Neanderthals: our distant cousins … from 50,000 years ago

MOST of us have a Neanderthal side, thanks to some wayward behaviour by our distant ancestors, experts believe.

Scientists are convinced that early modern humans and Neanderthals interbred between 50,000 and 100,000 years ago.

Inter-human relations occurred as the first pioneering bands of Homo sapiens ventured out of Africa, scientists believe.

When they reached the Middle East they ran into groups of Neanderthals who preceded them. The rest, as they say, is history.

As a result, between 1 per cent and 4 per cent of the DNA of non-African people alive today is Neanderthal, according to the research.

The discovery emerged from the first attempt to map the complete Neanderthal genetic code, or genome. It more or less settles a long-standing academic debate over interbreeding between separate branches of the human family tree.

Evidence in the past has pointed both ways – for and against modern humans and Neanderthals having mixed their genes.

Technically the Neanderthals, Homo neanderthalensis, were a human sub-species that parted evolutionary company from our direct ancestors between 270,000 and 440,000 years ago.

About 400,000 years ago early Neanderthals stepped out of their African cradle, where Homo sapiens was still evolving, and headed for Europe and Asia.

At least 300,000 years later early modern humans followed the Neanderthals out of Africa. The two populations co-existed in Europe and Asia until the Neanderthals vanished for ever about 30,000 years ago – probably driven into extinction by the smarter and more competitive modern humans.

Previous genetic evidence has cast doubt on the likelihood of Homo sapiens and Neanderthals interbreeding. But this was based on analysis of a limited form of DNA locked in the mitochondria: bean-shaped energy-generating bodies in cells.

The new genome sequence published in the journal Science covers about 60 per cent of the whole Neanderthal genetic code, as imprinted in the chromosomes of cell nuclei. To highlight any differences, scientists compared the Neanderthal genome with those of present-day humans from southern and west Africa, China, Papua New Guinea and France.

They were surprised to find that Neanderthals were more closely related to modern humans from outside Africa than to Africans.

Even more mysteriously, the relationship extended to people from eastern Asia and the western Pacific – even though no Neanderthal remains have been found outside Europe and western Asia.

The most likely explanation is that Neanderthals and Homo sapiens interbred before early modern humans struck out east, taking traces of Neanderthal with them in their genes.

Professor Svante Paabo, director of evolutionary genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who led the international project, said: "Since we see this pattern in all people outside Africa, not just the region where Neanderthals existed, we speculate that this happened in some population of modern humans that then became the ancestors of all present-day non-Africans.

"The most plausible region is in the Middle East, where the first modern humans appeared before 100,000 years ago and where there were Neanderthals until at least 60,000 years ago.

"Modern humans that came out of Africa to colonise the rest of the world had to pass through that region."