Justin’s Notes

The Op-Ed Was the Warning; the Paper Is the Payload

2026-07-20 · AI-generated insight

Read in sequence, these two notes trace a prophecy and its fulfillment. In the first, Reich stakes out a careful position: the orthodoxy insists population-level genetic differences in meaningful traits are trivial and that even asking is dangerous — and he warns, as a geneticist, that this stance is no longer tenable. It reads as a preemptive defense of work not yet published. The second note is that work, or its kin: ancient DNA across nearly 16,000 West Eurasians showing not the reassuring near-absence of hard sweeps, but hundreds of alleles under strong directional selection in just the last ten millennia — including shifts in predicted cognitive performance and schizophrenia risk.

This is precisely the forbidden terrain Reich named. His op-ed argued the slippery-slope anxiety cannot license ignorance; the paper then delivers findings whose every clause is politically radioactive. Notice how carefully the authors hedge: these effects were "measured in industrialized societies," and "it remains unclear how these relate to phenotypes that were adaptive in the past." That hedging is the op-ed's caution operationalized — a scientist walking the slope while roping himself to the cliff.

The sharpest irony is the shared filing under Culture Over Biology. Both notes are, in substance, evidence against that heading — biology moving fast, recently, and by natural selection rather than culture alone. The tag reads less as a claim the notes support than as the orthodoxy they are pushing against. The pairing suggests something the first note only gestures at: the reason such research feels dangerous is not that it might be wrong, but that the tools have gotten good enough for it to be right. The slippery slope isn't a slope of bad reasoning; it's a slope of resolution. As sample sizes grow and time-series methods sharpen, the "trivial differences" position stops being a scientific finding and becomes a decision not to look.

Woven from these notes

The orthodoxy maintains that the average genetic differences among people grouped according to today’s racial terms are so trivial when it comes to any meaningful biological traits that those differences can be ignored. The orthodoxy goes further, holding that we should be anxious about any research into genetic differences among populations. The concern is that such research, no matter how well-intentioned, is located on a slippery slope that leads to the kinds of pseudoscientific arguments about biological difference that were used in the past to try to justify the slave trade, the eugenics movement and the Nazis’ murder of six million Jews. I have deep sympathy for the concern that genetic discoveries could be misused to justify racism. But as a geneticist I also know that it is simply no longer possible to ignore average genetic differences among “races.”
— David Reich How Genetics Is Changing Our Understanding of 'Race'
Ancient DNA has transformed our understanding of population history, but its potential to reveal as much about human evolutionary biology has not been realized because of limited sample sizes and the difficulty of distinguishing sustained rises in allele frequency increasing fitness—directional selection—from shifts due to migrations, population structure, or non-adaptive purifying or stabilizing selection. Here we present a method for detecting directional selection in ancient DNA time-series data that tests for consistent trends in allele frequency change over time, and apply it to 15,836 West Eurasians (10,016 with new data). Previous work has shown that classic hard sweeps driving advantageous mutations to fixation have been rare over the broad span of human evolution8,9. By contrast, in the past ten millennia, we find that many hundreds of alleles have been affected by strong directional selection. We also document one-standard-deviation changes on the scale of modern variation in combinations of alleles that today predict complex traits. This includes decreases in predicted body fat and schizophrenia, and increases in measures of cognitive performance. These effects were measured in industrialized societies, and it remains unclear how these relate to phenotypes that were adaptive in the past. We estimate selection coefficients at 9.7 million variants, enabling study of how Darwinian forces couple to allelic effects and shape the genetic architecture of complex traits.
Ancient DNA reveals pervasive directional selection across West Eurasia