Esta é uma nova espécie de ser humano?

sábado, março 27, 2010

Is this a new species of human being?

Scientists have extracted DNA from a bone discovered in Siberia that almost certainly belongs to a new kind of human – one that may have lived as recently as 30,000 years ago. Will this transform our views of human evolution?

The Guardian, Friday 26 March 2010
Article history

An artist's impression of the newly discovered 'fourth human' Photograph: Illustration: copyright Josie Jammet/Josie Jammet

From nothing more than a piece of bone from a child's little finger, the human family tree has gained another member, one who lived alongside modern humans perhaps as recently as 30,000 years ago.

Yesterday's revelation, that scientists in Germany had discovered – to their amazement – that the bone recovered from a cave in the mountains of southern Siberia almost certainly belonged to a new species of human, has sent ripples of excitement through academic circles. For the first time, the analysis of ancient DNA has rewritten the human story. Some 30,000 years ago, human life was far richer than we could have imagined.

Until recently, palaeontologists' view of human evolution was desperately lacking. Ask them to paint a picture of human existence 40,000 years ago, say, and they would mention modern humans, Homo sapiens, occupying vast territories. The only other hominid (a human or close relative) in existence back then, Homo neanderthalensis, was eking out a life alongside us modern humans, but its populations were in terminal decline. Then the Neanderthals became extinct around 25,000 years ago. That much was agreed upon.

Things changed in 2003. Field researchers working in caves on the Indonesian island of Flores uncovered remains of a diminutive human relative that lived at least 13,000 years ago. The Flores "hobbits" grew to be a metre tall as adults and could be traced back to Homo erectus, the forerunner of modern humans that left Africa 1.9m years ago. The hobbits' size is thought to be a direct result of their isolation.

Then there is the latest discovery, with which the number of early human species, or hominids, living 30,000 years ago has risen to four. In the space of a decade, the size of the human family has doubled.

And it's not just the cast list of the human evolution story that has had to be revised. Excavations of fossilised human remains have now led scientists to talk of three great migrations out of Africa. The first footprints leading off the continent were left by Homo erectus (the ancestor we share with the Neanderthals, with those hobbits, and with this new species of human). The next migration, around 450,000 years ago, was the Neanderthals. Then, perhaps as recently as 60,000 years ago, the first modern humans left to populate Eurasia and beyond – the humans from whom all of us alive on earth today are descended. The new species of human appears to fit in with none of these migrations out of Africa, and instead points to yet another great exodus, one that happened around 1m years ago.

To some scientists, even this fairly complicated picture is beginning to feel over-simplistic. "I don't think we can be absolutely certain about anything now," says Professor Terry Brown, an expert in ancient DNA at Manchester University.

What we do know is that the story starts in Africa, but that early humans then decided to leave. "There's no reason why a hominid should remain in Africa if the population increases," says Brown. "The natural thing for it to do is to move." The march out of the cradle of humanity may have been more of an ongoing wander, with early humans moving farther afield as and when they needed.
Read more here/Leia mais aqui: The Guardian