Scientists from a research center in Beijing (China) studied mammals that live in groups and provided new data relating the form of social organization of some species with their longevity. Among the nearly a thousand animals studied are the African elephant, the ring-tailed lemur or the horseshoe bat.
“The species that survive are not the strongest, but the ones that best adapt to change.”. This is one of the phrases that the scientist Charles Darwin left for posterity in 1859, in his book The origin of species.
In the case of mammals, they seem to have always needed others to survive. Throughout their existence, these animals have created communities, so cooperation has been an essential feature for their survival.
Now, a team of researchers at the CAS Key Laboratory of Animal Ecology and Conservation Biology in Beijing, China, suggests that mammals that live in groups live longer. Indeed, the study published in Nature Communications provides new clues to understand the interrelationship between sociability and survival in mammals.
The analysis results
“After analyzing nearly a thousand specimens, we found that species that live in groups generally have a longer lifespan than solitary species.” explains Xuming Zhou, the lead investigator. Among the specimens studied that live in communities are the Asian elephant, the African elephant, the ring-tailed lemur, the mountain zebra or the horseshoe bat. On the other hand, the solitary species studied include the dugong, the anteater or the eastern American squirrel.
It is known that mammals have different behaviors in the way they organize themselves socially: they are able to live alone, in pairs or in a community. Thus, to carry out this study, a comparative analysis of approximately one thousand mammals was carried out, divided according to their state of social organization and taking into account their survival. “The results show that mammals that live in groups survive evolutionarily longer than solitary ones.”, says Xuming Zhou.
For example, the lifespan of northern short-tailed shrews (which are solitary) was compared to that of large horseshoe bats (which live in groups), both of which are similar in weight. The maximum life expectancy of the former was approximately two years, while the latter could reach 30 years, according to the work.
Immunity, a key part
In order to find out which aspects can be decisive in the interconnection between both factors, the equivalent characteristics between individuals living in groups and the longevity factor were tracked. The researchers then identified 31 genes, hormones and common aspects related to immunity, through the transcriptomic analysis of about one hundred mammals. These data suggest that “Immunity and hormones are important both for controlling or regulating social organization and for longevity.says Xuming.
The study shows, however, that new analyzes of the molecular mechanisms underlying the evolutionary relationships between sociability and longevity, crucial to understanding their evolution, would be necessary, and that still “they are not clear“.
When it comes to identifying the differences between mammals that live in groups and those that prefer to live alone, the research highlights that gregarious individuals are less likely to die of hunger or other predators, according to the major researcher. Additionally, the strong, stable social bonds that form between group members can reduce adverse environmental cues or stress. Likewise, the scientist adds that characteristics such as the formation of coalitions or the way in which groups disperse, as well as mutual cooperation, can also influence their survival.
However, mammals that live in groups don’t just have advantages. The main researcher alludes, for example, to problems arising from competition for mating or access to food, when resources are limited (which can lead to greater stress), and even the spread of infectious diseases derived from social contacts. It is the “compensation” and/or the disadvantage of living together, in Xuming’s note.
Similarities of these mammals that live in groups with humans?
The variation in mammalian life expectancy is so great that it ranges from two years in shrews to over 200 years in some types of whales. It is known from previous research on species such as the chacma baboons that individuals with strong social ties live longer than those with weaker ones.
However, it is still too early to confirm that human life is determined by similar conditions. In this sense, Xuming is prudent: “this is a study that crosses data from different species, in which we did not explore the difference in life expectancy between solitary specimens, living in pairs or in groups within the same species”.
The researcher recalls that the maximum life expectancy of human beings is around 122 years, but the factors involved in their longevity may be more complex than those that affect other mammals, since, certainly, in this case, other aspects such as the impact information or medical care.
Reference:
Pingfen Zhu, Xuming Zhou et al. “Correlated evolution of social organization and life expectancy in mammals“. Nature Communications (2023)