Chimpanzees share 98 per cent of our DNA. But that does not mean they are close to being human. Sanjida O'Connell reports.

About 50 years ago something happened that radically changed our ideas about what it means to be human. A young secretary who had ventured into the African jungle witnessed a chimpanzee fashioning a tool out of a blade of grass and using it to fish for termites. Jane Goodall had been sent to Tanzania by Dr Louis Leakey, who, on hearing her startling news, came up with an equally startling statement: ''Now we must redefine 'tool', redefine 'man', or accept chimps as humans.''

In the 1960s Goodall, later founder of the Jane Goodall Institute, discovered more similarities between ourselves and chimpanzees: they can use stone tools; their mothers teach their infants; they feel similar emotions to us, such as fear, sadness and happiness, and they grieve over lost loved ones.

Subsequently, genetic research started to shore up her theory that ''the line between humans and other non-human beings, once thought so sharp, has become blurred''. Movements sprang up such as the Great Ape Project, founded in 1993 by the bioethicist Peter Singer, which argued that apes should be awarded some basic rights. And as genome mapping was developed, the genetic difference observed between humans and chimpanzees, our closest living ancestors, continued to shrink: it turned out that only 1.6 per cent of our genes were different.

This activity led to two conclusions: that humans and apes were not that different, and that if 98.4 per cent of our genes were shared with chimps, the remaining 1.6 per cent should explain why our development has differed so greatly from that of our cousins.

Yet a new book criticises both assumptions. ''Because we are virtually genetically identical, primatologists argue that in a logical sense, chimpanzees are very close to us cognitively,'' says Jeremy Taylor, author of Not a Chimp: The Hunt to Find the Genes that Make Us Human. ''The way this idea has bled into popular culture enrages me.''

Taylor is scathing on the subject of primate rights. ''I don't understand why conservation of the great apes has become synonymous with human rights and their similarity to us, whereas conservation of wetlands or a million other species doesn't carry any such conflations.'' In this he echoes geneticist Professor Steve Jones, who has argued that it is a mistake to apply a human concept, such as rights, to an animal. ''Chimpanzees share about 98 per cent of our DNA, but bananas share about 50 per cent, and we are not 98 per cent chimp or 50 per cent banana. We are entirely human and unique.''

Goodall's work was followed by a spate of studies demonstrating how close chimps' mental capacities seem to be to ours. They can, it is thought, show self-awareness, as demonstrated by what has become a classic test. Researchers put a blob of paint on a chimp's face without the animal noticing or being able to see the spot, and then give it a mirror. Macaques and other monkeys will react aggressively to their image, as if they are seeing another creature, whereas chimps will calmly sit down and rub the paint off.

In 1978 the scientists David Premack and Guy Woodruff published a paper asking if chimps had what they termed ''theory of mind'', the ability to understand that another being has thoughts, beliefs, desires and feelings. Because we have this ability, we think about what others are thinking; we don't treat others as if they were objects or automatons following a set of rules.

Most scientists working in this field would argue that chimps do not have the same capacity as humans for thinking about how others think, but that, nevertheless, chimps still have some understanding of mental states. ''It is time for humans to quit thinking that their nearest primate relatives only react to behaviour,'' says Dr Josep Call, of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who has been studying chimpanzees for many years. ''All the evidence suggests that chimpanzees understand both the goals and intentions of others as well as the perception and knowledge of others.'' Continued…

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