The Geographical Distribution of Lactose Tolerance-Associated Alleles 13910*T and 13915*G Is Strongly Linked to Male...

Lactose tolerance (lactase persistence) represents a very progressive human adaptation, the origins of which remain incompletely understood. This study aims to examine the geographical distribution of the two alleles associated with lactose tolerance in Eurasia (13910*T and 13915*G) in relation to the main Y haplogroups and autosomal ancestry components. Data on the frequency of the 13910*T allele were collected from 52 countries across Europe, the Near East, and North Africa. The 13915*G allele was available for 30 countries, but was studied in only 16 Near Eastern and North African countries, as it is absent in Europe. The findings indicate very robust, linear relationships between allele frequencies and the genetic factors examined. The strong correlation between the occurrence of the 13910*T allele and Yamnaya ancestry supports the hypothesis that 13910*T originated from the steppe Yamnaya culture. However, its subsequent dissemination can be attributed to a series of regional male founder events and the spread of specific Y haplogroups, particularly Y haplogroup I1. Conversely, the current occurrence of the 13915*G allele appears to have a less complex origin, associated with the geographically constrained expansion of pastoral populations with Natufian ancestry and Y haplogroup J1 in the Arabian Peninsula.