Why Were the Yamnaya so Successful?An Evolutionary Polygenic Approach

Using ancient DNA from 414 Eurasian genomes and polygenic scores (PGS) derived from modern genome-wide association studies (GWAS), this study investigates whether the Yamnaya and related Steppe populations exhibited genetic predispositions that may have contributed to their historical success. PGS were calculated for various traits, including educational attainment (EA), height, cognitive function (IQ), skin pigmentation, and psychiatric conditions. To analyze temporal, geographic, and ancestry-specific effects, the study employed Pearson’s correlations, linear regression, and admixture modeling (ADMIXTURE). The results indicate that Steppe Pastoralist ancestry was associated with higher PGS for educational attainment (β = 0.268), height (β = 0.234), and autism spectrum disorder (ASD) (β = 0.201), and lower PGS for depression and schizophrenia (β = -0.198 and -0.192, respectively). In contrast, Anatolian Farmer ancestry showed a stronger association with higher EA PGS (β = 0.391) but lower height PGS (β = -0.523). Temporal analyses revealed upward trends in EA (r = -0.215) and height (r = -0.194) PGS over time, aligning with previous evidence for directional selection in Europe over the last 12,000 years. Modern Europeans, based on data from the 1000 Genomes Project, display genetically lighter skin (lower skin color PGS), higher PGS for EA and IQ, and lower PGS for anxiety, schizophrenia, and depression when compared to ancient populations.