David Reich: Cochran & Harpending Were Basically Right
There was indeed a "10,000 Year Explosion" of rapid human evolution since the Ice Ages ended.
Back in 2024 the SteveSailer substack covered the landmark preprint from the David Reich ancient DNA lab:
David Reich vindicates Cochran & Harpending’s “10,000 Year Explosion”
DNA scans of 8,433 ancient West Eurasians from the last 14,000 years finds there has been a lot of evolution since the Ice Age, including for IQ.
Note that Cochran and Harpending wrote right at the end of the ill-fated “candidate gene” era of genetics and just before the current polygenic score era focusing of many genes of small effect. Yet, they still tended to get the big picture right.
I followed up with:
Why no news coverage yet of David Reich’s epochal paper?
Reich is the Shohei Ohtani of ancient DNA, so why is his big 9/15/24 preprint still Not News Fit to Print?
As I pointed out a year and a half ago, one of the big names who signed on as a co-author of this paper was Eric S. Lander, who was President Biden’s Science Advisor. Lander is an establishment heavyweight, so the fact that he put his name to this stunning research suggested to me that these results couldn’t be sat on forever.
And, now, nineteen months later, Nature has published the paper:
Ancient DNA reveals pervasive directional selection across West Eurasia
Ali Akbari, Annabel Perry, Alison R. Barton, Mohammadreza Kariminejad, Steven Gazal, Zheng Li, Yating Zeng, Alissa Mittnik, Nick Patterson, Matthew Mah, Xiang Zhou, Alkes L. Price, Eric S. Lander, Ron Pinhasi, Nadin Rohland, Swapan Mallick & David Reich
I don’t have a Nature subscription (OK, not too bad at $199 per year), but the Reich lab provides free access to the updated PDF here.
The New York Times is taking the paper seriously now that it’s in Nature:
Nature Is Still Molding Human Genes, Study Finds
Some researchers hold that evolution hasn’t much altered humans in the past 10,000 years. A new analysis of ancient DNA indicates that natural selection continued to shape hundreds of genes.
By Carl Zimmer
April 15, 2026
Many scientists have contended that humans have evolved very little over the past 10,000 years.
A few hundred generations was just a blink of the evolutionary eye, it seemed. Besides, our cultural evolution — our technology, agriculture and the rest — must have overwhelmed our biological evolution by now.
A vast study, published on Wednesday in the journal Nature, suggests the opposite.
Here’s a pretty good tweet explaining the leaps forward:
@doctorveera
A new paper in @Nature from David Reich, @aliakbari23, and colleagues breaks the conventional understanding of recent human evolution. The field believed that strong selection in the recent past (~10,000 years) was rare, with few exceptions like the lactase persistence locus. In this paper, the authors challenge that belief, showing that we weren’t looking at the problem right.
Previous studies that looked for evidence of selection using ancient DNA addressed the problem cross-sectionally, asking if allele frequencies differed across populations more than what one would expect based on genetic drift and migration. Most arrived at the conclusion that population structure primarily explained the observed differences. Here, the authors addressed the problem longitudinally, accounting for when ancient individuals lived by explicitly modeling time as a variable in the analysis. It turns out doing it this way dramatically increases power, increasing the number of genome-wide significant selection signals by 20-fold!
Looking at why accounting for the time variable led to such dramatic changes in results, the authors find that previous studies missed so much because selection often happened not on new variants leading to dramatic sweeps (the conventional model: new variant -> selection -> increase in frequency) but on already existing variants driven by transient environmental pressures.
A classic example of an (apparently) new (semi-)favorable mutation was the sickle cell mutation, which appears to have happened in one African about 7,000 years. It’s favorable in the sense that if you inherit one copy of the mutation, you are more resistant to (very bad) falciparum malaria, at the cost of being a little bit lazier.
But if you inherit two copies, you die young.
So this is not a wholly optimized favorable mutation, probably because it’s relatively new. Hence, it’s only found in a minority of sub-Saharans.
In contrast, the Duffy-null mutation, which fights vivax malaria, emerged about 42,000 years ago and by now it’s pretty elegantly optimized to provide benefits without much in the way of costs. Thus, it’s found in almost all sub-Saharans.
There is a lot of genetic diversity out there. A lot of the variants don’t do much, good or bad, under some conditions. But change the conditions, such as the Ice Ages end and people invent farming, and some of these older variants can become highly useful. And, being older, they are less likely to have side-effects as destructive as the sickle cell mutation.
Many of these variants underwent reversals, selected up when a pressure existed, then purged when it disappeared or the trade-off cost became dominant. A great example is the TYK2 variant, where an allele boosting immunity was selected for thousands of years because it protected against TB, then got purged as TB endemicity declined and the autoimmune cost took over.
The scale of what they found is striking: hundreds of loci showing strong selection in the past 10,000 years with a median selection coefficient of ~0.86%. This number is pretty big in evolutionary terms, meaning allele frequencies have been shifting by ~1% per generation in a consistent direction. Previous selection scans found a maximum of 20 loci, and this one finds hundreds. That isn’t an incremental change. It fundamentally reframes our understanding of how common strong selection has been in recent human history.
Some of the most striking findings come from polygenic selection, where hundreds of small-effect alleles were pushed in the same direction simultaneously. Polygenic scores based on large-scale GWAS of today predict recent negative selection for traits like body fat, waist circumference and schizophrenia, and positive selection for others like cognitive traits. One important caveat is that GWAS phenotypes are measured in industrialized societies today, and how well they capture what was actually being selected in ancient environments is debatable.
For me personally, these findings have direct implications for drug discovery. When using human genetics to find drug targets, we often fixate on the benefit and risk profiles of variants visible today. But we need to be aware that a variant’s benefit:harm ratio might be environmentally contingent, and could reverse when the wrong environment manifests. An evolutionary understanding of a variant’s association with traits is therefore essential.
The same logic applies, perhaps even more urgently, to embryo selection. Selecting embryos based on polygenic traits is humans making permanent, heritable decisions for their offspring with a narrow view of today’s environment. The ancient DNA record now shows that cost-benefit landscapes flip over time. So, an embryo carrying man-made selections is carrying those changes into an unpredictable future environment.
The broader takeaway is that human evolution didn’t freeze in the last 10,000 years. We just lacked the tools and datasets to see its movement. The current findings are based on European populations. I am curious to see these analyses extended to other populations too, like South Asian, East Asian and African populations, which might be holding more surprises to blow our minds.
Yeah, but white scientists doing racial ancestry research on nonwhites is racist, so you may have a while to wait.
I often like the press releases that universities have PR staffers write to promote their professors’ papers. Here’s …
Paywall here.
