WASHINGTON -- Chimpanzees and humans split from a common ancestor just 4 million years ago -- a much shorter time than current estimates of 5 million to 7 million years ago, according to a study published on Friday. The researchers compared the DNA of chimpanzees, humans and our next-closest ancestor, the gorilla, as well as orangutans. They used a well-known type of calculation that had not been previously applied to genetics to come up with their own"molecular clock" estimate of when humans became uniquely human."Assuming orangutan divergence 18 million years ago, speciation time of human and chimpanzee is consistently around 4 million years ago," they wrote in their study, published in the Public Library of Science journal PLoS Genetics.

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Genomic Relationships and Speciation Times of Human, Chimpanzee, and Gorilla Inferred from a Coalescent Hidden Markov Model