Mammals that live in groups may live longer, longitudinal research suggests

For mammals, one secret to a long life is spending time with friends and family.

An analysis of the life spans and social lives of nearly 1,000 mammal species shows that species that live in groups, such as horses and chimpanzees, tend to live longer than solitary animals such as weasels and hedgehogs. The finding suggests that life span and social traits are involved in the evolution of mammals, the researchers report on January 31. Nature Communications.

The maximum lifespan of mammals ranges widely. The shortest-lived shrews, for example, live about two years, while bowhead whales (The mystic whale) can be about 200 years of age (SN: 1/6/15).

When evolutionary biologist Xuming Zhou of the Chinese Academy of Sciences in Beijing was studying the longest-lived mammals to understand the evolution of length, he took the main characteristics of naked mole rats.Heterocephalus glaber). Moles are extremely long-lived, sometimes reaching over 30 years of age. They also live in huge, complex, underground societies. In contrast, other murres such as the golden hamster (Mesocricetus auratus) which are solitary, they hardly live only four years.

Some previous research on specific mammal species has shown an effect of social behavior on longevity, Zhou says. For example, the chimpanzee female chacma (Papio Ursinus) with strong and stable social bonds live longer than women without them.

Zhou and colleagues decided to see if there were links between longevity and social habits shared across a wide range of mammal species.

The researchers compiled information from the scientific literature on social issues for 974 mammal species. They then divide these species into three types: solitary, pair-living, and group. When the researchers compared these three groups with data on mammalian longevity characteristics, they found that group-living mammals lived longer than solitary species — about 22 years compared to about 12 years in solitary mammals.

Zhou and colleagues then assessed for body mass—larger mammals tend to live longer than smaller ones—and the effect of social bonds held. An example of minya from shrews and bats. Both mammals are similarly small, but the more robust shrews live for a few years, while some species of bats, far more social, can live for 30 or 40 years.

“So we were surprised that individuals who live in groups are also involved in a lot of costs, such as the potential for meeting mates and competition for food,” Zhou says. Frequent social contact in group settings can encourage the spread of infectious diseases.

But they are, he says, good for living together, as a grouping for protection against predators. Eating can also reduce the risk of starvation if, for example, group members increase foraging efficiency by finding and gathering food. These social mammals can live longer.

The evolution of long life may be even more likely in living species: Living in a circle allows animals to potentially help survive their domesticated mates, which carry their genes.

Laurent Keller, an evolutionary biologist at the University of Lausanne in Switzerland, praises the study for the sheer size of the sampling work. “But it would have been useful to be somewhat more specific about the various levels of sociality.” There are many variations of social class within the three categories used in the study, he says, and the relative level of sociality in any patterns you see.

However, fine-tuning social categories “is not an easy task,” Cellarius notes.

To get an idea of ​​how genes might produce a link between longevity and group living, Zhou and his team took brain tissue samples from 94 mammalian species and developed transcriptomes — the full complement of RNA — for insights into different gene levels. This can reveal whether genes are turned on or off, or how much protein the genes are able to instruct the cells to produce.

The researchers found 31 genes whose levels of relative activity correlated with longevity and one of three social-prescribed genes. Many of these genes appear to have roles in the immune system, which may be important when pathogens spread through social groups. Other types of hormones have been associated with regulation, including some thought to stimulate social behavior.

By studying these genes in more detail, Zhou provides more insight into how mammals’ behavior and life spans evolve simultaneously.