering for men a better strategy than finding extra partners - there were just too many other types than competitors," Hawkes said.
Supporting grandmas increased chances of survival
However, other anthropologists represent the so-called "hunter thesis": Thus, the pair bond developed mainly because hunting men could reliably provide the wife and common offspring. Hawkes sees it differently: "The key to moms getting more babies faster is not Daddy, who brings the ham home, but grandma who helps feed the weaned children."
With the new analysis, she protects her grandmother's hypothesis, which has been discussed for years, which explains why women live so long after the end of their fertile period - which from a biological point of view makes no sense at first. The support of the grandmothers was therefore immensely important in the care of small children and increased their chances of survival massively. As a result, during evolution, the genes of families in which the grandmothers lived very long lived through.
The longer grandmas live, the more they help
The scientists around Hawkes had developed their theses after field research almost 20 years ago among the people of Hazda in northern Tanzania. The grandmothers actively helped Hazda, a hunter-gatherer, feed the already undressed infants with dug-up roots and tubers. The children were still too small to dig for food themselves, and their mothers often had a new baby on their breasts. In 2012, Hawkes then compared in a further study with scientists from the School of Mathematics and Statistics at the University of Sydney (Australia) in extrapolations the granddam effect of the Hazdas with the lifetimes of great apes.
The effect became apparent even when calculating brain size or hunting behavior: if the grandmothers are not an important help, the female members of the group usually die a few years after the end of their reproductive ability. The human lifespan lengthened - as mentioned above - in the course of 24,000 to 60,000 immense. "Longer-lived grandmothers help more," says the researcher. So far, scientists have not found a grandfather effect. (Ad)