Lactose tolerance in adults originated in Southeastern Europe

New scientific study shows that milk production began in Southeastern Europe rather than in Northern Europe

28.08.2009

The ability to digest milk even as an adult developed among dairy farmers around 7,500 years ago in a region that stretched between the central Balkans and Central Europe. This is the conclusion announced in a new study conducted by researchers at the University College London (UCL) and Johannes Gutenberg University Mainz (JGU) that was recently published as the title story in the scholarly journal PLoS Computational Biology. Thus, the ability to digest lactose in milk after infancy - which is generally referred to as lactose tolerance - did not actually originate in Northern Europe as had originally been postulated.

"We now believe that lactose tolerance emerged about 7,500 years ago in a region that covers today's Hungary, Austria, and Slovakia. It perhaps emerged among the peoples of the Linear Pottery culture. It then spread among the entire Central and Northern European population with unbelievable alacrity," explains Professor Dr. Joachim Burger of the Institute of Anthropology at JGU. Today, an average of about 60% of the adult population in Central Europe is lactose tolerant, compared to only 20% in Southern Europe. There is almost complete lactose intolerance in most of the rest of the world.

Adult humans could not digest milk from the very beginning and the majority of the population of the globe still remains unable to digest milk. Most people lose the ability to break down the lactose in milk after infancy. This is due to a decrease in the production of the enzyme lactase which turns lactose into digestible sugars. Milk in its pure form can then no longer be digested, so it has to be made more tolerable for the body through special processes, such as those that turn milk into cheese or yogurt. As Professor Dr. Joachim Burger notes: "Other populations have come up with cultural solutions to lactose intolerance. But among our Neolithic ancestors in Central Europe, a genetic mutation developed which we call 'lactase persistence.' There is almost no other demographic characteristic that spread with the speed of this trait among the population." Research still needs to be done to determine exactly how this lactose tolerance was disseminated and how it was related to the emergence of animal husbandry - particularly in view of the fact that the first domestic cattle came to Europe from Anatolia about 8,000 years ago.

The scientific team, comprised of researchers from the elite British university UCL, the University of Reading, and the Institute of Anthropology at JGU, used a computer simulation for the current project. The program was employed to reproduce the potential spread of the genetic mutation among farmers involved in dairy production living in the midst of hunting and gathering populations. "We were somewhat surprised by the fact that Northern Europe is apparently not home to the origins of lactase persistence," explains Mark Thomas, senior author of the study and Professor of Evolutionary Genetics at UCL. "The present-day figures regarding the spread of this genetic mutation seemed to point toward the north, especially given that lactose tolerance among Northern Europeans in Scandinavia and Ireland is about 90%."

There are undoubtedly a number of different reasons related to genetic advantages that can help explain why lactose tolerance spread so quickly and in such a short time span in terms of evolutionary history. For example, in contrast to other agricultural products, milk is available all year round. Plus, the amount of energy that can be obtained by milking a cow is greater than that gained by slaughtering it. Purely demographic factors, such as the so-called surfing effect in an expanding population, may also account for the high frequency of tolerance in the north.

Outside of Europe, there are a also a number of small population groups in Africa known to possess the mutation for lactase persistence, although three of these groups probably developed this mutation entirely independently.

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