Extensive maternal care is a central factor for the longevity of animals and humans, modeling study suggests

The relationship between mother and child may provide clues to the mystery of why humans live longer than expected for their size – and shed new light on what it means to be human.

“It’s one of the really mysterious things about humans, the fact that we live super long lives compared to so many other mammals,” says Matthew Zipple, Klarman Postdoctoral Fellow in Neurobiology and Behavior in the College of Arts and Sciences. “What we’re putting forward is that part of the explanation for our longevity is this other fundamental aspect of our lives, which is the relationship between the mother and her child.”

The article ‘Maternal Care Leads to the Evolution of Long, Slow Lives’ was published in the Proceedings of the National Academy of Sciences on June 14.

In their models, Zipple and co-authors consistently found that in species where offspring survival depends on the longer-term presence of the mother, the species tends to evolve longer lives and a slower pace of life, which is characterized by how long an animal lives. and how often it reproduces.

“As we see these links between maternal survival and offspring fitness become stronger, we see the evolution of animals living longer and reproducing less frequently – the same pattern we see in humans,” Zipple said. “And the nice thing about this model is that it applies generally to mammals, because we know these connections exist in other species beyond primates, like hyenas, whales and elephants.”

Zipple and co-authors provide a universal mathematical model demonstrating the relationship between maternal survival and offspring fitness, on the one hand, and the pace of life, on the other. Two additional empirical models include the types of data on maternal survival and offspring fitness collected by field ecologists. Zipple said the hope is that these models can be further tested and used by field ecologists to predict how maternal care and survival influence the evolution of a species’ lifespan.

“We hope we’ve made the model simple enough that field ecologists can apply their existing long-term demographic data, which they’ve been collecting for decades, to this model and come up with this estimate of how much they expect.” mother’s care shaped the evolution of their study system,” Zipple said.

The work builds on the Mother and Grandmother Hypothesis, based on observations in human populations from the 18th and 19th centuries, that offspring are more likely to survive if their mothers and grandmothers are in their lives. This theory has primarily been used to explain menopause in humans, Zipple said, because cessation of reproduction reduces the risk of death and allows older women to focus on caring for their grandchildren.

Zipple’s models are both broader and more specific, encompassing more ways in which a mother’s presence or absence in her offspring’s lives affects their fitness. The team makes predictions, based on results from Zipple’s doctoral research in baboons and other primates, about how offspring fare if a mother dies after weaning but before sexual maturation of the offspring. Zipple found that this leads to both short- and long-term, even intergenerational, negative effects on primate offspring and grandchildren.

“We wanted to expand the mother and grandmother hypothesis to look at these specific ways in which we know in primates that the mother’s survival benefits her offspring,” Zipple said. “And ask what are the broader and perhaps subtler ways in which the benefits of maternal presence in one’s life can lead to the evolution of longevity. We are also trying to explain this phenomenon for a much broader range of animals.”

For Zipple, who spent six months observing mother baboons with their babies in the field during his doctoral research, the link between motherhood and longevity reinforces his observations and underlines the importance and power of maternal care.

“When you see mothers and babies interacting in non-human primates, you can see from the babies’ faces that there is nothing more important in the world than their mother’s presence,” Zipple said. “So for me, the behavioral work, combined with the demographic studies, has really reinforced this common evolutionary thread that we share with our closest primate relatives – namely that there is a period when the whole world is our mother, and while that as the As time goes on, it never goes away. Part of the long-term ambition of this line of research is to link it to longevity, thus linking these two mysterious and central aspects of what it is to be human.

Co-authors include H. Kern Reeve, professor of neurobiology and behavior (A&S), and Orca Jimmy Peniston, Kenai Peninsula College at the University of Alaska Anchorage.