If chimpanzees truly followed what humans call the law of the jungle, a mentally disabled chimp named Knuckles would never stand a chance.
Yet Knuckles has found acceptance and perhaps even sympathy from his fellow chimps in Florida, making him an unlikely star of Lincoln Park Zoo's international Mind of the Chimpanzee conference.
The meeting, which runs Friday through Sunday with 300 researchers from around the world, is billed as the first major conference devoted to chimp cognition, and the first academic chimp conference at the zoo since 1991.
Although much of the meeting will examine the impressive intelligence of humanity's closest living relatives, Knuckles offers unique insight as the only known captive chimp with cerebral palsy, which immobilized one arm and left him mentally unable to follow the intricate protocols of chimp society.
Normally, older chimps would put on intimidating displays with a juvenile male such as Knuckles, screaming, grabbing and biting the youngster to put him in his place, said Devyn Carter, who has studied Knuckles and is presenting his research at the Lincoln Park Zoo conference. But even the dominant alpha male tolerates and gently grooms Knuckles.
"To my knowledge he's never received a scratch," said Carter, a research assistant at Emory University's Yerkes National Primate Research Center. "They seem to sense somehow that he's different."
Such behavior touches on a central theme of many presentations at the Lincoln Park Zoo conference: How well do chimps understand what other chimps know, feel and perceive?
Some experts believe chimps and other higher primates have genuine empathy, the ability to imagine themselves in another animal's place. And that may be the first step in the evolution of morality.
Chimps may use their empathic skills for good, but also to manipulate others. Researchers have found that chimps have a talent for deception, which requires mental sophistication, said conference co-organizer Elizabeth Lonsdorf, director of the zoo's Lester E. Fisher Center for the Study and Conservation of Apes.
"Lying and deceiving means you have to know what another individual thinks is the truth, and act in such a way to work around that truth," Lonsdorf said. "It takes complex information processing."