New analysis from ancient DNA of archaeological skeletons shows that Europeans had darker skin, hair, and eye pigmentation 5,000 years ago.
Anthropologists at Johannes Gutenberg University Mainz (JGU) and geneticists at University College London (UCL), working in collaboration with archaeologists from Berlin and Kiev, have analyzed ancient DNA from skeletons and found that selection has had a significant effect on the human genome even in the past 5,000 years, resulting in sustained changes to the appearance of people.
For a number of years population geneticists have been able to detect echoes of natural selection in the genomes of living humans, but those techniques are typically not very accurate about when that natural selection took place.
While investigating numerous genetic markers in archaeological and living individuals, Sandra Wilde of the Palaeogenetics Group at the JGU Institute of Anthropology noticed striking differences in genes associated with hair, skin, and eye pigmentation.
"Prehistoric Europeans in the region we studied would have been consistently darker than their descendants today," first author Wilde, said.
"This is particularly interesting as the darker phenotype seems to have been preferred by evolution over hundreds of thousands of years. All our early ancestors were more darkly pigmented," she said.
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However, things must have changed in the last 50,000 years as humans began to migrate to northern latitudes.
"In Europe we find a particularly wide range of genetic variation in terms of pigmentation," co-author Dr. Karola Kirsanow, who is also a member of the Palaeogenetics Group at Mainz University, said.
"However, we did not expect to find that natural selection had been favoring lighter pigmentation over the past few thousand years," Kirsanow said.
The signals of selection that the Mainz palaeogeneticists and their colleagues at University College London have identified are comparable to those for malaria resistance and lactase persistence, meaning that they are among the most pronounced that have been discovered to date in the human genome. The authors see several possible explanations.
"Perhaps the most obvious is that this is the result of adaptation to the reduced level of sunlight in northern latitudes," Professor Mark Thomas of UCL, corresponding author of the study, said.
"Most people of the world make most of their vitamin D in their skin as a result UV exposure. But at northern latitudes and with dark skin, this would have been less efficient. If people weren't getting much vitamin D in their diet, then having lighter skin may have been the best option," he added.
The results have been published in the journal Proceedings of the National Academy of Sciences (PNAS).