Neanderthal Relative Bred With Humans

A previously unknown Siberian group, the Denisovans, left fingerprints in some humans' DNA.

Neanderthals need to make room for a new kid sister in the early human family.

By sequencing the full genome of a girl's fossil finger bone found in a Siberian cave, researchers conclude that there must have been a closely related sister group of Neanderthals living in central Asia about 40,000 years ago. The data also show that, like Neanderthals, the mysterious group interbred with modern humans, in this case leaving behind a genetic fingerprint in modern-day Melanesians of Papua New Guinea and Bougainville Island, nearly 10,000 kilometers (6,213 miles) from where the fossil was found.

The new genetic information, reported Dec. 23 in Nature, underscores the fluidity of human evolution and hints that even more groups are waiting to be uncovered, says paleoanthropologist Milford Wolpoff of the University of Michigan in Ann Arbor. "We're just scraping the outside of what's probably a much more complex picture."

As recently as a year ago, evidence suggested that modern humans spread throughout the world in a single migration out of Africa that wiped out any genetic traces of other early hominids. But the new study suggests that the lineage of modern humans is much more intertwined.

"This is quite exciting," says genomicist Webb Miller of Pennsylvania State University in University Park. "A lot of people are going to hate it and a lot of people are going to love it."

The presence of the ancient group's genes in modern-day humans suggests that the new group, christened "Denisovans" after the Denisova Cave in southern Siberia where the finger bone was found, was once widespread throughout Asia.

"This was a place where Neandertals and modern humans were already known to be living, right in this region," says study co-author David Reich of the Broad Institute of MIT and Harvard in Cambridge, Mass. "Now there's a third group that's neither Neanderthal nor modern human."

Earlier this year, researchers reported sequencing the mitochondrial DNA from the finger bone, leading them to conclude that the girl belonged to a new group that split from the line leading to modern humans about a million years ago, before the Neanderthal-human split about 270,000 to 400,000 years ago. But mitochondrial DNA, a small loop of genetic material inherited only through the female line, isn't as informative as the DNA packed into cells' nuclei. So Reich and his colleagues decided to sequence the entire nuclear genome.

Read more at Discovery News