Justin’s Notes

Single Loci vs. Correlation Structure: Where Lewontin's Argument Breaks

2026-09-18 · AI-generated insight

These two notes stage a genuine collision, and the fault line runs through a statistical subtlety rather than a moral one. Lewontin's famous finding — that most human genetic variation lies within populations rather than between them — is empirically true and has anchored the "race has no biological reality" position for fifty years. But notice how the note is filed: Correlation Across Many Variables. That filing names the exact weakness Edwards later called "Lewontin's fallacy." Any single randomly chosen locus tells you little about population membership; the aggregate correlation structure across thousands of loci classifies individuals into continental ancestry groups with near-perfect accuracy. Lewontin's argument is an argument about marginal distributions deployed against a question about joint distributions.

Warne's five lines of evidence live entirely in that joint-distribution world. Polygenic scores are nothing but weighted sums across many loci — they exist precisely because information that is negligible at each variant becomes substantial in aggregate. Admixture studies likewise depend on ancestry being genomically legible in a way Lewontin's framing implies it shouldn't be. So the debate isn't really "genetics says X" versus "genetics says Y"; it's a debate about whether you're allowed to sum.

There's a second asymmetry worth noting. Lewontin leaps from an empirical claim to a normative one in a single breath: racial classification is "positively destructive" and therefore no justification exists for it. Warne moves in the opposite direction, fencing his claim with caveats — >0% but of unknown magnitude, US-born native English speakers only, data "not fully conclusive." One can read this charitably (Warne is epistemically careful where Lewontin is motivated) or suspiciously (hedged framing is how contested claims get smuggled into respectability). Either way, the notes together illustrate a recurring pattern in politically charged science: the side claiming the moral high ground tends to argue from single variables and sweeping conclusions, while the side claiming the empirical high ground argues from aggregates and hedges. The honest synthesis is uncomfortable — Lewontin's statistic is true but doesn't support his conclusion, and Warne's methods are sound but can't yet deliver the effect size that would make his claim consequential.

Woven from these notes

The past 30 years of research in intelligence has produced a wealth of knowledge about the causes and consequences of differences in intelligence between individuals, and today mainstream opinion is that individual differences in intelligence are caused by both genetic and environmental influences. Much more contentious is the discussion over the cause of mean intelligence differences between racial or ethnic groups. In contrast to the general consensus that interindividual differences are both genetic and environmental in origin, some claim that mean intelligence differences between racial groups are completely environmental in origin, whereas others postulate a mix of genetic and environmental causes. In this article I discuss 5 lines of research that provide evidence that mean differences in intelligence between racial and ethnic groups are partially genetic. These lines of evidence are findings in support of Spearman’s hypothesis, consistent results from tests of measurement invariance across American racial groups, the mathematical relationship that exists for between-group and within-group sources of heritability, genomic data derived from genome-wide association studies of intelligence and polygenic scores applied to diverse samples, and admixture studies. I also discuss future potential lines of evidence regarding the causes of average group differences across racial groups. However, the data are not fully conclusive, and the exact degree to which genes influence intergroup mean differences in intelligence is not known. This discussion applies only to native English speakers born in the United States and not necessarily to any other human populations.
— Russell Warne Between-Group Mean Differences in Intelligence in the United States Are >0% Genetically Caused: Five Converging Lines of Evidence
It is clear that our perception of relatively large differences between human races and subgroups, as compared to the variation within these groups, is indeed a biased perception and that, based on randomly chosen genetic differences, human races and populations are remarkably similar to each other, with the largest part by far of human variation being accounted for by the differences between individuals. Human racial classification is of no social value and is positively destructive of social and human relations. Since such racial classification is now seen to be of virtually no genetic or taxonomic significance either, no justification can be offered for its continuance.
— Lewontin