• Discovery was made after DNA analysis on a Neanderthal woman's toe bone
  • Her mother and father were closely related and may have been half-siblings
  • Inbreeding may have been result of Neanderthal population being very small
  • Scientists say many people alive today still carry ancient Neanderthal genes
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The toe bone of a Neanderthal woman, recovered from a cave in Siberia. 50,000 year-old DNA extracted from the bone was used to produce the most complete sequence so far of the genome of this group of early humans
Neanderthals liked to be close to their families - very close, a genetic study has shown.

DNA from a Neanderthal woman's 50,000-year-old toe bone shows she was highly inbred.

Scientists discovered that her parents were either half-siblings who shared the same mother, an uncle and niece, an aunt and nephew, or a grandparent and grandchild.

Alternatively, they may have been double first cousins - offspring of two siblings and their siblings.

The inbreeding may have been the result of Neanderthal population groups being very small, experts believe.

Analysis of the DNA also revealed evidence of interbreeding between Neanderthals, Denisovans - a Neanderthal sister group from Siberia - and early modern humans.

Neanderthals were a human sub-species who lived alongside our own ancestors in Eurasia for thousands of years before vanishing about 30,000 years ago.

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Scientists discovered that the Neanderthal's parents were either half-siblings who shared the same mother, an uncle and niece, an aunt and nephew, or a grandparent and grandchild
Although like early modern humans they made tools and weapons, their lack of inventiveness and social structure may have led to their demise.

For many years scientists argued about whether Neanderthals and modern humans ever interbred. DNA studies have now proved that they did, and many people alive today still carry ancient Neanderthal genes.
The new findings, published in the journal Nature, come from the most complete blueprint of a Neanderthal genetic code, or genome, ever constructed.

Scientists sequenced the genome from DNA extracted from the toe bone of a Neanderthal woman whose remains were found in a Siberian cave in the Altai Mountains.

Comparing it with the genomes of modern humans and Denisovans revealed some surprises.

Neanderthals and Denisovans were found to be closely related, parting company on the evolutionary path 300,000 years ago. More than 100,000 years earlier, they and modern humans had a common ancestor.

The evidence of inbreeding was uncovered by an analysis led by Dr Montgomery Slatkin, a population geneticist at the University of California.

'We performed simulations of several inbreeding scenarios and discovered that the parents of this Neanderthal individual were either half siblings who had a mother in common, double first cousins, an uncle and a niece, an aunt and a nephew, a grandfather and a granddaughter, or a grandmother and a grandson,' he said.

The scientists estimated that between 1.5 per cent and 2.1 per cent of the genomes of modern non-African people can be traced to Neanderthals.

Denisovans are also believed to have left their genetic traces, though only in some Oceanic and Asian populations.

The study also identified at least 87 specific genes in modern humans that stand out as significantly different from any found in Neanderthals or Denisovans.

They may hold clues to why the Neanderthals and Denisovans died out while modern humans survived.

The list of genes contains a 'catalogue' of features setting modern humans apart from all other creatures, living or extinct, according to Dr Svante Paabo, from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who led the international team.

'I believe that in it hide some of the things that made the enormous expansion of human populations and human culture and technology in the last 100,000 years possible,' he said.

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Scientists sequenced the genome from DNA extracted from the toe bone of a Neanderthal woman whose remains were found in a Siberian cave in the Altai Mountains

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Denisova Cave in the Altai Mountains of southern Siberia. At various times over the past 50,000 years, three different groups of early humans - Neanderthals, Denisovans and modern humans - lived in the cave
In addition the genome comparisons showed that Denisovans bred with a fourth group of humans living in Eurasia that had an ancestry dating back more than a million years.

The scientists believe this mysterious relation may have been Homo erectus, which fossils show inhabited Europe and Asia at least a million years ago.

'The paper really shows that the history of humans and hominins during this period was very complicated,' said Prof Slatkin.

'There was lot of interbreeding that we know about and probably other interbreeding we haven't yet discovered.'

Professor Chris Stringer, a leading expert in human origins at London's Natural History Museum, said the inbreeding disclosed by the Neanderthal woman's DNA must have gone on 'for a number of generations'.

He added: 'Despite the fact that her ancestors had ranged widely in Eurasia for tens of millennia, her genomic diversity was less than that found in a small population of hunter-gatherers living in the Amazonian rainforest today.

'This suggests that the historical population sizes of both Denisovans and Neanderthals in Eurasia were much lower than those maintained by ancestral modern humans in Africa.'
THE DNA EVIDENCE OF NEANDERTHAL INBREEDING

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The evidence of inbreeding was uncovered by an analysis led by Dr Montgomery Slatkin, a population geneticist at the University of California.

His team sequenced the genome from DNA extracted from the toe bone of a Neanderthal woman whose remains were found in a Siberian cave in the Altai Mountains.

'We performed simulations of several inbreeding scenarios and discovered that the parents of this Neanderthal individual were either half siblings who had a mother in common, double first cousins, an uncle and a niece, an aunt and a nephew, a grandfather and a granddaughter, or a grandmother and a grandson,' he said.

Neanderthals and Denisovans were found to be closely related, parting company on the evolutionary path 300,000 years ago. More than 100,000 years earlier, they and modern humans had a common ancestor.

The scientists estimated that between 1.5 per cent and 2.1 per cent of the genomes of modern non-African people can be traced to Neanderthals.