New research from the University of Zurich’s Centre for Evolutionary Medicine suggests that medieval Europeans had a similar level of lactose intolerance as modern day Europeans, meaning they could drink milk and eat yogurt and cheese without problems.
While milk is an important source of nutrition for infants, it also contains lactose sugar. Most adults in the world lose the ability to produce the enzyme lactase which is needed to digest the lactose, making them lactose intolerant: if they drink milk or eat a dairy product made from milk, they can suffer from bloating, nausea and even diarrhea. However, at least five populations in Europe, Saudi Arabia and East Africa have developed genetic mutations independently that allow them to produce lactase throughout their entire lives, a condition known as lactase persistence.
Dairy products have long been a central feature of European cuisine and cultural identity, and nowadays 60 – 90 percent of the European population is lactase persistent, which means they can digest milk in adulthood. Earlier studies on DNA samples taken from European farmers from around 5000 BC revealed a low lactase persistence rate. The earliest indications of lactase persistence to date were found among farmers in Spain during the Late Neolithic (approx. 3000 BC; 27 percent with lactase persistence) and Scandinavian hunter-gatherers (5 percent with lactase persistence). However, the question remains as to when and where humans began to exhibit a similar level of lactase persistence to us today.
This new study from the University of Zurich reveals a 72-percent lactase persistence rate among the population of the medieval town of Dalheim in Germany between 950 and 1200 AD, which indicates that lactase persistence had already reached modern Central European levels (71 – 80 percent) around 1000 years ago. Interestingly, these results contradict the previous research conducted on human remains from medieval Hungary, which exhibited a lactase persistence rate of 35 percent compared to 61 percent in the country today. The University of Zurich’s study therefore suggests that the evolution of lactase persistence did not follow a single pattern throughout Europe and that genetic lactase persistence may have been common in Central Europe earlier than in Eastern Europe.
“Undoubtedly, a number of factors played a role in the prevalence in different regions, such as different food and migration patterns,” explains Christina Warinner, the senior researcher on the University of Zurich’s study. “Our research reveals that lactase persistence already developed during the Middle Ages in Central Europe but this was clearly not the case everywhere on the continent.”
Nowadays, lactase persistence is so prevalent among Europeans and European-descendent populations in America and Australian that, until very recently, lactose intolerance was considered an abnormality, deficiency or disease. It was only when dairy products were promoted in national and international food campaigns in the mid-20th century that it became apparent that the majority of the global population is lactose-intolerant. Subsequent research has revealed that lactase persistence is actually the abnormal condition, resulting from the recent evolution of specific genetic mutations in certain populations.
The article, Ancient DNA analysis reveals high frequency of European lactase persistence allele (T-13910) in medieval Central Europe, appears in PLOS ONE. Click here to read this article.