Meet the Chimps That Lawyers Argue Are People

In a new study, chimpanzees were trained to walk upright. The fine print: They’re also plaintiffs in a landmark lawsuit.   

The plaintiffs of a historic lawsuit seeking legal rights for chimpanzees finally made a public appearance—not in court, but in a study on the mechanics of walking on two feet.

The study, published Tuesday in the journal Nature Communications, describes how two chimps trained to walk upright move more like humans than expected, perhaps hinting at the evolutionary origins of our own gait.

It hints at so much more. The research was conducted on Hercules and Leo, two 7-year-old chimps kept at the Stony Brook University laboratory of anthropologist Susan Larson. Earlier this summer, these two chimps received worldwide attention when activists with the Nonhuman Rights Project argued in a New York courtroom that Leo and Hercules should legally be considered people with a right to be free.

Absent from those proceedings were Hercules and Leo themselves. News stories about the lawsuit—eventually dismissed, currently being appealed—were illustrated with stock chimpanzee photographs. A video accompanying the new study is the first chance most people will have to see the chimps, and their appearance raises anew the question: Is a chimpanzee a person?

It depends on who you talk to. If person is synonymous with human, then Homo sapiens' closest living relative is by definition not one. But if—in a philosophical rather than legal context—being a person means possessing traits considered fundamental to human experience, several lines of scientific evidence suggest chimps fit the bill.

What's a Person?

Many hundreds of studies describe the richness of chimpanzee cognition, emotion, communication, and social life. "If we think of 'persons' as autonomous individuals who can remember, plan, and act on those plans, we are certainly not talking about only 'human' characteristics," says Catherine Hobaiter, a University of St. Andrews primatologist who has translated chimp gestures.

By this standard, chimps' inner lives are not identical to ours, but close enough for them to qualify as people. Whether that should apply in legal contexts, where 'person' is a term designating an entity capable of having rights, is controversial.  

At present, only humans and our constructs, such as corporations or ships, are legal persons. To Nonhuman Rights Project founder Steve Wise, this is an oversight: Personhood isn't rooted in species membership, but respect for an individual's ability to make meaningful choices—or, in a word, their liberty.

Others, including Pepperdine University scholar Richard Cupp and the judge in another Nonhuman Rights Project lawsuit, say personhood is contingent on fulfilling social responsibilities. Chimps ostensibly cannot.

Hobaiter believes chimps—and many other species—should have some legal rights, including the right not to be held captive for human benefit. By contrast, Steve Ross, director of the Center for the Study and Conservation of Apes at Chicago's Lincoln Park Zoo, philosophically considers chimps to be people but doesn't quite support legal rights.

"Where it gets difficult is going from the broad philosophical definitions into the legal ramifications," says Ross, who prefers to pursue other means of helping chimps. He chairs the Chimp Haven sanctuary's board and pushed for a recent U.S. Fish and Wildlife Department rule that classified captive chimps as endangered, effectively ending invasive medical research on 700 chimps still living in U.S. labs.

(Watch: former lab chimps retire to Chimp Haven.)

Research with Hercules and Leo has reportedly concluded, with the pair scheduled for transfer to a sanctuary. Regardless of whether they're considered people, Ross argues, those chimps had a hard life.

The pair arrived at Stony Brook as near-infants in 2010. In the wild, says Ross, they would have spent the years since in near-constant contact with their mothers. Instead they lived indoors, with only each other and researchers for company.

"They were given attention," Ross says, "but that's not going to override the damage done from maternal separation."