Category Archives: Transhuman News

ScienceDaily (Oct. 23, 2012) Computer simulations provide new mathematical support for the "grandmother hypothesis" -- a famous theory that humans evolved longer adult lifespans than apes because grandmothers helped feed their grandchildren.

"Grandmothering was the initial step toward making us who we are," says Kristen Hawkes, a distinguished professor of anthropology at the University of Utah and senior author of the new study published Oct. 24 by the British journal Proceedings of the Royal Society B.

The simulations indicate that with only a little bit of grandmothering -- and without any assumptions about human brain size -- animals with chimpanzee lifespans evolve in less than 60,000 years so they have a human lifespan. Female chimps rarely live past child-bearing years, usually into their 30s and sometimes their 40s. Human females often live decades past their child-bearing years.

The findings showed that from the time adulthood is reached, the simulated creatures lived another 25 years like chimps, yet after 24,000 to 60,000 years of grandmothers caring for grandchildren, the creatures who reached adulthood lived another 49 years -- as do human hunter-gatherers.

The grandmother hypothesis says that when grandmothers help feed their grandchildren after weaning, their daughters can produce more children at shorter intervals; the children become younger at weaning but older when they first can feed themselves and when they reach adulthood; and women end up with postmenopausal lifespans just like ours.

By allowing their daughters to have more children, a few ancestral females who lived long enough to become grandmothers passed their longevity genes to more descendants, who had longer adult lifespans as a result.

Hawkes conducted the new study with first author and mathematical biologist Peter Kim, a former University of Utah postdoctoral researcher now on the University of Sydney faculty, and James Coxworth, a University of Utah doctoral student in anthropology. The study was funded by the National Science Foundation and the Australian Research Council.

How Grandmothering Came to Be

Hawkes, University of Utah anthropologist James O'Connell and UCLA anthropologist Nicholas Blurton Jones formally proposed the grandmother hypothesis in 1997, and it has been debated ever since. Once major criticism was that it lacked a mathematical underpinning -- something the new study sought to provide.

The hypothesis stemmed from observations by Hawkes and O'Connell in the 1980s when they lived with Tanzania's Hazda hunter-gatherer people and watched older women spend their days collecting tubers and other foods for their grandchildren. Except for humans, all other primates and mammals collect their own food after weaning.

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Grandmas made humans live longer: Chimp lifespan evolves into human longevity, computer simulation shows

By: Rebecca Jacobson

Photo by Susan Smith via Flickr.

Humans may have developed our long life spans as a result of nature's first babysitters: grandmothers. A new study published in the Proceedings of Royal Society B on Wednesday uses a mathematical model to determine how grandmothers can influence human longevity over the course of several generations, giving humans longer life spans than other primates.

This model revives a popular but often contested theory of human evolution known as the "grandmother hypothesis," which was first proposed in 1998 by Kristen Hawkes, an anthropologist at the University of Utah and senior author of Wednesday's study, and her colleague James O'Connell. The idea is that if grandmothers help feed and care for their grandchildren, mothers have more time and resources to devote to having another baby. And the more grandchildren she has, the greater chance grandma has of passing on the genes that allowed to her to live to such an old age, Hawkes said. This would also help explain why humans live long past their fertile years, something that is unique compared to other primates.

Hawkes thinks this new social cooperation and shifting life expectancy may have been the key to the evolution of humans from their australopithecine ancestors about four million years ago. And by caring for children other than their own, grandmothers may be the reason we became hyper-social, Hawkes said.

"So much of what makes us human may be a legacy of our ancestral grandmothers and ancestral babies," Hawkes said. "Just the pressure that it puts on babies to be better at engaging their caretakers...if it started with grandmothering, then it carried along a bunch of other things that we need to explain our life history."

Hawkes' theory has been embraced by some anthropologists, but others claim that changes in diet, hunting or human brain size had a greater role to play in shaping our modern selves. One of the criticisms was the theory lacked mathematical evidence that grandmothers alone could influence human longevity. Studies in 2010 and 2011 from the Max Planck Institute for Evolutionary Anthropology concluded that there were not enough women living past menopause to affect the life span of their descendants.

To challenge that finding, lead author and mathematical biologist Peter Kim at the University of Sydney created a mathematical model to simulate how long it would take to change the life span from one similar to our great ape ancestors to present hunter-gatherer groups. He adjusted the simulation to make grandmothers at least 45 years old and less than 1 percent of the female adult population. The model also stipulated that grandmothers could care for any children 2 years or older, not just her daughters' children.

Hawkes said the study did not include other factors such as brain size, hunting or pair bonding to show only the effect of grandmothering. In less than 60,000 years, human life expectancy doubled and the number of grandmothers in the population rose to more than 40 percent, similar to hunter-gatherer societies, Hawkes said.

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How Grandmothers Gave Us Longer Lives

Lawrence LeBlond for redOrbit.com Your Universe Online

Our grandmothers being there to care of us is something we all take for granted, and we have our ancestors to thank for that. New research indicates that human longevity is what it is because of grandmothers helping with childcare at an early stage in human history. Computer simulations on evolution have helped scientists prove that humans evolved longer life spans than apes because of their grandmotherly duties.

When it comes to chimpanzees, our closest primate relatives, females rarely live beyond their 30s, usually when their fertility usually ends. Although, based on the computer data, these female primates could evolve to extend their lifespan to those on par with human levels within 60,000 years if they took on a more grandmotherly role.

Previously, anthropologists have been divided as to whether humans long lives were due to the grandmother hypothesis or the hunting hypothesis. The computer simulations now show a stronger tie to the grandmother hypothesis.

Grandmothering was the initial step toward making us who we are, said Kristen Hawkes, a distinguished professor of anthropology at the University of Utah and senior author of the new study published in todays issue of the British journal Proceedings of the Royal Society B.

In the computer experiments, simulated creatures, generally lived another 25 years after reaching adulthood, much like chimps. But after 24,000 to 60,000 years of grandmothering duties, the simulated creatures lived another 49 years, on par with human hunter-gatherers.

The grandmother hypothesis states that when grandmothers help feed their grandchildren after weaning, their daughters can produce more children at shorter intervals. This theory also indicates that children becoming younger at weaning but older when they can first feed themselves and when they reach adulthood. The hypothesis also indicates that women who take on grandmotherly duties also end up with lifespans that go well beyond menopause.

Furthermore, by allowing their daughter to have more children, ancestral females who lived long enough to become grandmothers passed their longevity genes on to their descendants, who had longer lifespans as a result.

Another suggestion, based on the simulations, is that grandmothers may have even been responsible for increasing humans brain size by allowing mother to have larger families, increasing the pressure of natural selection. Bigger brains made early humans more capable of learning better hunting techniques and clever use of hunting weapons. The increased brain size in our ape-like ancestors was the major factor in humans developing lifespans longer than apes.

Hawkes conducted her study with the aid of mathematical biologist Peter Kim, a former University of Utah postdoctoral researcher now with University of Sydney, and also James Coxworth, a University of Utah doctoral student in anthropology.

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Humans Evolved To Live Longer Because Of Grandmothers

Computer simulation shows how with a little grandmothering animals with chimpanzee lifespans can develop human lifespans in 60,000 years Grandmothers would have helped to dig up tubers and crack nuts while younger adults got on with childrearing and hunting

By Daily Mail Reporter

PUBLISHED: 17:26 EST, 23 October 2012 | UPDATED: 17:26 EST, 23 October 2012

Human longevity is all thanks to our grandmothers' efforts to care for their family, new research suggests.

A theory that humans evolved longer adult lifespans than apes because grandmothers helped feed their grandchildren has been proved by a computer simulation of evolution, scientists claim.

Until now anthropologists were divided as to whether humans long lives were down to the 'grandmother hypothesis' or 'hunting hypothesis.'

Crucial to our evolution: Grandmothers who lived on to help with feeding their daughters offspring helped to pass on the longevity gene to future generations, scientists now believe

The grandmother hypothesis says that when grandmothers help feed their grandchildren after weaning, their daughters can produce more children at shorter intervals.

Because more children are born a few ancestral females who lived long enough to become grandmothers passed their longevity genes to more descendants, who had longer adult lifespans as a result.

See more here:
Thanks grandma! Human longevity 'down to older females who carried on caring for their offspring's young families'