Human beings have evolved to become the most flexible of all primates, a fact evident by the ability to survive in a multitude of social settings, claim researchers from Oxford and the University of Auckland.
The study analyzed patterns of social groups among living primates, as well as examining the family tree of 217 primate species. The researchers then used Bayesian data modeling to reconstruct the most likely explanations for how grouping behavior among primates evolved, over 74 million years ago.
The key finding is that the primary change in social behavior occurred when primates switched from being nocturnal to diurnal. Primates, scientists believe, started as solitary night-time foragers, allowing them better chances at surviving predators. However, the switch to daytime living meant they were more vulnerable to predatory action, unless they could show strength in numbers.
The current paper seeks to provide evidence showing that this switch in activity coincided with a significant change in social behavior; primates, for the first time, started to "gang up". Researchers, therefore, concluded that social bonding began as a way of adopting to a new threat.
The study also suggests that primates went from being solitary foragers to living in large, mixed-sex groups that allowed members the freedom to come and go as needed; a sort of behavior still observed in some primates like lemurs.
"There is an amazing flexibility in the way humans have managed to socialize, network and live together, both in groups and wider society. We have a huge variety of social settings to cope with, according to the different cultural practices and customs," said one of the authors of the study, Susanne Shultz, in a statement.
"This flexibility in the human lineage has not evolved to anything like this level in other primates. Our findings support previous studies that suggest that more brain power is needed for groups that have a more complicated social life," she added.
The data used for the study included a huge range of social grouping platforms, drawn from individuals, family-bonds, pair-bonds, harems and multi-male and multi-female groups. Researchers discovered that primate bonding behavior was strongly influenced by their ancestors, with closely related species having similar social behavior.
The transition to group living took place, approximately, 52 million years ago and, since then, in both human beings and primates, there has been no shift back to individual-based patterns. Essentially, primates that began living in pairs did not switch back to group living, whereas those that began living in large groups could move between such groups easily.
"These (findings) allow us to look back in time to understand major step changes in social evolution amongst our closest relatives. We now understand why primate sociality is inherently special, as bonded social groups are unusual in mammals, yet the norm in primates," said the study's co-author, Kit Opie.