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Many of us owe our mothers our survival into adulthood. However, the protective “cuddle” of a mother’s love can extend far beyond the individual.
A exceptional longevity of the entire human race can be partially explained by the length of time children remain under the mothers care.
A 2024 study in PNAS on animals that live long, slow lives, including primates, whales and hyenas, focuses on a trait these species have in common. The young of all these species remain dependent on maternal care for long periods of time.
According to the team of researchers at Cornell University, the research suggests that natural selection over time tends to favor mothers who live longer – helping to drive the evolution of longer lives in the species.
Of course there is an evolutionary compensation. These long-lived species produce fewer offspring than, for example, a litter of kittens or a bag of tiny spiders. But this also benefits the offspring, allowing more care for each offspring.
“One of the really mysterious things about humans is the fact that we live extremely long lives compared to other mammals,” noted neurobiologist Matthew Zipplewho led the investigation.
“What we propose is that part of the explanation for our long life expectancy is this fundamental aspect, which is the relationship between mother and her child“, he explained.
As life expectancy of mammals they vary widely, from a brief 12 months for Müller’s Sunda rat to the two centuries of lifespan for the bowhead whale. For most species, their life expectancy is vague but reliable relationship to body size.
Some species, however, defy this relationship, with life expectancies much higher than those of other species with similar body mass.
Os Humans are among these longest-lived speciesas well as some other primates, as well as hyenas, certain species of whales and elephants. What these species also have in common is the fact that they are all very social, living in groups that help each other.
Grandmother Hypothesis
One proposed explanation for the longevity of at least some of these species is the Grandmother’s hypothesis. According to this theory, in species with a post-menopausal phase of life, grandmothers stop reproducing, reducing reproductive competition and giving support for mothers who are still having children.
However, this only applies to a few species – humans, killer whales, beluga whales, narwhals and possibly chimpanzees.
And then the chance for… Mom
Zipple wanted to understand why other species without postmenopausal grandmothers can live equally long lives, Focusing your attention on mothers.
Researchers have built models to test the extent to which a mother’s survival affects the survival chances of her offspring – and even her grandchildren.
The idea is simple. In many of these long-lived species, the The death of a mother or grandmother reduces the chances of survival of their offspring.
This suggests that in species where young depend heavily on their mothers, having a mother stay alive longer can directly improve her offspring’s chances of survival and reproduction.
This creates evolutionary pressure to favor individuals who live longereven if they have fewer descendants in total.
Across multiple models, the team found the same pattern. When offspring depend more on their mothers, Populations tend to evolve towards longer lives and slower reproduction.
Conversely, if a mother dies early, her offspring may be less healthy or less able to care for their own offspring, creating an impact on cascade in survival across generations.
In the species in which these connections were studied, it was also found that the strength and duration of the mother’s influence are greater than that of the father.
“When we observe mothers and offspring interacting in non-human primates, we can simply see in the infants’ expressions that There is nothing more important in the world than a mother’s presence“, disse Zipple.
