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What David Reich thinks about evolutionary biology

@david-reich · 26 positions · 0 changes of mind

Geneticist at Harvard Medical School, whose laboratory studies human history and biological change through ancient DNA.

David Reich did not write this page.

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7 dated positions, 2026, in their own words. Our reading of what David Reich has said — not written or endorsed by them.

  1. Our readingPeriods of migration are the worst moments to look for natural selection, not the best, because they drown the signal in huge frequency swings.

    Their wordsAnd really from a statistical point of view, what happens at these times of migration is there's just huge fluctuations in frequencies, and these are extremely uninformative times for looking and detecting natural selection.

    ↗David Reich – Bronze Age shock, the Neanderthal puzzle, & the sudden spread of farmingyoutube.com 3rd of 26 in this recording

    Interesting

  3. Our readingNatural selection in humans has not been quiescent: it is tugging almost every position in the genome in one direction or another, everywhere.

    Their wordsIn fact, multiple analyses we do suggest that the genome is vibrating with natural selection, and uh there's all sorts of weaker effects that are there that would be picked up in larger studies even than we've done. Uh and that uh in fact, almost every position in the DNA is uh correlated to a position that in being dragged in one way or the other uh by natural selection. Instead of being quiescent, natural selection is everywhere.

    ↗David Reich – Bronze Age shock, the Neanderthal puzzle, & the sudden spread of farmingyoutube.com 4th of 26 in this recording

    Interesting

  5. Our readingFinding no selection in African-Americans over 300 years is not evidence against selection: five generations is simply too short a time to compound.

    Their wordsAnd so one possible explanation for that is just that there's only a handful of generations maybe five over which the natural selection would operate. And so maybe if the selection was 2% a generation you would still only see maybe a 10% compounded effect and there's just not enough time to detect it. But the Bronze Age is not 300 years, it's 3,000 years. It's the power of compound interest and you have enough time to begin to see a strong effect.

    ↗David Reich – Bronze Age shock, the Neanderthal puzzle, & the sudden spread of farmingyoutube.com 7th of 26 in this recording

    America

    Interesting

  7. Our readingSelection on the genetic predictors of cognitive performance peaked in the Bronze Age and has left no trace at all in the last 2,000 years.

    Their wordsAnd what you see when you look at intelligence is you see that this maxes out in the Bronze Age between 5,000, 4,000, 3,000, 2,000 years ago. And the impact in the last 2,000 years is almost nothing. There's no evidence of natural selection at all.

    ↗David Reich – Bronze Age shock, the Neanderthal puzzle, & the sudden spread of farmingyoutube.com 8th of 26 in this recording

    Interesting

  9. Our readingThe selection signal on the genetics of schooling is not a European artefact: the same variants predict years of school in China, a population disconnected from Europe for the whole period.

    Their wordsSo we just could not see a way this could happen by chance and once we saw that we really felt quite convinced that this was a real signal and that really somehow there has been natural selection to increase the genetic changes that today manifest themselves as more years of school at predicting more years of schooling.

    ↗David Reich – Bronze Age shock, the Neanderthal puzzle, & the sudden spread of farmingyoutube.com 10th of 26 in this recording

    EuropeChinaeducation

    Interesting

  11. Our readingThere is more room at the top for every human trait: push selection harder in any direction and the mean would move, at some cost elsewhere.

    Their wordsBut I think it's highly likely that if natural selection was pushed pushed any of these traits in more in one direction than it is, the mean would move.

    ↗David Reich – Bronze Age shock, the Neanderthal puzzle, & the sudden spread of farmingyoutube.com 15th of 26 in this recording

    Interesting

  13. Our readingA selection signal can be validated without a significance threshold, by measuring how far it is enriched for mutations an entirely independent study says affect a trait.

    Their wordsOur interpretation of this result is that once you slide the statistic above five, essentially all the signals of natural selection are real.

    ↗David Reich – Bronze Age shock, the Neanderthal puzzle, & the sudden spread of farmingyoutube.com 26th of 26 in this recording

    Interesting