Genes Reveal Mysterious Group of Hominids as Neandertal Relatives: DNA Analysis Suggests Interbreeding with Modern Humans
Sanders, Laura, Science News
Neandertals need to make room for a new member 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 a distinct group of early hominids living in central Asia about 40,000 years ago was closely related to the Neandertals. Data from the finger and a molar tooth found in the cave also show that, like Neandertals, the mysterious group interbred with modern humans, in this case leaving behind a genetic legacy in modern-day Melanesians of Papua New Guinea and Bougainville Island.
Reported December 23 in Nature, the work 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, who was not involved in the research. "We're just scraping the outside of what's probably a much more complex picture."
Even 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.
The presence of the ancient group's genes in modern-day humans suggests that it 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 coauthor David Reich of the Broad Institute of MIT and Harvard in Cambridge, Mass. "Now there's a third group that's neither Neandertal nor modern human."
He and his colleagues call the group "Denisovans," after the Denisova Cave in southern Siberia where the finger bone and tooth were found.
Last year, researchers studied the mitochondrial DNA from the finger bone (SN: 4/24/10, p. 5), leading them to conclude that the girl belonged to a group that split from the line leading to modern humans roughly a million years ago, well before the Neandertal-human split about 270,000 to 440,000 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 catalog the finger's nuclear DNA. …