Diet and habitat have caused recent tweaks in human DNA

Scientists have spotted signs of recent evolution in the human genetic code, suggesting that diet and changes in habitat have had a lasting effect on our make-up.

In one of the first detailed scans of the entire human genome, researchers discovered more than 700 tweaks to genes they believe have arisen in the past 5,000 to 10,000 years, a period of time that saw humans spread north from equatorial regions and develop agriculture as a means of securing food.

As the fledgling human race encroached on new territories, shifts in climate and food saw that the best-adapted genes survived as less useful variations disappeared from the population.

Among the most striking changes are those in skin colour, with Europeans showing a surge in five genes linked to a lighter skin. At more northerly latitudes, where the sun's intensity is weaker, a lighter colour allows our skin to produce more vitamin D.

Moving north had other implications for our health. While the genetic code of the Africans tested revealed a gene that makes our bodies retain salt that would be lost through sweating, the Europeans and Asians had a version that causes more salt to be released, possibly acting as a defence against salt-induced hypertension (high blood pressure).

The study also reveals the emergence of a gene now found in 90% of Europeans that allows them to digest milk into adulthood, a likely consequence of dairy farming. The gene will probably be found in everyone in a further 1,000 years, the researchers say. Jonathan Pritchard, of the University of Chicago, examined data from 209 unrelated people from East Asia, Europe and Nigeria.

"There have been a lot of recent changes - the advent of agriculture, shifts in diet, new habitats, climatic conditions - over the past 10,000 years, and we're using these data to look for signs of very recent adaptation," Dr Pritchard said. His study appears in the online journal the Public Library of Science Biology today.