Thomas Gillespie’s parents and teachers always wanted him to go into medicine.
“Growing up in Rockford, Illinois, if you were smart and interested in biology, you were supposed to be a doctor,” he says.
Gillespie, meanwhile, was always more interested in primates. In seventh grade, he phoned animal psychologist Penny Patterson, famous for teaching the gorilla Koko how to use sign language, and interviewed the scientist about Koko’s diet while punching out notes on a typewriter. He was premed at the University of Illinois, but spent his internship at the Brookfield Zoo in Chicago, working in the “Tropic World” primate exhibit. His favorite undergrad course was biological anthropology, the study of biological and behavioral aspects of humans and nonhuman primates, looking at our closest relatives to better understand ourselves.
Gillespie eventually took a year off before graduate school to work with primate communities in the Peruvian Amazon. The apes finally won out — Gillespie would choose a doctorate in zoology
But it wasn’t long before the two fields of study collided. While monitoring the group behavior of colobine monkeys in Africa, Gillespie observed that some of the animals were eating bark from the African cherry tree — not a typical food source for them. When he dug deeper, Gillespie learned that human doctors in the region used that same bark to treat parasites in their patients. The monkeys, he realized, were self-medicating.
“That discovery in these monkeys brought me back toward the health science side of biology,” says Gillespie.