Justin’s Notes

The Caveat as Armor: What Coon's Empty Show of Hands Predicts About Ancient DNA

2026-07-26 · AI-generated insight

Place these two notes side by side and a live nerve appears. The ancient DNA paper reports that within the past ten millennia hundreds of alleles underwent strong directional selection, including shifts in "combinations of alleles that today predict complex traits"—decreased predicted body fat and schizophrenia, increased measures of cognitive performance. That last clause is exactly the sort of finding that the Coon episode teaches us the scientific community handles badly.

Recall what Coon documented: a professional association denouncing a book on racial differences when, by show of hands, only one member present had read it. Condemnation preceded examination. Trust in scientific authority, as the note argues, rests on the assumption that researchers weigh evidence before pronouncing. The Coon story is a clean counterexample.

Now watch how the geneticists behave. Notice the density of hedging around the cognitive result: these effects "were measured in industrialized societies, and it remains unclear how these relate to phenotypes that were adaptive in the past." That caveat is scientifically legitimate—but it is also load-bearing armor. The authors are pre-writing the defense against a room full of raised-or-unraised hands. They know the Coon dynamic is still operative, so they inoculate the paper against condemnation-without-examination by making the inflammatory sentence maximally difficult to quote in isolation.

Here is the pollination: the taboo Coon collided with did not disappear; it went underground and changed the grammar of scientific writing. Where 1961 anthropologists suppressed a claim by refusing to read it, 2024 geneticists smuggle the claim through by burying it in qualifications. Both are responses to the same threat—politics shaping what science may say aloud. One reaction is denial, the other is disciplined understatement.

The uncomfortable question the pairing raises: if the finding required this much defensive engineering to publish, how confident can readers be that the interpretation offered is the one the authors actually believe versus the one that survives peer review? The Coon note warns that trust erodes when scientists omit relevant facts. The ancient DNA note shows a subtler failure mode—not omission, but a fog of caveat that lets everyone read what they already wanted to.

Woven from these notes

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
Carleton Coon was one of the greatest anthropologists of the 20th century and a champion of the study of racial differences. In 1961 he was elected president of the American Anthropological Association. It was during this year that Carleton Putnam's infamous book Race and Reason came out. Putnam's book argued that there were significant differences between the races and that this had important political implications. A few anthropologists became upset when they saw the book gain popularity and wanted the AAA to intervene. But they knew that Coon supported the book and that, as a result, having the AAA take action against it would be difficult. So they organized a secret meeting behind Coon's back in order to issue a statement denouncing Putnam's work. Coon found out about the meeting and went to stop it. Upon entering the meeting Coon asked all the association members who had actually read Putnam's book to raise their hands. Only one rose. He then asked for the hands of everyone that had even heard of the book prior to that meeting. Only a few hands rose. None the less, the statement against the book passed. Coon, disgusted by the actions of his peers, resigned from the AAA (1). This incident stands out in the history of science as a particularly clear example of scientists not living up to what people expect of them. People often take what scientists say for granted. They trust that scientists have looked at the evidence rationally and are giving the public as accurate an account of all the relevant facts as they can. When explaining science to laypeople researchers are expected to only make authoritative statements on topics they are knowledgeable of, to not lie about scientific evidence, and to not omit obviously relevant facts. People trust scientists to do these things and so feel comfortable taking what they tell them for granted. (See