This is quite unexpected, as present-day Hungarians have noticeable lactase persistence (pdf; Yuval Itan et al., A worldwide correlation of lactase persistence phenotype and genotypes). The origin of lactase persistence in Europeans had been dated to no earlier than the onset of the Neolithic, as it was absent in early Neolithic Central Europeans, as well as northern European hunter-gatherers.
A scenario in which most of the selection for LP occurred over the last millennium is quite difficult to believe, and this would imply that there was an influx of LP-folk into the Hungarian population to account for its present-day frequency. We urgently need data on other contemporaneous European population to determine whether they had LP frequencies similar to the present-day ones or not.
My guess is that these 10th-11th century Hungarians comprised, in accordance to what physical anthropology suggests, a mix of Mongoloid and Caucasoid types of eastern origin, both of which are expected to be low on LP, while present-day Hungarians are largely descended from pre- and post-Hungarian Central European Caucasoids who possessed the regular (for central Europeans) high LP frequency.
Am J Phys Anthropol DOI: 10.1002/ajpa.21490
Comparison of lactase persistence polymorphism in ancient and present-day Hungarian populations
Dóra Nagy et al.
The prevalence of adult-type hypolactasia varies ethnically and geographically among populations. A C/T–13910 single nucleotide polymorphism (SNP) upstream of the lactase gene is known to be associated with lactase non-persistence in Europeans. The aim of this study was to determine the prevalence of lactase persistent and non-persistent genotypes in current Hungarian-speaking populations and in ancient bone samples of classical conquerors and commoners from the 10th–11th centuries from the Carpathian basin; 181 present-day Hungarian, 65 present-day Sekler, and 23 ancient samples were successfully genotyped for the C/T-13910 SNP by the dCAPS PCR-RFLP method. Additional mitochondrial DNA testing was also carried out. In ancient Hungarians, the T-13910 allele was present only in 11% of the population, and exclusively in commoners of European mitochondrial haplogroups who may have been of pre-Hungarian indigenous ancestry. This is despite animal domestication and dairy products having been introduced into the Carpathian basin early in the Neolithic Age. This anomaly may be explained by the Hungarian use of fermented milk products, their greater consumption of ruminant meat than milk, cultural differences, or by their having other lactase-regulating genetic polymorphisms than C/T-13910. The low prevalence of lactase persistence provides additional information on the Asian origin of Hungarians. Present-day Hungarians have been assimilated with the surrounding European populations, since they do not differ significantly from the neighboring populations in their possession of mtDNA and C/T-13910 variants.