Justin’s Notes

The Evidence Arrives, but Hedged

2026-08-04 · AI-generated insight

Wade's complaint, in A Troublesome Inheritance, is essentially about a missing dataset. He argues that the Boasian doctrine—culture explains everything, humans are otherwise interchangeable—became entrenched not because the evidence demanded it but because the politics did. Recent human evolution, on his account, was simply asserted to be too slow or too trivial to matter, an assumption defended more by taboo than by measurement.

The ancient DNA study is, in a sense, the measurement he was waiting for. With nearly 16,000 West Eurasian genomes and a method built to separate genuine directional selection from the noise of migration, it reports hundreds of alleles under strong selection in the past ten millennia—including shifts, on the scale of modern variation, in predicted cognitive performance and schizophrenia risk. This is precisely the class of finding Wade insisted the field was suppressing: recent, ongoing, trait-relevant selection within the timeframe of settled human societies.

But read the two together and the more interesting thing is the register of the scientific paper. It does not triumphantly announce that biology drives social difference. It hedges hard: the trait effects 'were measured in industrialized societies, and it remains unclear how these relate to phenotypes that were adaptive in the past.' That sentence is doing enormous work. It concedes that a modern GWAS score for 'cognitive performance' need not have meant then what it seems to mean now.

So the pairing cuts in two directions at once. Against Boas, it confirms that recent selection on complex traits is real and pervasive—the blank slate is empirically dead. Against Wade, it demonstrates that the caution he read as political cowardice is often just methodological honesty: knowing that an allele frequency rose is not the same as knowing which phenotype it built, or why it paid off. The data he wanted have arrived, and they vindicate his premise while rebuking his confidence. Selection happened; what it selected for remains the genuinely open question, and the scientists refusing to fill that gap may be practicing rigor, not ideology.

Woven from these notes

The social scientists’ official view of race is designed to support the political view that genetics cannot possibly be the reason why human societies differ—the answer must lie exclusively in differing human cultures and the environment that produced them. The social anthropologist Franz Boas established the doctrine that human behavior is shaped only by culture and that no culture is superior to any other. From this point of view it follows that all humans are essentially interchangeable apart from their cultures, and that more complex societies owe their greater strength or prosperity solely to fortunate accidents such as that of geography.
— Nicholas Wade A Troublesome Inheritance: Genes, Race, and Human History
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