LOS ANGELES - DNA from a 40,000-year-old pinkie finger, belonging to a child and found in a cave in Siberia, indicates that it is from a previously unknown family of human relatives that lived among Neanderthals and modern humans, German researchers reported yesterday.
The discovery, if confirmed by research already under way, would mark the first time that an entirely new species of hominid has been identified solely on the basis of DNA sequencing, the team reported online in the journal Nature. It suggests that other unknown species could be similarly identified.
With the recent controversial discovery of the Hobbit-like species Homo floriensis that survived in Indonesia until 13,000 years ago, the evidence now indicates that at least four species of humanlike creatures walked the Earth at the same time.
The find suggests that "40,000 years ago, the planet was more crowded than we thought," wrote evolutionary biologist Terence A. Brown of the University of Manchester in an editorial accompanying the report.
The new species shared a common ancestor with both modern humans and Neanderthals about 1 million years ago, based on the DNA sequences, according to the team led by anthropologists Johannes Krause and Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig. That is about 500,000 years older than the last common ancestor shared by Neanderthals and modern humans.
"I like it because it makes us sort of a normal mammal," said anthropologist Todd R. Disotell of New York University's Center for the Study of Human Origins, who was not involved in the research. "We just happen to be the last one standing."
The DNA sequences are from mitochondria, tiny organelles within cells that provide power for all the activities of life. They thus provide a useful indicator of lineage, but say little about the physical characteristics of the whole organism.
The pinkie bone, from a child age 7 to 9, but of unknown gender, was found in 2008 in the Denisova Cave in the Altai Mountains of southern Siberia. DNA is preserved much better at such higher altitudes and in colder climates.
The cave shows signs of being occupied by humans and their relatives periodically for at least 125,000 years. The pinkie was found in a layer of soil dating from 48,000 to 30,000 years ago.