Gene data underline primate link

The Chimp: Our closest genetic relative

By BBC News Online science editor Dr David Whitehouse

Humans and chimpanzees are more closely related than we thought.

Scientists made the reassessment after studying 53 stretches of DNA scattered throughout the human genome, and comparing them with similar stretches in the genetic codes of a chimp, a gorilla and an orang-utan.

The research also suggests that the human line diverged from the chimp evolutionary line between 4.6 and 6.2 million years ago.

The research was carried out by Feng-Chi Chen of the National Tsing Hua University in Taiwan and Professor Wen-Hsiung Li of the University of Chicago, US.

The team looked at DNA from an Asian male that was not associated with active genes. After finding the equivalent sequences in other primates, the scientists looked for differences in the two codes.

The researchers discovered that human and chimp DNA differs by just 1.24%, half a per cent less than had been thought. Humans differ from gorillas by 1.62% and from orang-utans by 1.63%, again less than had been believed.

The genetic differences studied by the researchers arise through mutation - they are errors that creep into the code as it is copied. Because these errors occur, on average, at a steady rate, they can be used to "look back" in genetic history and provide an estimate of how long ago the primates diverged into separate species.

Orang-utans were the first to separate, between 12 and 16 million years ago; gorillas between 6.2 and 8.4 million years ago and finally humans and chimps went their different ways between 4.6 and 6.2 million years ago.