27 Comments
Mar 8Liked by Emil O. W. Kirkegaard

This kind of study is catnip for me! Just a few observations:

1. You should send a PDF to Mihai G. Netea, mihai.netea@radboudumc.nl and Yang Li, Yang.Li@helmholtz-hzi.de They found the same apparent increase in cognitive ability in post-Neolithic Europeans, while minimizing their finding:

"Although we see an increase in PRS for cognitive functions over time this does not necessarily translate to an evolutionary pressure towards an increasing intelligence. What this means is that there is an increase in allelic frequencies for alleles that positively impact multiple different measures of cognition but only to a limited extent in relation with the heritability of these traits."

https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2022.833190/full

2. If mean cognitive ability increased among Europeans from the Paleolithic to the Neolithic, how do you explain the decrease in cranial size during the same period? see:

Hawks, J. (2011). Selection for smaller brains in Holocene human evolution. arXiv:1102.5604 [q-bio.PE]

https://arxiv.org/abs/1102.5604

My explanation is that the cranial decrease was simply due to a decrease in mental storage of spatiotemporal data (due to the abandonment of hunting over large expanses of territory). We don't see this decrease in tropical humans who had hunted over smaller expanses. Do you have any other explanations?

3. "However, selection didn't seem to be stronger in England than in other places." If I understand correctly, the "other places" were other parts of northwestern Europe. Am I correct? Cognitive evolution in Clark's model was driven by the expansion of the middle class after c 1200 AD, and this was a phenomenon throughout northwestern Europe.

4. It's difficult to disentangle demographic replacement effects from selection effects. The estimate of 40 to 98% replacement of European hunter-gatherers by Anatolian farmers should thus be viewed with caution. The methodology assumes that demographic replacement explains all of the genetic change across the time boundary between hunter-gatherers and farmers. In reality, some of it was due to:

- founder effects, i.e., hunter-gatherers who adopted farming were a tiny percentage of all hunter-gatherers, hence the founder effects were considerable. This genetic change was random, but a certain percentage of it would have matched the genetic characteristics of Anatolian farmers.

- selection effects, i.e., hunter-gatherers who adopted farming were now adapting to the same regime of natural selection as that of Anatolian farmers. Hence there was some convergent evolution.

5. Cold winters theory doesn't really apply, since we're looking at the post-Paleolithic time window. Cognitive evolution during that period was driven much more by the demands of social complexification.

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I wrote about the Kuijpers study at length earlier. Their study is why we decided to do this more thorough analysis.

https://www.emilkirkegaard.com/p/ancient-eugenics-confirmed

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It might be interesting to get their feedback. At the very least, they should be informed about your study.

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2) If there was any evolution towards language/recursion/symbolic thought you can do more complex thinking with less neurons. Symbolic thought first demonstrated about 40kya (though some argue it goes back 2 million years). See for example the Shape of the Language Ready Brain: https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2014.00282/full

I collect some related research in this section as well: https://www.vectorsofmind.com/i/140565846/weak-etoc

4) Good point! Hadn't realized

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Really interesting plots. Best-fit trends are one thing -- but what do you make of the clear increases in variance that have occurred for all interpreted attributes over time? Is it just bigger sample size responsible for showing this increase in attribute range -- or is the central tendency of the genetics just increasingly decaying due to some kind of unspecified stress or stresses? Also, it occurs to me that this sort of interpretative enterprise is tautologically limited by the modern nature/preconceptions/assumptions of those doing the look-see, just like Big Tech's attempts at constructing AI are limited by the preferences and biases and assumptions of the AI programmers; i.e., hunter-gatherer 'intelligence' is not necessarily the same thing as the later observers' 'intelligence'. There is, no argument, that there was a structural discontinuity of some sort taking place during the Neolithic Revolution.

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Range is a function of sample size, not just variability. We didn't test for variance differences, as pooling from different locations at some times and not others would cause false positives for this.

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If there is something of a positive linear relationship between sample size and variability, I bet you there is still a large residual, though, that could be concealing all kinds of unconsidered things going on.

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I thought of it as herding people as opposed to farming people. The Scotts are a herding people compared to the English who are farming people. The Mongols vs. Chinese.

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Hm, for general purposes this might work, but I have to wonder if the IQ/autism and IQ/schiz correlation holds water or is much more complex than what's implied here. I would submit to you that I have traits for both, and my schiz/psychosis side is much smarter than my autism genetics though it is debatable as autism is more stable in general. I wonder if it's the correlation to epilepsy/psychosis and not schiz.

https://pubmed.ncbi.nlm.nih.gov/34967130/

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"Vikings did not seem to be particular bright:"

Well, according to some, they did manage to discover the North American landmass by boat before anyone else.

"An important finding, given my own writings, was that concerning cold winters theory:

However, the data do not support the cold winters theory of intelligence (Lynn, 1991, 2006), as the effect of latitude on EA3 and IQ in the regression models (Supplementary Tables S1 and S3) tended to be slightly negative (β = −0.055 and −0.097, p = .022 and p < .001 respectively), contrary to the theory’s prediction."

This theory always seemed lacking to me. The idea that cold climates drove cognitive ability for survival does not explain why humans' intelligence has progressed far beyond that necessary for survival.

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>which doesn't align with England's unique role in kicking off the industrial revolution.

I question this assumption. The co-invention of calculus by Newton and Leibniz at the same time combined with the failure of primitive races to industrialize strongly calls into question the popular-despite-low-evidence idea that the industrial revolution causally "spread" from Britain just because Britain was first by a decade or two.

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Could you elaborate on the point that England is somehow unique?

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Interesting paper. Is there any correction for the lower quality of ancient DNA? I know that is often an issue when looking at phenotype prediction in other areas, like hair and eye color. Also, I think it’s not unlikely that different genes in the past select for intelligence, causing a similar inaccuracy as you may see in non-western countries. This issue is furthered by the genetic changes Europe has gone through during the past 10,000 years. Modern Europeans have essentially no ancestry from the Paleolithic, and only a small fraction of direct ancestry from the Mesolithic WHGs.

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What kind of correction would you make? One can control for coverage (data quality) in the regression, but low quality does not affect means, it just lowers the accuracy.

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Maybe a good way to check this on another trait would be to compare PGS for height with the skeletal height of ancient samples?

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I don’t remember the details, and I’m not an expert on this stuff, but I’ve heard that low quality samples sometimes get skewed a certain way on HIrisPlex. Maybe that’s wrong. I would assume it would have to do with some alleles being more weighted than others, but all alleles decomposing at the same rate

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Hirisplex is for color traits, we are predicting massively polygenic traits here.

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Very interesting article, Why West Asian/Iranian ancestors considered separate from the Middle East? Aren't Iranians in general a genetic group close to Arabs?

I also noticed when reading the full article that Middle Eastern ancestry predicts lower intelligence, but not Iranian neolithic farmer ancestry.

Has there been a stronger pressure for intelligence in the Iranian plateau than in the Arabian Peninsula or the Fertile Crescent?

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Fascinating study, and from what I understand by far the most detailed one yet!

Interesting that BA Greece is mediocre. Many things could have changed in a millennium, but still, seems to be a point against Galton's hypothesis of Classical Greek IQs of 120?

> In the same way, many genomes come from cemeteries whose sampling may not be representative.

I think this is a critical issue? To estimate historical IQs from this, I would imagine one would need to classify social status of the buried individuals, read the historical literature on the estimated distribution of social classes, and adjust for that.

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Bronze Age Greece was not particularly noted for its intellectual or otherwise exceptional achievements. That would be Hellenistic Greece, in particular, Ionians—AFAIK there's no decently sized sample of Hellenistic Ionian DNA.

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Sure, as I mentioned, a lot of things could have changed in a millennium.

Though why that region would have accelerated - in fact, near-medieval Jewish level selection for higher IQ, if the claims of very high Classical Greek IQs are correct - would be a puzzle.

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Classical Greeks don't impress me all that much. Hellenistic Greeks are stunning tho. Archimedes' genius was probably unparalleled until ... Newton or maybe Gauss even. And his peers too, bizarrely singular people. Euclid's Elements was the standard textbook for two millennia. Eratosthenes, Aristarchus, Apollonius, Hipparchus, Philo, Eudoxus, Ctesibius: it's as if they arrive from the future, equipped with scientific method, and broach alien knowledge & technology to the Greco-Roman scene. And then poof, in two centuries, the moment is over: stillbirth of science.

And yeah, what drove fast selection for intelligence in Ionians, if it did happen, is likely to remain a mystery.

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Does this all assume that there isn’t any selection effect on genomes that are likely to be available over time? To me it seems that more recent genomes are much likelier to be an unbiased random sample of the population. Are there any reasons to suppose that genomes available from 500 or 1000 or more years ago are unbiased random samples of the population of the time?

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CW theory probably doesn’t play a huge role within Europe, since pretty much everywhere in Europe it gets cold enough that you need to plan for the winter quite a lot. ANE is not that relevant to CW theory since they were a Paleolithic Hunter gatherer population. CW is really dealing with more complex societies like Mesolithic and onwards

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Mar 7·edited Mar 7

Your paper, https://doi.org/10.1017/thg.2024.8, is behind a pay wall. Is there a version that is more accessiblein particular, info on how GWAS results predict IQ, EA, etc., especially wrt the error bars on random errors and the estimated effects of non-random errors.

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Mar 7Liked by Emil O. W. Kirkegaard

See researchgate -- it's there for public download.

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