X Woman

No, not a superhero, but a newly found cousin.

To the trained eye of the palaeontologist, the tiny fragment of fossilised bone can be identified as coming from the little finger of a child who lived about 40,000 years ago in the Altai mountains of southern Siberia. But in the hands of molecular biologists, the bone has revealed that it belonged to a new lineage of human being, an unknown "hominin" who, although human, was not a member of our own species, Homo sapiens.

The finger-bone was unearthed in 2008 from the floor of Denisova Cave, a rock shelter known to have been inhabited by ancient humans for several hundred thousand years. Now, after exhaustive tests on DNA extracted from the fragment, scientists can reveal that in Siberia at this time there lived a hitherto unknown type of human who was neither Homo sapiens nor Neanderthal, the only other human species living in the area at about this time.

It raises the intriguing possibility that in this part of central Asia about 40,000 years ago three species of human were living alongside one another, perhaps for thousands of years. Nothing is known of how they interacted or whether they interbred but it is clear that only one of the three species survived, anatomically modern humans.

The universe is an amazing place.