A team of international researchers led by Harvard Medical School has presented an in-depth study of the changes that occurred in the human genome on the arrival of agriculture and farming. The scientists compared the current human genomes with ancient DNA and found genetic differences attributed to natural selection in the face of the environmental changes that took place 8500 years ago. The findings were published in the journal Nature.
The recent improvements in DNA extraction techniques have made possible to collect ancient DNA samples of a quality that allows accurate sequencing. As an example, one of these techniques allows to extract huge amounts of DNA from an auditory organ bone. In one year, the number of available genomic scale samples increased from 10 to 230. The researchers could compare a large collection of DNA samples from hunter-gatherers with others dating from the transition to farming societies, and also with current genomes, covering genetic changes that happened before, during and after the agricultural revolution.
Changes in genes related to diet and immunity
Most changes happened in genes -or close to genes- related to height, pigmentation, eye color, fatty acid metabolism, lactose digestion and immunity. These changes are directly related to changes in diet, climate (due to migration) and population density (immunity was selected when living close to animals and other humans). The results are not surprising, but are a confirmation of what had been speculated for a long time, and another irrefutable evidence of natural selection.
The researchers tried also to evaluate genomic changes other than the ones related to diet, pigmentation, and immunity, but could not find clear adaptations to possible environmental pressures.
The study also demonstrates that Europe´s first farmers migrated from Anatolia (currently Turkey). This opens the door to the use of the currently available DNA extraction techniques and genome-sized ancient DNA samples to better understand population migrations and environmental adaptations throughout prehistory and history.