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article imageCan't quit smoking? Blame it on our Neanderthal ancestors

By Karen Graham     Jan 30, 2014 in Science
Homo sapiens and Neanderthals co-existed on earth for thousands of years. Then, about 30,000 years ago, the Neanderthals became extinct. Last year, a near-complete reconstruction of the Neanderthal genome was published, showing some interesting results.
Geneticists with the Harvard Medical School, researching the DNA of Neanderthal man have discovered that modern humans of non-African ancestry share about two to four percent of there genomes with Neanderthals.
It is believed that a small percentage of Europeans and Asians share a particular genetic code map, called a genome, that is a legacy passed down from the interbreeding of our early ancestors, homo sapiens, and Neanderthal man. These mutations are related to immune function and behavior traits, like the ability to stop smoking.
Professor David Reich, co-author of the research paper published in the journal Nature, had this to say about the importance of the findings, “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.”
Reich and his research partners at the Max Planck Institute for Evolutionary Anthropology in Germany, analysed the genetic make-up of 846 people with non-African ancestry, as well as 176 from sub-Saharan Africa and a toe bone from a 50,000 year old Neanderthal woman.
The group found that some areas of the genetic code map of people with non-African ancestry were rich with Neanderthal DNA, possibly necessary to survival of the species, while other areas were free of the same DNA. The areas of the genome without the DNA were in two parts of the code. One part is associated with the testes, the other with the X chromosome. Researchers believe this shows there was a high level of hybrid infertility present.
The genetic variations in those sharing Neanderthal DNA are important to the study of diseases linked to DNA heredity, especially in the study of auto-immune disorders. Research partner, Sriram Sankararaman, pointed out that 1,004 modern humans were studied, and the variations in the genetic make-up were more disposed toward the skin, nails and hair.
Neanderthal DNA  is found in regions of the genome affecting hair  skin and nails. This mutation was...
Neanderthal DNA is found in regions of the genome affecting hair, skin and nails. This mutation was needed for the survival of the species as we migrated toward the northerly regions of the world. The picture shows a group of Mountain Sami people in Lyngen, Troms in Norway.
T. Høegh
These mutations could have been a benefit to the survival of the hybrid humans carrying the DNA mix, as they further migrated into Eurasia and other parts of the world. But the most interesting variants found are associated with modern man's ailments, as well as the difficulty we have in our addiction to nicotine. A gene variant was found that is associated with the difficulty in trying to stop smoking. No, Neanderthals didn't smoke cigarettes, so more than likely, this particular mutation originally had another function.
There are a number of other disorders associated with the Neanderthal DNA variations, such as Type-2 diabetes, Lupus, billiary cirrhosis, Chrohn's disease, and long-term depression, to name a few. It is not known if Neanderthals suffered from these diseases or if these mutations affect only modern man when they are implanted into our genetic code. Sankararaman said: "We don't have the fine knowledge of the genetics of Neanderthals to answer this." He added that it was worth further study to find the answers.
In discussing the areas of modern man's genome that are devoid of Neanderthal DNA, it is evident that some genes had such bad affects on the interbreeding of the two species, they were flushed out through natural selection. This suggests that some individuals, the result of interbreeding, were sterile or had reduced fertility rates. Reich says, "It tells us that when Neanderthals and modern humans met and mixed, they were at the very edge of being biologically compatible."
There was another genome area devoid of Neanderthal DNA, called FOXP2. This region is believed to play a role in human speech. Further study is needed to understand how this barren area of the genome played a role in our heredity.
More about Dna, genetic varients, Mutations, Mating, Homo sapiens
 
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