Extended maternal care is a central factor in animal and human longevity, a modeling study suggests

The relationship between mother and child may offer 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 puzzling things about humans, the fact that we live these super-long lives compared to so many other mammals,” said Matthew Zipple, Klarman Postdoctoral Fellow in Neurobiology and Behavior in the College of Arts and Sciences. “We suggest that part of the explanation for our long lives is this other fundamental aspect of our lives, which is the relationship between a mother and her child.”

The article “Maternal care leads to the evolution of long, slow lives” was published in 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 the animal lives. and how often it reproduces.

“As we see these links between maternal survival and offspring fitness strengthen, we see the evolution of animals that live longer and reproduce less often — the same pattern we see in humans,” Zipple said. “And the nice thing about this model is that it’s general to mammals in general, because we know that these links exist in other species outside of primates, like hyenas, whales, and elephants.”

Zipple and co-authors provide a universal mathematical model that demonstrates the relationship between maternal survival and offspring fitness on the one hand and the pace of life on the other. Two other empirical models incorporate 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 will affect the evolution of a species’ lifespan.

“We’re hoping that we’ve made the model straightforward enough that field ecologists can take their existing long-term demographic data that they’ve been collecting for decades and apply it to this model and come up with this estimate of how many to expect.” mother’s maternal care shaped the development of their learning system,” Zipple said.

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

Zipple’s models are broader and more specific, encompassing multiple ways in which a mother’s presence or absence in her offspring’s life affects her offspring’s fitness. Based on Zipple’s doctoral research on baboons and other primates, the team predicts how the offspring will fare if the mother dies after weaning but before the offspring reaches puberty, which Zipple found leads to short- and long-term, even intergenerational, negative effects to primate offspring and grandchildren.

“We wanted to extend the mother-grandmother hypothesis to look at these particular ways that we know in primates that the mother’s survival benefits her offspring,” Zipple said. “And ask what are the broader and perhaps more subtle ways in which the benefits of maternal presence in human life may lead to the evolution of longevity. We are also trying to explain this phenomenon across a much wider range of animals.”

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

“When you watch mother-infant interactions in primates, you can see in 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 – which is the time when the whole world is our mother, and it will wane over time, it will never go away. Part of the long-term aspiration of this line of research is connecting that with longevity, connecting these two mysterious and central aspects of what it means to be human.”

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