Rachna Reddy watched a young chimpanzee linger at the edge of a social gathering, whimpering softly before mustering the courage to approach. The scene, recorded during a decade of fieldwork at Uganda's Kibale National Park, captures something profound about the human condition: the peculiar pain and necessity of adolescence itself.
Most animals move swiftly from childhood to adulthood, but humans do something unusual—we linger in a vulnerable, often difficult teenage years. Evolutionary anthropologist Reddy, a 2025–2026 fellow at the Harvard Radcliffe Institute, discovered that our two closest living relatives, chimpanzees and bonobos, share this same trait. That parallel evolution suggests our protracted adolescence serves a real evolutionary purpose, not a cruel accident of biology.
For the past decade, Reddy has studied the Ngogo Chimpanzee Project in Kibale National Park, where researchers have been following the same population continuously since 1993. Her findings, presented in May, reveal that adolescence for chimps involves a radical social reorientation. Young chimps follow their mothers and caregivers until puberty strikes between ages 8 and 12. Then everything changes. The adults who once cuddled and played with them suddenly become sources of intense aggression and threat—what Reddy calls "threats they have never experienced before and likely never will again."
The surprise lies in how young chimps respond. Rather than retreating to safety, they do the opposite. Adolescent chimpanzees actively invest in relationships despite the anxiety and rejection. They initiate grooming behavior—a crucial reciprocal part of adult social bonds—even when other chimps don't groom them back. "Puberty in chimpanzees is really intensifying these social motivational proclivities, despite risks," Reddy explained. The young chimps push through rejection and social fear as if learning something essential.
The stakes are even higher for female adolescents. Unlike most species where males disperse, young female chimpanzees leave their natal group permanently and settle in new communities—another rarity in the animal kingdom. Researchers believe that a female's entire lifelong social status hinges on her first year in her new home. "Adolescent females are making this super high-stakes first impression," Reddy said. The data bears this out: adolescent females spend far more time than males watching adults groom one another and gather food, apparently preparing themselves for the social navigation ahead.
These observations reveal something crucial about human development. Our own adolescence, shaped by the same evolutionary pressures as our closest cousins, is fundamentally a learning ground—not just for competition, but for cooperation. Teenagers aren't simply being difficult; they're acquiring the capacity to hold down jobs, to contribute to their communities, to introduce themselves to strangers at parties. They're learning the tolerance for rejection and the persistence required to form lasting adult relationships.
"Learning to contribute is a really critical part of this stage, whether it's in a relationship or to your community," Reddy said. Understanding adolescence this way—as a hard-won evolutionary adaptation rather than a phase to endure—might transform how we see the teenagers in our lives. The whimpering at the edge of the social gathering isn't weakness. It's the sound of growth.