Admixture as a source for HLA variation in Neolithic European farming communities.

Background: The northern European Neolithic is characterized by two major demographic events: immigration of early farmers from Anatolia at 7500 years before present, and their admixture with local western hunter-gatherers forming late farmers, from around 6200 years before present. The influence of this admixture event on variation in the immune-relevant human leukocyte antigen (HLA) region is understudied.

Results: We analyzed genome-wide data of 125 individuals from seven archeological early farmer and late farmer sites located in present-day Germany. The late farmer group studied here is associated with the Wartberg culture, from around 5500-4800 years before present. We note that late farmers resulted from sex-biased admixture from male western hunter-gatherers. In addition, we observe Y-chromosome haplogroup I as the dominant lineage in late farmers, with site-specific sub-lineages. We analyze true HLA genotypes from 135 Neolithic individuals, the majority of which were produced in this study. We observe significant shifts in HLA allele frequencies from early farmers to late farmers, likely due to admixture with western hunter-gatherers. Especially for the haplotype DQB1*04:01-DRB1*08:01, there is evidence for a western hunter-gatherer origin. The HLA diversity increased from early farmers to late farmers. However, it is considerably lower than in modern populations.

Conclusions: Both early farmers and late farmers exhibit a relatively narrow HLA allele spectrum compared to today. This coincides with sparse traces of pathogen DNA, potentially indicating a lower pathogen pressure at the time.