A mere 1% difference in DNA separates humans from our closest living relatives - the chimpanzees. The “Great Ape Project” argues that because the differences between humans and other great apes (chimpanzees, bonobos, gorillas and orangutans) are so slight the Great Apes should share basic human rights. The Project aims to have the UN adopt a declaration on the rights of nonhuman apes that would make research on them impossible.
Supporters of the Great Ape Project point to the psychological similarity between nonhuman apes and ourselves: nonhuman apes, they argue, are self-aware. As a consequence of self-awareness great apes must suffer in captivity in ways similar to what we would experience.
This is no abstract debate. There are about 1,600 chimpanzees held for biomedical research in the US alone and are central to the study of several maladies. Perhaps the most important example is liver disease. Research on chimpanzees led to the vaccine against hepatitis B. Nearly half the global population is at high risk of contracting this virus. Chimpanzees have also been crucial for the study of hepatitis C.
But hepatitis only heads the list. AIDS is another example, because chimpanzees are the only nonhuman species that can be infected with HIV. Chimpanzees are also helping scientists battle other health problems, including spongiform encephalitis (“mad-cow disease”), malaria, cystic fibrosis and emphysema. Because they are close to us, nonhuman great apes are suitable for research on several diseases that cause human suffering. Yet, does this similarity make biomedical experimentation difficult to justify ethically?
One reason to think so is the idea that the minds of nonhuman great apes are similar to ours because some of animals have been taught sign language. But thirty years of research on the abilities of chimpanzees and bonobos to communicate using signs has demonstrated few compelling examples of anything close to human language. In all these studies, the animal’s vocabulary developed slowly, and never exceeded a couple of hundred signs (about two weeks’ work for a healthy two-year-old child). Chimpanzee utterances rarely extend beyond one or two signs – making discussion of grammar or syntax forced.
More recent reports suggesting ape grammar are those of a bonobo named Kanzi, whose linguistic abilities are alleged to exceed those seen in earlier sign-language studies with chimpanzees. A critical test for Kanzi’s comprehension of sentence structure involved asking him to respond to an instruction such as “would you please carry the straw?” Sure enough, Kanzi picks up the straw. But although grammar may have conveyed the correct meaning of the test sentence, the circumstances could also have made the requested action obvious (given that Kanzi knows what the words