Gorillas have a social structure more complex than we thought

The human social organization may have evolved much earlier than expected, according to a study of gorilla behavior.

Western lowland gorillas have more complex social structures than previously thought and forge everlasting links between distant relationships. They also develop social strata with striking parallels to human societies, say the researchers.

The study suggests that the origins of human social systems date back to the ancestor shared with gorillas rather than the social brain of hominins after the split of other primates.

Published in the Proceedings of the Royal Society B, the study uses more than six years of data from two research sites in the Democratic Republic of Congo, where scientists have documented the social exchanges of hundreds of lowland gorillas. Where is.

Dr. Robin Morrison, a biological anthropologist from the University of Cambridge, and the research team observed that gorillas lived in small family units – a dominant male and several females with offspring – or single solitary .

They badyzed the frequency and duration of badociations. According to the data, there was a level of regular interaction – an average of 13 gorillas – which corresponded closely to the extended family dispersed in traditional human societies, such as aunts, grandparents and cousins.

Another level of badociation involved an average of 39 gorillas, similar to an "aggregated group" that spends time together without necessarily being closely related.

"An badogy with the first human populations could be a tribe or a small colony, like a village," said Dr. Morrison.

When silverbacks were half-siblings, they were more likely to be part of the same tribe. But more than 80% of nearby badociations detected were between silverbacks linked more distantly, or even apparently unrelated, the study indicates.

Dr. Morrison said, "Women, throughout their lives, have spent time in multiple groups, allowing men who do not have close relatives to grow up in the same birth group, at the same time. like half-brothers. The links that form can lead to those badociations that we see in adulthood.

"If we think of these badociations in a human-centered way, the time spent with each other might be badogous to an old friendship."

Researchers have discovered allusions to an even higher social level of periodic aggregations, similar to an annual gathering or festival based on "successful events".

Although they said they are too rare to be detected with certainty from the data in this study. Dr. Morrison says that the sporadic fruiting calendars of the gorillas' favorite foods may be one of the reasons why they – and therefore perhaps ourselves – have developed this "hierarchical social modularity".

She said: "Western gorillas often roam several kilometers a day to feed on a wide range of rare and unpredictable fruit plants. This food is easier to find if they collaborate when foraging. "

A small number of mammal species that also depend on idiosyncratic food sources have a social structure similar to that of humans. They also have space memory centers in their brains that compete with those of humans.

Previously, species on this short list were far removed from humans. Chimpanzees, members of the human family, live in small territorial groups with fluctuating and very aggressive alliances with their neighbors.

One theory for human society is that it requires the evolution of a particularly large and sophisticated "social brain" unique to the lineage of hominins. However, the study suggests that the addition of gorillas indicates that the simplest explanation could be that human social complexity has evolved much earlier and that it is simply absent from the lineage chimpanzees.

Dr Morrison said, "While primate societies vary a lot from one species to another, we can now see an underlying structure in gorillas that was probably present before the divergence of our species, a structure that is surprisingly good for a model of human social evolution.

"Our results provide further evidence that these endangered animals are profoundly intelligent and sophisticated, and that we humans may not be as special as we might think."

Researchers used statistical algorithms to reveal patterns of interaction between family groups and individuals in datasets.