More social species live longer

New research has revealed that species that are more social live longer and produce offspring for a greater timespan. This is the first study on this topic which spans the animal kingdom, from jellyfish to humans.

What are the benefits and costs of sociality? Social organisms may enjoy benefits such as sharing resources, being better protected from predators, and having support to raise offspring. However, by living in more tightly packed groups, social organisms may also suffer disadvantages such as the spread of disease, increased competition, aggression, and conflict.

A new study has carried out a comprehensive assessment on the link between sociality and different life history traits such as generation time, life expectancy, and the length of their reproductive window. Up to now, research evaluating the overall impacts of sociality on performance has focused on single species or groups, such as birds or some mammals. The new study assessed 152 animal species from a wide variety of taxonomic groups, including birds, mammals, insects, and corals.

The results of the study showed that more social species live longer, postpone maturity, and are more likely to reproduce successfully than more solitary species. While social species may not be the best to adapt and benefit from a rapidly changing environment, they are often more resilient as a group. This novel finding supports the hypotheses that, even though sociality comes with some obvious costs, the overall benefits are greater.

The study also revealed that sociality does influence the reduction in an animal’s ability to reproduce or survive as they age, known as senescence. For example, social allies may help protect against predation, increasing lifespan, but the stress of social hierarchies and conflicts can have the opposite effect.

What the researchers say: “Sociality is a fundamental aspect of many animals. However, we still lack cross-taxonomic evidence of the fitness costs and benefits of being social,” the lead author explained. “Here, by using an unprecedented number of animal species this work has demonstrated that species that are more social (most monkeys, humans, elephants, flamingos, and parrots) display longer life spans and reproductive windows than more solitary species (some fish, reptiles, and some insects)."

Whereas previous studies have tended to class sociality as a binary category (i.e. a species is either not social, or social), this new study recognized that sociality exists as a spectrum across animal species.* The continuum used included more ‘intermediate’ ways of sociality, such as being gregarious (e.g., wildebeests, zebras, flock-forming birds), communal (e.g., purple martin birds), or colonial (e.g., nesting birds, some wasps, coral polyps).

“In a post-COVID era, where the impacts of isolation have been quite tangible to humans (a highly social species),” the researchers added, “the research demonstrates that, across a comparative lens, being more social is associated with some tangible benefits.

So, what? A very interesting study. It fits in nicely with other recent studies showing that human individuals with higher levels of sociality also tend to live longer.