Evolutionary anthropologist Rachna Reddy, a 2025-2026 fellow at the Harvard Radcliffe Institute, discussed her research on adolescence during a presentation on May 13. Reddy studies chimpanzees and bonobos to better understand why humans experience a prolonged period of adolescence compared to other species.
The topic is significant because adolescence is a vulnerable stage shared by humans and our closest evolutionary relatives. Most species transition quickly from puberty to adulthood, but both humans and great apes linger in this intermediate phase. By comparing these experiences, researchers hope to learn more about the development of social skills and relationships.
“When we share a trait with both [those] species, it’s good evidence that our last common ancestor probably also had that trait,” said Reddy. “Chimpanzees and bonobos in particular can really help us establish patterns that are universal in humans, so we can understand a bit more about ourselves.”
Reddy’s findings draw from over ten years of fieldwork at the Ngogo Chimpanzee Project in Uganda’s Kibale National Park. She explained that chimpanzee adolescence involves moving away from caregivers and forming new social bonds within their fission-fusion societies. Juvenile chimps stay close to their mothers until puberty but then must navigate uncertain social situations alone, sometimes displaying signs of anxiety before joining groups.
“In adolescence, chimpanzees receive threats they have never experienced before and likely never will again,” said Reddy, who is also an assistant professor at the University of Utah. Despite these risks, adolescent chimps actively invest in building relationships through grooming behaviors even when not reciprocated. “It suggests that puberty in chimpanzees is really intensifying these social motivational proclivities, despite risks,” she said.
For female chimps especially, early adolescent experiences can determine lifelong status as they leave their birth groups for new communities—a rare pattern among animals. “Adolescent females are making this super high-stakes first impression, it appears,” said Reddy.
Reddy concluded by suggesting parallels between human and ape development: “Learning to contribute is a really critical part of this stage, whether it’s in a relationship or to your community.”
