Living in groups makes life more tolerable and tends to boost lifespan among mammals. A study from Chinese researchers, reviewing nearly a thousand species, shows that social species live longer than those that live alone.
Most mammals rely on other members of their species to survive, so many species form communities where partnership is vital for ongoing survival.
“Distinguish the link between sociability and longevity to gain a deeper view of how animal life evolved” is how the Beijing-based CAS Animal Ecology and Conservation Biology Main Laboratory researchers frame their work.
The central finding, published in Nature Communications, is straightforward: mammals living in groups tend to live longer. The team performed a comparative phylogenetic analysis across almost a thousand mammal species under three social arrangements solo, pair, and group, and explored how sociability relates to survival.
It was stated that species living in groups generally outlive those that are solitary, and the rate of moving from short to long lifespans is higher in group-living species. The report notes that social organization and longevity are connected in ways stronger than in nongroup species.
Whales can live up to 200 years.
In any case, the study compared different species, though it did not analyze life expectancy differences between solitary individuals and paired or grouped members within the same species.
Very different life expectancies
Mammals show a remarkable range in lifespan, from under two years in some shrews to more than two centuries in bowhead whales. Researchers found that species with similar body sizes can have markedly different lifespans, and in most cases group-living species fare better.
The scientists examined how shared traits between individuals in groups relate to longevity, aiming to uncover what aspects condition their reciprocal link.
Comparative brain transcriptomic analyses across ninety-four mammalian species identified thirty-one genes, hormones, and immune pathways commonly involved in social organization and longevity. Other selected traits revealed as many as twenty overlapping pathways under selection for both social structure and lifespan. These findings provide a molecular basis for how social life influences longevity.
Social ties can extend a species lifespan by reducing mortality and improving health and survival outcomes, according to the authors.
An illustration of a herd at a watering hole accompanies the discussion.
Other research includes female chacma baboons and rhesus macaques, where strong and stable social ties correlate with longer life, and herding animals show greater resilience against starvation or predator threats.
For humans, strong social connections are linked to lower risks of physiological dysregulation, including high blood pressure and stress, echoing earlier studies.
Group life also has its drawbacks
Not all advantages hold in every case: a negative association between close relationships and longevity has been observed in the yellow-bellied marmot. Conflicts over mates and food can also shorten life in some contexts.
Another challenge of group life is the potential spread of parasites. Species living in groups face higher contact rates and closer interactions, which can increase disease risk. Yet social species often develop stronger immune defenses to mitigate these risks.
An example of a shrew highlights the discussion.
The rhythm of life offers another possible link between social life and longevity, reflecting how an organism allocates resources between survival and reproduction.
The authors describe a fast life history with rapid development and high reproductive rates, versus a slow life history with slower development and longer lifespans. They acknowledge that more work is needed to fully understand the molecular mechanisms behind the evolutionary ties between social organization and longevity.
Reference: Nature Communications, s41467-023-35869-7 [citation attribution].
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