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| Neanderthals gave us disease genes | Neanderthals gave us disease genes |
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| Genes that cause disease in people today were picked up through interbreeding with Neanderthals, a major study in Nature journal suggests. | Genes that cause disease in people today were picked up through interbreeding with Neanderthals, a major study in Nature journal suggests. |
| They passed on genes involved in type 2 diabetes, Crohn's disease and - curiously - smoking addiction. | They passed on genes involved in type 2 diabetes, Crohn's disease and - curiously - smoking addiction. |
| Genome studies reveal that our species (Homo sapiens) mated with Neanderthals shortly after leaving Africa. | Genome studies reveal that our species (Homo sapiens) mated with Neanderthals shortly after leaving Africa. |
| But it was previously unclear what this Neanderthal DNA did and whether there were any implications for human health. | But it was previously unclear what this Neanderthal DNA did and whether there were any implications for human health. |
| Between 2% and 4% of the genetic blueprint of present-day non-Africans came from Neanderthals. | Between 2% and 4% of the genetic blueprint of present-day non-Africans came from Neanderthals. |
| By screening the genomes of 1,004 modern humans, Sriram Sankararaman and his colleagues identified regions bearing the Neanderthal versions of different genes. | By screening the genomes of 1,004 modern humans, Sriram Sankararaman and his colleagues identified regions bearing the Neanderthal versions of different genes. |
| That a gene variant associated with the inability to stop smoking should be found to be of Neanderthal origin is a surprise. | That a gene variant associated with the inability to stop smoking should be found to be of Neanderthal origin is a surprise. |
| The researchers are, of course, not suggesting that our evolutionary cousins were puffing away in their caves. | The researchers are, of course, not suggesting that our evolutionary cousins were puffing away in their caves. |
| Instead, they argue, this gene may have more than one function; the modern effect of this genetic marker on smoking behaviour may be one impact among several. | Instead, they argue, this gene may have more than one function; the modern effect of this genetic marker on smoking behaviour may be one impact among several. |
| Pastures new | Pastures new |
| When the two populations met, the Neanderthals had already been adapting to the cooler Eurasian environment for several hundred thousand years. Researchers have found that Neanderthal DNA is not distributed uniformly across the human genome, instead being commonly found in regions that affect skin and hair. | When the two populations met, the Neanderthals had already been adapting to the cooler Eurasian environment for several hundred thousand years. Researchers have found that Neanderthal DNA is not distributed uniformly across the human genome, instead being commonly found in regions that affect skin and hair. |
| These include parts of the genome linked to the regulation of skin pigmentation, suggesting our ancient relatives may have passed on characteristics - such as paler skin - that helped modern humans adapt to the reduced sunlight they encountered when moving into more northerly climes. | These include parts of the genome linked to the regulation of skin pigmentation, suggesting our ancient relatives may have passed on characteristics - such as paler skin - that helped modern humans adapt to the reduced sunlight they encountered when moving into more northerly climes. |
| "We found evidence that Neanderthal skin genes made Europeans and East Asians more evolutionarily fit," said Benjamin Vernot, co-author of a separate study in Science journal. | "We found evidence that Neanderthal skin genes made Europeans and East Asians more evolutionarily fit," said Benjamin Vernot, co-author of a separate study in Science journal. |
| Genes for keratin filaments, a fibrous protein that lends toughness to skin, hair and nails, were also enriched with Neanderthal DNA. This may have helped provide the newcomers with thicker insulation against cold conditions, the scientists suggest. | Genes for keratin filaments, a fibrous protein that lends toughness to skin, hair and nails, were also enriched with Neanderthal DNA. This may have helped provide the newcomers with thicker insulation against cold conditions, the scientists suggest. |
| "It's tempting to think that Neanderthals were already adapted to the non-African environment and provided this genetic benefit to (modern) humans," said Prof David Reich, from Harvard Medical School, co-author of the paper in Nature. | "It's tempting to think that Neanderthals were already adapted to the non-African environment and provided this genetic benefit to (modern) humans," said Prof David Reich, from Harvard Medical School, co-author of the paper in Nature. |
| But other genes are implicated in human illnesses, especially autoimmune disorders. Disease causing gene variants include those linked to type 2 diabetes, long-term depression, lupus, billiary cirrhosis - an autoimmune disease of the liver - and Crohn's disease. | But other genes are implicated in human illnesses, especially autoimmune disorders. Disease causing gene variants include those linked to type 2 diabetes, long-term depression, lupus, billiary cirrhosis - an autoimmune disease of the liver - and Crohn's disease. |
| "Now that we can estimate the probability that a particular genetic variant arose from Neanderthals, we can begin to understand how that inherited DNA affects us," said Prof Reich. | "Now that we can estimate the probability that a particular genetic variant arose from Neanderthals, we can begin to understand how that inherited DNA affects us," said Prof Reich. |
| "We may also learn more about what Neanderthals themselves were like." | "We may also learn more about what Neanderthals themselves were like." |
| Neanderthal 'deserts' | Neanderthal 'deserts' |
| However, some regions of the genome were discovered to be devoid of Neanderthal DNA, suggesting that certain genes had harmful effects in the offspring of modern human-Neanderthal pairings. | However, some regions of the genome were discovered to be devoid of Neanderthal DNA, suggesting that certain genes had harmful effects in the offspring of modern human-Neanderthal pairings. |
| "We find that there are large regions of the genome where most modern humans carry little or no Neanderthal ancestry," Mr Sankararaman told BBC News. | "We find that there are large regions of the genome where most modern humans carry little or no Neanderthal ancestry," Mr Sankararaman told BBC News. |
| "This reduction in Neanderthal ancestry was probably due to selection against genes that were bad - deleterious - for us." | "This reduction in Neanderthal ancestry was probably due to selection against genes that were bad - deleterious - for us." |
| The implication is that there was active removal of Neanderthal genes from parts of the genome over the course of evolution. | |
| The Neanderthal-deficient regions encompass genes that are specifically expressed in the testes, and on the X (female sex) chromosome. | The Neanderthal-deficient regions encompass genes that are specifically expressed in the testes, and on the X (female sex) chromosome. |
| This suggests that some Neanderthal-modern human hybrids had reduced fertility and in some cases were sterile. | |
| "It tells us that when Neanderthals and modern humans met and mixed, they were at the very edge of being biological compatible," said Prof Reich. | |
| Paul.Rincon-INTERNET@bbc.co.uk and follow me on Twitter | Paul.Rincon-INTERNET@bbc.co.uk and follow me on Twitter |