DETROIT, July 7: Chimpanzees are so like us they should be considered another branch of the human family, scientists say.

At present only human beings belong to the genus Homo, setting them apart from the great apes and all other animals. But a new analysis of genetic similarities between chimps and humans now suggests that both should be classified in the same taxonomic group.

Morris Goodman and colleagues from the Wayne State University School of Medicine in Detroit, compared 97 genes from six different species — humans, chimpanzees, gorillas, orang-utans, Old World monkeys and mice.

The scientists then constructed an evolutionary tree that measured the degree of relatedness between the six species. According to their analysis, chimpanzees and humans occupy sister branches on the family tree, with a genetic similarity of 99.4 per cent. Next on the tree were gorillas, followed by orang-utans and Old World monkeys.

Mice were only included in the analysis to provide a benchmark comparison with an unrelated species. By tracking the mutation rates in each animal’s genes, the researchers estimated that humans and chimpanzees diverged from a common ancestor about five or six million years ago. The common ancestor had, in turn, diverged from gorillas about six to seven million years ago.

Writing in the journal “Proceedings of the National Academy of Sciences”, the researchers suggested that all present day apes should be broadly classified as Hominidae. However, humans and chimpanzees should belong to the same narrower genus of Homo.

The scientists wrote: “The nearly finalised complete genomic DNA sequence representing humans and the mounting DNA sequence data for other primates (now growing most rapidly for chimpanzees) are making possible a comprehensive genome-wide genetic analysis of the place of humans in evolution.—dpa