This paper proposes a population-genetic interpretation of reported Holocene polygenic score (PGS) trajectories for traits such as intelligence, educational attainment, schizophrenia, and walking pace. Rather than invoking sustained directional selection, the analysis shows that the magnitude and direction of these changes can be explained by purifying selection acting on the lower tail of the fitness distribution, combined with mutation–selection balance. A simple quantitative framework is introduced in which polygenic scores reflect changes in common variant components, while total genotypic value depends on the balance between selection and the accumulation of deleterious mutations. The results suggest that increasing PGS does not necessarily imply improvements in underlying genotypic performance.
Constantin Cretan (Sat,) studied this question.