The study, titled Genome-wide Patterns of Selection in 230 Ancient Eurasians, was published by Nature and looked at ancient DNA of 230 West Eurasians who lived between 6500 and 300 BC, much of which came from completely new data. This data contains the first DNA from Anatolian Neolithic farmers, according to researchers.
Dr. Bastien Llamas, of The University of Adelaide and one of the authors of the study, told DairyReporter that researchers performed a hypothesis-free scan for genetic selection, pinpointing DNA changes that would be fixed through modern days that provide adaption of selective advantage.
“The results were thus mostly surprising, like unwrapping presents next to the Christmas tree,” he said.
4,500 years of digestion
The study found that Europeans were only able to start digesting dairy, such as cheese and milk, after Russian herders arrived from Great Steppes approximately 4,500 years ago, according to Llamas.
“Early European farmers could thus rely on the nutritional benefits of dairy products while avoiding the adverse effects of lactose intolerance,” he said.
While young children have the lactase enzyme, giving them the ability to digest lactose, the production of this enzyme may be 'switched off' and lactose becomes a natural toxin for adults. This is lactose intolerance, something that affects 65% of people worldwide.
However, Llamas said most modern-day Europeans have a mutation near the lactase gene that leads to lactase persistence, meaning most can drink milk without feeling ill.
“Our surprise finding is that the Russian pastoralists carried the lactase mutation found in modern-day Europeans,” he said. “Suddenly, the north-south gradient of lactase persistence frequency in Europe makes perfect sense.”
The distribution of lactase persistence in Europe is not random, Llamas said, as nearly all people living in Scandinavia and the British Isles are lactose tolerant. The frequency decreases south to Spain and Italy, he said, something this recent study helps explain.
Nature and culture’s balance
Llamas said this study showcases how nature and culture balance each other out over human history.
“It also shows that only a thorough study of the past using archaeological evidence and ancient DNA techniques can allow us to describe adaptation processes in real time,” he said.
“The natural adaptation to lactose tolerance rapidly spread in Northern Europe due to the selective advantage of relying on milk as a source of fat and protein,” according to Llamas. “Alternatively in Southern Europe, dairy processing was a powerful cultural adaptation that counteracted the spread of the lactase mutation.”
Source: Nature
doi:10.1038/nature16152
Genome-wide patterns of selection in 230 ancient Eurasians
Authors: I. Mathieson, I. Lazaridis, N. Rohland, S. Mallick, N. Patterson, S. Alpaslan Roodenberg, E. Harney, K. Stewardson, D. Fernandes, M. Novak, K. Sirak, C. Gamba, E. Jones, B. Llamas, S. Dryomov, J. Pickrell, J. Arsuaga, J. Bermúdez de Castro, E. Carbonell, F, Gerritsen, A. Khokhlov, P. Kuznetsov, M. Lozano, H. Meller, O. Mochalov