Fight Aging!

The grandmother hypothesis suggests that human longevity relative to other primates and large mammals evolved because grandmothers act to improve the reproductive fitness of the offspring of their daughters. This provides a selection pressure to increase the odds of survival into later life, and since cultural transmission doesn't require physical fitness per se, it allows for frail elders to evolve. The same sort of process appears to operate in killer whales. The grandmother effect might be considered a case of particularly extended maternal care, and researchers here discuss a model of evolutionary processes in which a link emerges between length of maternal care of offspring and species life span. This manifests not just over evolutionary time, but is evident in human and primate demographics, in which presence or absence of mother or grandmother produces a sizable difference in outcomes for the offspring.

Researchers found consistently 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 life pace, 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 grow stronger, we see the evolution of animals having longer lives and reproducing less often - the same pattern we see in humans. And what's nice about this model is that it's general to mammals overall, because we know these links exist in other species outside of primates, like hyenas, whales, and elephants."

The researchers constructed a universal mathematical model that demonstrates the relationship between the maternal survival and fitness of offspring on the one hand, and on the other, pace of life. Two additional empirical models incorporate the types of data about maternal survival and offspring fitness collected by field ecologists. The hope is that these models can be further tested and utilized by field ecologists to predict how maternal care and survival impacts the evolution of a species' lifespan. "We hope 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 much they expect mother's maternal care to have shaped the evolution of their study system."

The work builds off the Mother and 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 new models are both broader and more specific, incorporating more of the ways that a mother's presence or absence in her offspring's life impacts its fitness. The team makes predictions, based on research on baboons and other primates, about how offspring fare if a mother dies after weaning but before the offspring's sexual maturation, which researchers have found leads to short-term and long-term, even intergenerational, negative effects on primate offspring and grand-offspring.

Link: https://news.cornell.edu/stories/2024/06/mothers-care-central-factor-animal-human-longevity