Humanity’s pedestal lowered again?

People and chimpanzees share an even closer genetic kinship than is usually assumed, according to a new study. So close is the connection that living chimp species belong to the genus Homo, just as people do, contend Morris Goodman of Wayne State University in Detroit and his colleagues. Until now, chimps have been classified in a separate genus, Pan.

Genetic analyses also indicate that all living apes–chimps, gorillas, and orangutans–belong to the evolutionary family known as hominids, Goodman’s group claims in the June 10 Proceedings of the National Academy of Sciences. Researchers traditionally have regarded hominids as a group consisting only of people and our prehistoric ancestors who originated at least 5 million years ago.

From a genetic perspective, “humans appear as only slightly remodeled chimpanzee-like apes,” the scientists contend.

Goodman and his colleagues focused on so-called functional DNA mutations known to alter protein production in favorable ways and thus likely to have been preserved through natural selection. Sequences of DNA components from 97 human genes were compared with corresponding chimp DNA sequences and with available sequences from gorillas, orangutans, Old World monkeys, and mice.

People and chimps exhibited the closest genetic relationship, sharing 99.4 percent of the sequences at functional mutation sites. The scientists estimate that a common ancestor of chimps and people lived between 5 million and 6 million years ago. Living chimps have diverged genetically from that common ancestor about as far as people have, the researchers add.

Goodman’s controversial theory also folds other ancient apelike ancestors into the Homo lineage, including the 3-million- to 4-million-year-old genus Australopithecus.

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