Some gorilla social bonds may be analogous to “old friendships” and “tribes” in humans, say researchers.

Silverback males Dwayne and Sangha, the dominant males of two different western gorilla groups, feed peacefully together in Mbeli Bai forest clearing. Credit: Wildlife Conservation Society. Silverback males Dwayne and Sangha, the dominant males of two different western gorilla groups, feed peacefully together in Mbeli Bai forest clearing. Credit: Wildlife Conservation Society.

Gorillas have more complex social structures than previously thought, from lifetime bonds forged between distant relations, to "social tiers" with striking parallels to traditional human societies, according to a new study.

The findings suggest that the origins of our own social systems stretch back to the common ancestor of humans and gorillas, rather than arising from the "social brain" of hominins after diverging from other primates, say researchers.

Published in the journal Proceedings of the Royal Society B, the study used over six years of data from two research sites in the Republic of Congo, where scientists documented the social exchanges of hundreds of western lowland gorillas.

"Studying the social lives of gorillas can be tricky," said lead author Dr Robin Morrison, a biological anthropologist from the University of Cambridge. "Gorillas spend most of their time in dense forest, and it can take years for them to habituate to humans."

"Where forests open up into swampy clearings, gorillas gather to feed on the aquatic vegetation. Research teams set up monitoring platforms by these clearings and record the lives of gorillas from dawn to dusk over many years."