The wild chimpanzees at Tanzania’s Gombe Stream National Park are at the heart of Jane Goodall’s groundbreaking research. Now, for the first time in decades, behavioral scientists have revisited some of Goodall's original observations of the animals' personalities.

The new study provides fresh insight, suggesting that, like humans, chimpanzee personalities are stable over time—a discovery that could help scientists test ideas for how our own temperament evolved.

“It’s the most famous groups of chimpanzees in the world, and I thought this was a terrific opportunity,” says study leader Alexander Weiss, a psychologist at the University of Edinburgh.

“Studying personalities in zoos has its advantages, but if you want to ask questions about something like [whether] personality is related