Male gorillas have a reputation for taking a hard line on male outsiders who wander into their clan’s neighborhood. Field studies show that 9 out of 10 such meetings lead to displays of aggression, with 1 in 5 ending in fighting. Now scientists have found a notable exception in Central Africa, where lowland gorillas have developed an unusual peace pact.
When head males from adjacent areas encounter each other, hostility is relatively rare, says Diane Doran Sheehy of the Mondika Research Center, located on the border between the Democratic Republic of the Congo and the Central African Republic. “The males will tolerate other males feeding near them or even getting almost close enough to touch the females,” she says. This tolerant behavior started to make sense once Sheehy and geneticist Brenda Bradley of the Max Planck Institute in Germany analyzed DNA from 12 lowland gorilla groups. Head males from neighboring clans had a high probability of being first-degree relatives, implying that the animals have formed a giant male kinship network—a sort of superfamily. This network discourages violence, Sheehy speculates, because peaceable interactions may help related males set up their own territories and attract mates, thereby increasing the likelihood that shared family genes get passed on.
Such behavior contrasts sharply with that of the better-known mountain gorillas. “Mountain-gorilla males are more likely to remain with the group they were born in, while females change groups looking for unrelated mates,” Sheehy says. Competition for unattached females can be fierce between neighboring groups of males,
so fights happen often. Sheehy suggests that the lowland gorillas’ lifestyle may offer us a glimpse of our own past. Similar male kinship networks in humans may have led to the extended, stable interactions that formed the basis of early society.