It’s 9 o’clock on a June morning in a muggy tropical forest not far from Brazil’s Atlantic coast and brown howler monkeys have been roaring for an hour. But the muriquis—the largest primates in the Americas after human beings, and the animals that the anthropologist Karen Strier and I have huffed uphill to see—are still curled high in the crooks of trees, waiting for the morning sun to warm them.
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As they begin to stir, the adults scratch, stretch and watch the suddenly frisky youngsters without moving much themselves. A few languidly grab leaves for breakfast. They are striking figures, with fur that varies between gray, light brown and russet. Their black faces inspired the Brazilian nickname “charcoal monkey,” after the sooty features of charcoal makers.
Strier knows these faces well. At age 54, the University of Wisconsin-Madison professor has been observing muriquis here for three decades. One of the longest-running studies of its kind, it has upended conventional wisdom about primates and may have a surprising thing or two to say about human nature.
“Louise!” Strier says, spotting one of her old familiars. Louise belongs to Strier’s original study group of 23—clássicos, Strier’s Brazilian students call them. “She’s the only female who’s never had a baby,” says Strier. “Her friends are some of the old girls.”
Above us, two youngsters frolic near their mother. “That’s Barbara,” says Strier, “and her 3-year-old twins Bamba and Beleco.” Female muriquis typically emigrate out of their natal group at about age 6, but Barbara has never left hers, the Matão study group, named after a valley that bisects this part of the forest. Even today, more than two years after I visited Brazil, Barbara remains in the group.
Strier first came to this federally protected reserve in 1982, at the invitation of Russell Mittermeier, now president of Conservation International and chairman of the primate specialist group of the International Union for Conservation of Nature’s Species Survival Commission, who had been conducting a survey of primates in eastern Brazil. The reserve at the time held only about 50 muriquis, and Strier, a Harvard graduate student, was smitten with the lanky creatures cavorting in the canopy.
“As soon as I saw the muriquis,” says Strier, “I said, ‘This is it.’” She stayed for two months and then returned for 14 more.
In those days, to reach this patch of forest she rode a bus almost 40 miles from the nearest town and walked the last mile to a simple house without electricity. Often alone, she rose before dawn to look for the monkeys and didn’t leave the forest until they had settled down at dusk. She cut her own network of footpaths, collecting data on births, relationships, diets, dispositions, daily locations and emigrations. At night, she sorted the data by the light of gas lanterns.
“As my contact with the animals increased, they introduced me to new species of food that they ate, and allowed me to witness new behaviors,” Strier wrote in her 1992 book Faces in the Forest, now a classic of primatology. As a personal account of a field biologist’s extraordinary, often lonely efforts to become acquainted with a wild primate, Strier’s work has been compared to Jane Goodall’s In the Shadow of Man and Dian Fossey’s Gorillas in the Mist.
When Strier was first getting to know the muriquis, primatology was still largely focused on just a handful of species that had adapted to life on the ground, including baboons, or that had close evolutionary relationships with humans, such as apes. This emphasis came to shape public perception of primates as essentially aggressive. We picture chest-beating, teeth-flashing dominant male gorillas competing to mate with any female they choose. We picture, as Goodall had witnessed beginning in 1974, chimpanzees invading other territories, biting and beating other chimps to death. Primates, including possibly the most violent one of all—us—seemed to be born ruffians.