Extended parental care is vital for humanity's success as a species, so its evolution is important to understand. An unexpected observation of father-son bonds among adult chimpanzees has thrown into question the dominant theory of how humanity's male ancestors came to care for their offspring.
“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,” said Dr Aaron Sandel of The University of Texas at Austin in a statement. “Usually we think that pair bonds evolved in humans first, and then fathers came to play an active role.”
Now Sandel is not so sure. In the American Journal of Primatology, he describes his observations of 18 male chimpanzees aged 12-21 years in Kibale National Park, Uganda. Twelve is about the age when male chimps cease to depend on their mothers, instead bonding with other males. As with other social animals, these bonds are not all equal – an adolescent male chimpanzee will have some bros he grooms frequently and maintains tight proximity to, while with others it is more of a loose association.
"For humans, you can imagine association, proximity and grooming as if you were at a coffee shop," Sandel said. "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." (IFLScience advises humans against taking this too literally by running fingers through conversation partners' hair without permission.)
Sandel combined the sort of detailed tracking of chimpanzee grooming and proximity networks primatologists have been conducting for years with genetic analysis of their feces. To everyone's surprise, he found young chimps disproportionally connected with their biological fathers.
"It's as if chimpanzees have father figures and some of these are their actual father," Sandel said. This is unexpected because chimpanzees frequently mate with more than one male when ovulating. Since the young chimps can't read Sandel's genetic notes, they're as ignorant of who their father is as Jon Snow and Luke Skywalker at the start of their respective epics. Moreover, it is not like the fathers provide any child support to their offspring during the early years of life.
Whatever forces bring father and son chimps together, the teaching and support of a wise elder has an obvious evolutionary benefit. Moreover, assuming the connections Sandel observed were more than a statistically improbable coincidence resulting from a modest sample, paternal bonds can apparently arise without an ongoing connection between the parents. This, in turn, challenges the idea that long-term pairing between parents was a necessary predecessor for the appearance of paternal care.