In previous posts, I used EA4, a polygenic score for educational attainment, to predict standardized school test scores, and a height polygenic score to predict average height. Here I extend that approach to skin pigmentation, a trait that offers a more direct test of how genetic scores perform across populations.
Using polygenic scores to predict individual differences within populations is well established. Their use to compare population averages remains controversial. A score that predicts variation within one population does not automatically provide a reliable measure of differences between populations, because its estimated effects can depend on ancestry, environmental conditions and the design of the original study. [8]
For this test, I use a score extracted from a genome-wide association study of untanned skin colour. Pigmentation can be measured objectively on sun-protected skin, helping distinguish baseline colour from short-term changes due to sun exposure. My expectation is that, once those temporary fluctuations are set aside, baseline pigmentation is much less environmentally sensitive than height or educational outcomes. That makes it a useful benchmark for evaluating prediction across populations. [4,9]