Why do people live so long? A new study suggests that maternal care could be a major part of it.
A study from Cornell University says that the reason why humans and other primates live so long can be explained, at least in part, by the mother-child relationship.
Maternal care leads to the evolution of “long, slow lives,” noted a study published Friday in the peer-reviewed journal Proceedings of the National Academy of Sciences.
“Humans are primates, and we live much longer lives than expected based on our body size, even compared to other primates. We also exhibit very long periods of intense mother-infant bonding that is unusual in animals,” lead author Matthew Zipple he told CBC News via email on Wednesday.
“In this study, we argue that the two are causally related, so that the intensity of the mother-infant relationship partially explains our long lives and the lives of other long-lived social mammals,” said Zipple, a postdoctoral fellow in neurobiology and behavior in the College of Arts and Sciences at Cornell University.
But because the authors link maternal care to longevity in humans and animals, some scientists worry that the findings could be harmful to human mothers if taken out of context.
The study authors looked at demographic trends — at the species level — and did not draw parallels with modern parenting or suggest that mothers should spend more time with their children.
But the connection between longevity and maternal care may tempt some people to think that way, said Amanda Watson, associate professor of sociology and anthropology at Simon Fraser University, who was not involved in the study.
At least one science news site has already pointed to the study as proof that “a mother’s love is a powerful force that shapes not only our childhoods, but potentially our entire lives.”
“Can mothers still feel pressure and tension when we read [study] headline, and could this headline be used as a weapon by some who want to seize freedom for women? Of course, but they shouldn’t,” Watson said.
No pressure, though
The researchers used modeling and empirical data to look at factors such as lifespan, maternal survival and offspring fitness in mammals. They made predictions based on Zipple’s research on baboons and other primates.
They were able to show that in species where the survival of the offspring depends more on the longer-term presence of the mother, such as primates (including humans), they tend to live longer and reproduce less often.
And it’s not just primates – the authors said the model also applies to other social mammals, such as elephants, hyenas and whales.
But it’s important to keep in mind what the authors mean when they say “maternal care” when interpreting the results, said Andrea O’Reilly, a professor in York University’s School of Gender, Sexuality and Women’s Studies, who was also not involved. in studio.
Care, in this case, refers to a long, intense period of bonding between mother and child that can affect the offspring’s survival to have children of its own.
It’s not the “hyper-vigilant helicopter, sign your babies up for three programs by six months of age” that so many mothers already feel pressured to do, said O’Reilly, who is known for establishing the academic discipline of motherhood studies and maternal theory.
“A lot of what we do in Western culture, at least for the last 30 or 40 years, is called care. Things that mothers should and must do. But I would say a lot of it has nothing to do with taking care of Children, it’s all about having good mothering to mark you as a good mother,” O’Reilly told CBC News.
Her concern is that such a misinterpreted study could be harmful to mothers who already face “impossible standards.” And he notes that this wouldn’t be the first time research has caused mothers to feel guilty, specifically pointing to bonding studies that say the first hour of a baby’s life is the most important for maternal bonding.
“So many mothers couldn’t bond immediately with their baby for various reasons – medical or psychological – and lived with such shame and blame. So I’m just worried that this study, in the wrong hands, is a way to regulate control and resistance to mothers.” O’Reilly said.
“The last thing mothers need is another study that says ‘Oh my God, you need to do more for your baby’.”
A postpartum retreat in Toronto offers new mothers round-the-clock care, similar to services popular in China and South Korea. But one family doctor says the parents who need help the most are likely to be kicked out of posh residences.
No ‘right’ way to be a mother: study author
It’s important to keep in mind that the correlations found in the data do not examine the nature of the caregiving relationship, Watson noted.
“We’re talking about the evolution of many species over millions of years, not who should read a bedtime story,” Watson said.
Zipple, the author of the Cornell study, emphasized that his study is about evolutionary modeling to help us better understand our place in biological history.
“We all have mothers. Our mother is our first social relationship and for many people remains one of the most influential social relationships in their lives,” he told CBC News.
“For better or worse, we are also animals with complex social behaviors and relationships that have been strongly shaped by historical evolutionary forces.”
Evolution doesn’t distinguish between “good” and “bad” behavior the same way we do, he added.
“And so we should never assume that selective pressures from our evolutionary past can tell us the ‘right’ way to be a mother or a father or a friend or a partner or a citizen.”
Mother and grandmother hypotheses
The Cornell study builds on the “mother and grandmother” hypothesis, which is also used to explain menopause and why women live longer when they can produce more offspring.
Basically, the theories suggest that it is advantageous for older females to stop reproducing because they gain more evolutionary success by helping their children raise their grandchildren rather than having more children of their own, and the offspring are more likely to survive if their mother and grandmother are in their lives.
Scientists have previously applied the theory to killer whales and four species of toothed whales, the only mammals other than humans known to experience menopause. They even discovered that grandmother orcas stick around to help the mothers raise their calves.
(Not for nothing, but another recent study found that orca mothers who raise male offspring are half as likely to reproduce successfully again as those who have female ones. The researchers suggested that this may be because male offspring are more desirable and require more food ).
In this study, the authors note that they have extended the logic of the mother-grandmother hypotheses “to a more general form that we expect will have relevance across mammalian taxonomy.”
Simon Fraser University’s Watson says the mother and grandmother hypotheses should also be interpreted with “extreme caution”. He explains that scientists and anthropologists disagree on how to understand the correlations between the presence of grandchildren, advanced age and reproductive fitness.
Taken together, studies like this provide “exciting clues” about highly social species, including humans, Watson said.
“But they’re humorous at best when taken out of that context.”
Research indicates a significant shift over the past two decades in the number of North American adults planning to have children. Andrew Chang examines three main reasons for generational change.