Chimp sons like to hang with fathers and brothers

A young adult chimp grooms and older male in Kibale National Park, Uganda. (Credit: Aaron Sandel/UT Austin

Even if they have no way of identifying them, male chimpanzees form intimate bonds with their fathers, according to a new study of wild chimpanzees in Uganda.

In adulthood, male chimpanzees form strong relationships with one another. These bonds can be mutually beneficial—to relieve stress, protect one another, and share food.

In the new study, which examines when and with whom these bonds develop, researchers discovered that chimpanzees most often bond with their maternal brothers and old males, including—seemingly unbeknownst to the younger chimps—their biological fathers.

“Elements of fatherhood may have arisen in a chimpanzee-like social system before mates formed pair bonds.”

“Fatherhood is really a social relationship that happens to be linked to a genetic relationship. In humans, it is strongly correlated because humans tend to form pair bonds,” says Aaron Sandel, assistant professor of anthropology at the University of Texas at Austin.

“Usually we think that pair bonds evolved in humans first, and then fathers came to play an active role. However, my findings suggest that elements of fatherhood may have arisen in a chimpanzee-like social system before mates formed pair bonds.”

Old retired males

For the study in the American Journal of Primatology, researchers studied the social relationships of 18 adolescent and young adult (12-21 years old) male chimpanzees at Ngogo in Kibale National Park, Uganda, over the course of one year.

The researchers found that by age 12, about the time chimpanzees begin to regularly travel independently from their mothers, male chimpanzees form strong friendships with other males in their communities.

These relationships range in intimacy, from associating in the same subgroup, where they travel, rest, and feed together; to spending time in proximity, a tighter-knit group that stays within about 15 feet of one another; to grooming, where they use their fingers to comb through each other’s hair.

“For humans, you can imagine association, proximity, and grooming as if you were at a coffee shop,” Sandel says. “You’re in association with everyone at the coffee shop. You’re in proximity to others at the same table or one table away. And if you have a private conversation with someone, that’s like grooming.”

Through observation and fecal sampling, researchers found that the younger males tended to associate and spend the most time in proximity to their maternal brothers. They shared many bonds with distantly related or unrelated males. Some bonds existed between peers. However, many of their closest relationships were with old, “retired” males, including their biological father.

“It’s as if chimpanzees have father figures and some of these are their actual father,” Sandel says. “This was surprising because chimpanzee females will mate with multiple males while ovulating, and there’s no paternal care in a chimp’s rearing. So, there is no reason to think that she or the males know who the father of her offspring is, and vice versa.”

Benefits of hanging out with fathers

There are benefits to bonding with an older, somewhat retired male, the researchers say. Older males are well connected in the community but are no longer competing for a position in the hierarchy.

It could be that the chimp’s biological father was high-ranking in the past, making him more likely to reproduce with females within the same territory and more likely to receive grooming from younger chimps looking to climb the social ladder, Sandel suggests.

The researchers propose that future research should examine the mechanisms of how father-son relationships might develop. But the fact that there is a relationship at all suggests that such bonds arise without a bond between parents and without the father caring for his offspring as an infant, two factors thought to be important for father-offspring relationships in humans.

Additional coauthors are from the University of Michigan and Arizona State University.

Source: University of Texas at Austin