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The grandmother hypothesis: Grandma may help you live longer

Published: Monday, Aug. 3 2015 2:52 a.m. MDT

Diana Nevins reads to her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News) Diana Nevins reads to her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News)

SALT LAKE CITY — New mathematical simulations support the idea that grandmas do even more good than their homemade treats, creative handicrafts, encouraging words and helping hands already do.

A new study by University of Utah anthropologists says that as humans evolved, females whose childbearing years were ending were able to step in and help weaning children forage for food and other necessities, allowing mothers to focus on having more children.

It was further support to the "grandmother hypothesis," a brainchild of Kristen Hawkes, a University of Utah professor of anthropology and lead author of the study.

"Grandmothering was the initial step toward making us who we are," Hawkes said.

The study was published this week in the British journal Proceedings of the Royal Society B.

Diana Nevins plays with her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News) Diana Nevins plays with her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News)

The idea of grandmothering has been shown to not only give aging women an extension to their maternal purpose, resulting in an increased lifespan, but also to pass longevity genes to more descendants, who have longer adult lifespans as a result.

For Diana Nevins, becoming a grandmother was "the best news in the whole world."

Nevins, who lives in Spanish Fork, has four grandchildren but feels privileged to watch one of them, Lincoln, through much of the week while his parents work and go to school.

"It is important to spend time with them, be there for them and be their greatest and best fan," she said.

Nevins and her husband moved their life from Missouri, selling a house and buying a new one, to be in Utah for Lincoln.

Diana Nevins reads to her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News) Diana Nevins reads to her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News)

"It was a giant leap of faith, but it has been worth every minute," she said.

Influencing children

An older grandson, Nevins said, attends BYU and comes over for Sunday dinner every other week. And she Facebook chats with a granddaughter every once in a while. It's all part of an attempt to be "a big part of their lives," which Nevins strives to be.

"That grand-baby is a part of your child, who you love so much. It is sort of an extension of that, another little person that stems from that," she said. "It's fun to see them grow and learn. I don't remember my children learning as quickly as Lincoln is."

Nevins, 61, said she feels different being a grandmother than being a mother, less responsibility maybe, as her grandchildren always go home at the end of the day to their parents. Having less to worry about as a mature adult, she said she can focus more on the happiness of her grandchildren, and that brings her joy.

Diana Nevins plays with her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News) Diana Nevins plays with her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News)

"I think I realized that housework isn't as important as being with my grandchild," Nevins said. "The things I thought were important aren't so much. The time with him is more important."

She said the kids can learn things from her that they might not encounter elsewhere, including unconditional love.

"There are no strings attached with grandma and grandpa love. It's there all the time," Nevins said. And while Lincoln's demands are simple now — he's 18 months old — he appreciates the routine at grandma's house, which includes meals, playtime, a ride around the neighborhood on grandpa's scooter, and reading lots and lots of books.

Hawkes' hypothesis stemmed from observations conducted with another University of Utah anthropologist and co-author of the new study, James O'Connell, in the 1980s when they lived with Tanzania's Hazda hunter-gatherer people and watched older women spend their days collecting food for their grandchildren.

Diana and Wes Nevins play with their grandson Lincoln Reynolds at their home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News) Diana and Wes Nevins play with their grandson Lincoln Reynolds at their home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News)

Except for humans, all other primates and mammals collect their own food after weaning, she said.

But as the population evolved, researchers have noted environmental changes that led to a scarcity of food.

"So moms had two choices," Hawkes said. "They could either follow the retreating forests, where foods were available that weaned infants could collect, or continue to feed the kids after the kids are weaned. That is a problem for mothers because it means you can't have the next kid while you are occupied with this one."

Other women were able to step in and help, showing a benefit to grandmothering, also allowing the population to continue to grow and flourish.

"My grandparents died before I was born, so it took me becoming a mom to know about the influence of the backup team known as grandparents and power aunts," said Cori Connors, a Farmington resident, mother, grandmother and musician.

Diana Nevins plays with her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News) Diana Nevins plays with her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News)

Connors said her mother would pay the kids to learn and recite poetry, which encouraged them to become poets, songwriters, musicians and patrons of the arts "because she was astute enough to bribe them."

She said she misses her mother's influence.

The research

The computer simulations involved in the new University of Utah study help to support the grandmother hypothesis, measuring a change in adult longevity over time.

Chimps that reach adulthood (age 13) live an average of another 15 or 16 years, without help from a grandmothering figure. People in developed nations who reach adulthood (about age 19) live an average of another 60 years or so, to the late 70s or early 80s.

The simulation begins with only 1 percent of women living to grandmother age and able to care for grandchildren, but over 24,000 to 60,000 simulated years, about 43 percent of adult women are grandmothers, according to the study.

Lincoln Reynolds carries his grandfather Wes Nevins' cane at Nevins' home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News) Lincoln Reynolds carries his grandfather Wes Nevins' cane at Nevins' home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News)

From adulthood, additional years of life doubled from 25 years to 49 years from the beginning to the end of the simulated length of time.

"Grandmothering gave us the kind of upbringing that made us more dependent on each other socially and prone to engage each other's attention," Hawkes said.

The idea gave rise to "a whole array of social capacities that are then the foundation for the evolution of other distinctly human traits, including pair bonding, bigger brains, learning new skills and our tendency for cooperation," she said.

"It's the best job in the whole world," Nevins said. "My mom used to say, 'I love you kids, but, oh my goodness, the love I have for my grandkids is unexplainable,' and now I know how she feels."

Diana Nevins reads to her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News) Diana Nevins reads to her grandson Lincoln Reynolds at her home in Spanish Fork Wednesday, Oct. 24, 2012. (Scott G Winterton, Deseret News)

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