1Department of Pre- and Protohistory, Institute of History, University of Zurich, Switzerland, 2Centre for Evolutionary Medicine, Institute of Anatomy, University of Zurich, Switzerland, 3Department of Anthropology, University of Oklahoma, USA
Thursday All day, Park Concourse
Milk and milk products are important foods in European, African, and Middle Eastern societies, but in other parts of the world lactose intolerance predominates. In mammals, lactase, the enzyme that hydrolyzes the milk sugar lactose, is normally down-regulated after weaning, but in Europe a single nucleotide polymorphism at -13910C/T in the gene MCM6 causes adult lactase persistence (LP). When and where this polymorphism evolved and the process by which it became the majority allele in Europe has been the subject of strong debate. A history of dairying is presumed to be a prerequisite, but current archaeological evidence is ambiguous.
In this study, DNA was extracted from the dentine of 36 individuals excavated at the Medieval (c. AD 1000-1200) cemetery of Dalheim in Germany. After PCR amplification and cloning, successful sequences were obtained for 25 individuals, of which 13 exhibited a European LP genotype (CT or TT).
Previous ancient DNA-based studies on the Neolithic found that the incidence of LP falls below detection levels in most regions. Our research shows that between the Neolithic and Medieval periods, the frequency of LP rose from near 0% to over 50%. Also, given that the frequency of LP genotypes in modern-day Germany is estimated at 78.5%, our results indicate that rather than being stable by the Medieval period, the lactase persistent genotype has continued to increase in frequency over the last 1000 years. This new evidence sheds light on the dynamic evolutionary history of the European lactase persistent trait and its global cultural implications.