Genetic Selection After the Black Death: Evidence for Behavioral but Not Cognitive Adaptation in Medieval Cambridge

The Black Death (1347–1351) devastated Medieval Europe with mortality rates of 30–60%, potentially creating selective pressure on cognitive and personality traits. We analyzed genomic data from 269 individuals from Medieval Cambridge to test whether the pandemic selected for intelligence-related traits (educational attainment polygenic scores, EA PGS) and personality traits (Extraversion PGS). Despite theoretical expectations, we found no significant difference in EA PGS between pre- and post-Black Death periods (Cohen’s d = -0.08, p = 0.394), challenging pandemic-driven cognitive selection hypotheses. However, Extraversion PGS significantly increased post-pandemic (Cohen’s d = 0.322, p = 0.01), suggesting behavioral rather than cognitive adaptation. Social stratification analysis revealed friars had the highest EA PGS while prosperous merchants had the lowest, indicating formal education, or the psychological traits associated with it, mattered more for religious roles than for commercial success. These findings suggest the Black Death’s genetic legacy was more behaviorally-oriented than previously assumed, with limited detectable selection on cognitive traits.