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Agricultural Revolution Linked to Profound Changes in Human DNA

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Posted November 24, 2015

Without question, the Agricultural Revolution, which arrived in Europe around 8,500 years ago, was one of the most profound events in human history. Now, in the first study of its kind, an international group of geneticists have linked its coming with widespread DNA changes that altered people‘s height, digestion, immune system and skin colour.

As the supply of DNA from ancient skeletons increases, researchers are able to trace more and more of our evolutionary history. Image credit: Dave Hitchborne via geography.org.uk, CC BY-SA 2.0.

As the supply of DNA from ancient skeletons increases, researchers are able to trace more and more of our evolutionary history. Image credit: Dave Hitchborne via geography.org.uk, CC BY-SA 2.0.

David Reich, a geneticist at the Harvard Medical School, and his colleagues analysed the genomes of 230 people who lived between 8,500 and 2,300 years ago. The enormous sample size has provided enough data to track individual genetic variations as they became more or less common through the history of ancient Europe.

The remains that the group analysed span the entirety of Europe, and also include people from the Russian steppes, who swept into the continent around 4,500 years ago, and the inhabitants of Anatolia (Turkey), who brought farming to the Old World.

The analysis confirmed the hypothesis that Europeans became better able to digest milk after the introduction of farming, although this appears to have happened much later than was previously thought. The gene that aids in milk digestion, called LCT, dates back to only 4,000 years ago.

Reich’s group also found that early farmers developed a variant of the gene SLC22A4, which increases the absorption of ergothioneine – an amino acid lacking in wheat and other crops that became staples – thereby increasing the chances of survival among farmers who carried it.

This, however, brought its own problems – the same segment of DNA that carries SLC22A4 also contains a variation that raises the risk of digestive disorders like irritable bowel syndrome. These diseases, then, may be an indirect consequence of Europe’s pivot toward agriculture.

Another finding implicates farming in genetic mutations that led to the lightening of skin in most Europeans – a change more conducive to absorbing vitamin D from sunlight. Dr. Reich speculates that this was due to the new diet that turned from fish, rich in the vitamin, to grains that contain almost none of it.

Finally, the group traced the genes responsible for shorter stature in the south and higher in the north, although no explanation is currently available.

Reich and other researchers are now gathering more ancient European DNA to uncover further effects of natural selection. “I think in the future we can do this everywhere in the world, not just in Europe,” concluded Dr. Reich.

Sources: nytimes.com.

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