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The Forgotten Ape Why can't the gibbon get any respect?

By Ben CrairPosted Tuesday, July 29, 2008, at 4:20 PM ET

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William Saletan examined the Spanish ape-rights bill and concluded that animal equality is a myth. Peter Singer and Richard A. Posner debated animal rights in 2001. Torie Bosch wondered whether we could ever produce a half-human, half-gorilla baby, and Daniel Engber explained how to teach sign language to a gorilla. Alex Abramovich analyzed the radical political history of Planet of the Apes. (David Edelstein didn't much care for Tim Burton's 2001 remake of the film.) In 1997, Sarah Kerr reviewed Will Self's novel, Great Apes.

Scientists haven't proven gibbons deficient so much as they haven't bothered looking. The few who have relate encouraging results: Thomas Geissmann, director of the Gibbon Research Lab in Zurich, has observed mirror self-recognition in gibbons, which is generally regarded as a sign of self-awareness; others have observed tool use by gibbons in captivity. Alan Mootnick says he's met a gibbon capable of rudimentary sign language and suggests that gibbons may have more difficulty signing than the great apes because of the unique morphology of their hands—which are equal in length to human hands but half the width. However, all of these observations are anecdotal; high-level cognition in gibbons has not been systematically studied.

Meanwhile, there are whole institutes devoted to the study of the cognitive abilities of great apes. And many of their vaunted discoveries have come only after long and arduous work. For example, gorillas are often celebrated for their ability to recognize themselves in a mirror, but the earliest studies found just the opposite. Scientists began testing for self-recognition in gorillas in 1981 but did not find it until 10 years later. Koko, a research animal in California (and an alleged nipple fetishist), was able to identify her reflection. But she was a very special case: Humans had reared her since the age of 1. Some researchers are skeptical of mirror self-recognition in gorillas, but they have no problem rationalizing its absence, suggesting that the gorillas' aversion to eye contact might prevent them from looking in the mirror long enough. Gibbons have not had the benefit of such attention and large sample sizes. "In the initial studies, they just tested one or two gibbons and said, 'Oh yeah, they failed,' " says Geissmann.

Tests of animal self-recognition sometimes seem more like exercises in human self-recognition: Gorillas appear humanlike, so we test them repeatedly until we can prove they have some form of consciousness. Gibbons, on the other hand, look like monkeys, so we're inclined to dismiss them as "lesser" without a second thought. While it's true that the great apes are more closely related to each other than they are to gibbons, it's also true that the gibbons are more closely related to the great apes, including humans, than they are to any monkey.

As a result, interesting aspects of gibbon ethology have long been ignored. The lesser apes, for example, are the only apes besides humans to live in monogamous couples. Among the apes, their songs are second in acoustic sophistication only to humans', and they walk bipedally when grounded, unlike the great (nonhuman) apes. But it's hard to generate interest in the lesser apes, especially given that no charismatic human researcher—à la Goodall or Fossey—has ever taken up their cause.

What makes this particularly frustrating is that the most endangered species of ape isn't a gorilla, chimpanzee, or orangutan. Certain types of gibbon are in far greater trouble. The orangutan may be the beneficiary of a high-profile conservation campaign in Indonesia, but it's not as rare as the Javan gibbon. In four decades, the western hoolock gibbon has declined in number from 100,000 to just 5,000. The Hainan gibbon, of which only 20 or so individuals survive, is perhaps the most endangered primate in the world. The eastern black-gibbon population in Vietnam has similarly dwindled to a few dozen.

Such species are unlikely to survive as long as humans treat gibbons as second-rate apes. Recently, there have been some encouraging signs: Legislation introduced in the U.S. House of Representatives would prohibit laboratory testing on all apes, including gibbons. This wouldn't have much of a direct impact since small apes are rarely studied in labs. But it would have symbolic importance. The petite, tree-dwelling gibbon may not be as easily anthropomorphized as its great ape cousins, but that's no reason to ignore it. In protecting the great apes, the Spaniards overlooked at least one vital human right: Freedom from discrimination based on appearance or lifestyle.