As a population of West African chimpanzees dwindles to critically endangered levels, scientists are calling for a definition of personhood that includes our close evolutionary cousins.

Just two decades ago, the Ivory Coast boasted a 10,000-strong chimpanzee population, accounting for half of the world's population. According to a new survey*, *that number has fallen to just a few thousand.

News of such a decline, published today in* Current Biology,* would be saddening in any species. But should we feel more concern for the chimpanzees than for another animal — as much concern, perhaps, as we might feel for other people?

"They are a people. Non-human, but definitely persons," said Deborah Fouts, co-director of the Chimpanzee and Human Communication Institute. "They haven't built a rocket ship to the moon. But we're not that different."

Fouts is one of a growing number of scientists and ethicists who believe that chimpanzees — as well as orangutans, bonobos and gorillas, a group colloquially known as great apes — ought to be considered people.

It's a controversial position. If being a person requires being human, then chimpanzees, our closest primate relative, are still only 98 percent complete. But if personhood is defined more broadly, chimpanzees may well qualify. They have self-awareness, feelings and high-level cognitive powers. Hardly a month seems to pass without researchers finding evidence of behavior thought to belong solely to humans.

Some even suggest that chimpanzees and other great apes should be granted human rights. So argued advocates for Hiasl, a chimpanzee caught in an Austrian custody battle, and the framers of an ape rights resolution passed by the Spanish parliament. The question of rights is practically thorny — how could a chimp be held responsible for, say, attacking another chimp? — but the fundamental question isn't practical, but rather scientific and ethical.

"They have been shown to have all kinds of complex communication and cognitive powers that are similar to humans," said Clayton State University primate researcher Jared Taglialatela. "They have feelings, they have ideas, they have goals."

The capacity of chimpanzees to feel, vividly illustrated when primatologist Jane Goodall documented the grief of a chimp named Flint

for his mother, is the least ambiguous of chimpanzee characteristics.

More ambiguous is their ability to think abstractly and empathically.

"They don't have time. They can't talk about yesterday or tomorrow.

Their communication is very much instantaneous: 'A neighbor is coming, let's go. A female's in heat, so check me out.' It's not, 'How are you today?'" said Pascal Gagneux, a University of California, San Diego primatologist. He considers chimpanzees to be persons, but fundamentally different from humans by virtue of their profoundly different communicative range.

But Fouts, who has trained her chimpanzees to use sign language, disagrees. "They do remember the past. When people come that they haven't seen in many years, they use their name signs," she said.

Taglialatela echoed Fouts. "I don't know if they think about what they want to be when they grow up," he said, "but they understand the concept that something will happen later."

Taglialatela has shown that chimpanzees utilize parts of their brain similar to our own Broca's and Wernicke's areas, which in humans are considered central to speech production and processing. When communicating, chimpanzees choose circumstance-appropriate forms:

gesturing by hand to someone who looks at them, or calling out to someone who looks away.

"We're seeing this rich communicative repertoire. It's not simply, 'I

see a piece of food and make some emotional sound,'" he said. "They're using different perspectives to communicate."

Researchers have also found that chimps use hand gestures that vary

according to context. The same gesture can be used for purposes as diverse as requesting sex or reconciling after a fight, a linguistic subtlety that suggests a capacity for high-level abstraction.

Chimpanzees even appear capable of altruism, being willing to help strangers in the absence of anticipated reward. But their empathy, said

Gagneux, who proposes treating research chimps in the manner of human subjects incapable of giving informed consent, does not translate to compassion.

Of course, compassion is hardly universal among humans. "How many times do you find yourself seeing someone on the news, or walking by someone on the street, and being apathetic towards them?" said Taglialatela.

And Fouts, who said that chimpanzees "feel pain and anger and love and affection and the kinds of feelings we feel," said that her sign language-trained chimpanzees can indeed inquire about the well-being of their handlers.

"They don't use it very often, but it doesn't mean they don't understand," she said.

So what of the situation in the Ivory Coast, where chimpanzee numbers have plummeted so dramatically that researchers say they're not merely endangered, but critically endangered? Should they be mourned as animals, or people?

Perhaps semantics are irrelevant.

"This is a tragedy, for lack of a better word," said Taglialatela.

Images: Linda Kenney / Buffa

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