Testing the Late Pleistocene Arctic Origins of East Asian Psychology using Ancient and Modern DNA

Abstract

Background

Climate variation during the Late Pleistocene and Holocene may have shaped human behavioral evolution through selection on personality-related genetic variants. However, direct evidence for climatically driven selection on behavioral polygenic scores (PGS) remains limited.

Methods

We tested for climate-linked selection on behavioral PGS using modern global genomes and ancient DNA from Western and Eastern Eurasia. PGS were computed for Extraversion, Agreeableness, and Neuroticism, and temporal trends were modeled with hinge regressions at 12,000 and 19,000 years before present (BP), adjusting for latitude and genomic coverage. In Eastern Eurasia, ancestry components were used to predict trait scores within the Holocene period.

Results

In modern populations, all three traits exhibited latitude-associated differentiation, consistent with cold-climate adaptation. In Western Eurasian ancient genomes, Extraversion and Neuroticism declined with sample age before the Last Glacial Maximum (pre-knot slopes ≈ −0.018 and −0.045 to −0.051 SD/kyr), then reversed direction after 12–19k BP (Δβ ≈ +0.036 to +0.104, all p < 0.001), suggesting post-LGM relaxation of selection. Agreeableness showed the complementary trend, increasing before and attenuating after the knots. A latent factor summarizing higher Agreeableness and lower Extraversion/Neuroticism captured these coordinated population-level shifts (Δβ ≈ −0.17, p < 0.001). In Eastern Eurasia, Holocene ancestry components (e.g., Jōmon, Tibetan, Northeast Chinese) predicted trait scores consistent with Arctic adaptation, while latitude effects weakened after accounting for admixture.

Conclusions

Both trait-specific and factor-level analyses indicate that Late Pleistocene cold climates intensified selection against Extraversion and Neuroticism while favoring Agreeableness, with Holocene warming leading to a reversal or relaxation of these pressures. These results support a model of climate-driven directional selection on behavioral tendencies across the Late Quaternary.