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Scientists Discover Third Prehistoric Human Relative

View from a rock above Denisova cave on to the excavation field camp

View from a rock above Denisova cave on to the excavation field camp

Scientists have discovered a previously unknown prehistoric human relative to migrate out of Africa, in addition to Neanderthal and modern human ancestors. Researchers say they have a lot more to learn about the creature they call X-Woman.

X-Woman gets her name from a small, fossilized finger, possibly a pinky, found by anthropologists in 2008 in a cave in southern Siberia that contained prehistoric bracelets and other ornaments.

A preliminary genetic analysis of the 30,000 to 50,000 year old bone shows X-Woman represents a third wave of hominins that migrated out of Africa during the Ice Age, between homo erectus two million years ago, that gave rise to modern humans, and Neanderthal, which left the continent a half million years ago.

Svante Paabo is with the Max Planck Institute for Evolutionary Biology in Leipzig, Germany.

Paabo, who led the international researchers says a comparison of DNA with genetic material from anatomically modern humans and Neanderthal shows X-Woman descended from a common ancestor about a million years ago.

"So whoever sort of carried this mitochondrial genome after that, (we think) about a million years ago, is some new creature that has not been on our radar screen so far," Paabo said.

Fossil evidence of descendants of Neadrathal and modern human ancestors has also been found in the Siberian region near X-Woman, further supporting evidence that X-Women may turn out to be a previously undiscovered hominid species.

Scientists analyzed the fossil's mitochondrial DNA, primitive genetic material taken from subatomic particles called mitochondria, which provides energy for the cell.

Researchers are now conducting a fuller analysis of DNA extracted from the cell's nucleus which codes for the entire organism.

Paabo says that study will help scientists determine X-Woman's place on the human evolutionary tree. "We don't know if that person is a direct ancestor of us, for example," he said. "But by studying the nuclear genome we will be able to tell such things. Is it on the lineage to us? Is it on the lineage to the Neanderthal, or is it its own branch?"

A nuclear DNA analysis, according to Paabo, might even tell scientists whether X-Woman is a separate hominin species altogether.

The article by Svante Paabo and colleagues on the discovery of X-Women is published this week in the journal Nature.