So I asked a similar question to a statistical geneticist (Gusev) whose priors are a bit different than Reich's (as he thinks recent selection is very uncommon and not on social/cognitive traits). He had a three-part principle-based response for explaining the likely trajectory of modern human cognitive repertoire: 1) Locus specific selection/hard sweeps are extremely rare (this is still largely consistent with the new Reich paper). 2) There isn't any current evidence that individual variants were involved in the great leap forward (The new Reich paper is consistent with this too as we're talking about directional selection on standing polygenic variation for the the complex traits). 3) Background selection (slow, persistent purging of novel alleles) explains the majority of human genetic variation.
The takeaway is that modern human cognitive abilities are likely much much older than when we can find evidence of them in the archaeological record. We can't generate great genetic insights because there isn't any DNA left from this period and we don't have great samples of ancient African DNA where a lot of important things happened. None of this forecloses mean or variance differences between different populations (Reich covers this in Ch.11 of his book). So the recent paper is observing interesting changes at the margin rather than the core of human capacities. Plus, whatever the human base cognitive capacities are, I think it's clear the special sauce is networking more and more individual human brains and preventing knowledge/technological decay over time. I think this also contributes to the Sapient Paradox as the learning curve to conscious sophistication with modern human hardware was itself gradual too. Recent changes are very interesting and meaningful (they do disrupt some dogma), but I don't think they remake how we understand the brain evolution that contributed to our core cognitive capacities.
There is more in the Reich book about why it's likely we emerged slowly. Even looking at how neurodevelopment and cognition are disrupted genetically today is revealing. The contribution of de novo variation is very important because the really important stuff is at fixation and constrained. Only really dramatic, typically new or less penetrant mutations/genetic changes (large deletions, trisomy 21, recessive LOF, etc) are culprits behind catastrophic intellectual/developmental deficits. We're still learning a lot on this front too like the recent snRNA gene findings (https://www.nature.com/articles/s41591-024-03085-5).
Thanks for the thoughtful reply. I suppose my biggest question is when you (or those that hold there hasn't been much recent cognitive evolution) think language evolved? What's your model? And additionally, why wouldn't we expect strong selection on intelligence or personality in the last 40,000 years? But going point by point
>So I asked a similar question to a statistical geneticist (Gusev) whose priors are a bit different than Reich's (as he thinks recent selection is very uncommon and not on social/cognitive traits).
What's the justification for such a prior? Say evolution or personality is 50% genetic. A highly networked society that produces art and religion must work better with certain personalities, right? If some personalities do 1% better, that is a lot of selection pressure over 10,000 or 50,000 years.
>1) Locus specific selection/hard sweeps are extremely rare
The recent paper "The role of genetic selection and climatic factors in the dispersal of anatomically modern humans out of Africa" found 57, half of which are neurological. Is that still extremely rare?
>2) There isn't any current evidence that individual variants were involved in the great leap forward
That paper interprets the neurological selection to be adaptation to cold Arabian nights. They mention that "provocatively" it could be related to symbolic thought, but the title of the paper advertises the climate angle. Part of my post is about how reticent geneticists are to grapple with the evolution of core human traits. Evidence of selection tends to be interpreted as window dressing.
There is a literature on self-domestication that often interprets genes as meaningful, and having experienced selection in the last 50,000 years. One of the linguists on the four-stage theory of language evolution has papers on the role of schizophrenia in the evolution of language, that reduction of schizophrenia was part of the domestication syndrome, and that alleles in scz PRS were likely selected for in this time period.
>whatever the human base cognitive capacities are, I think it's clear the special sauce is networking
When do you think language evolved?
I've read a fair bit in this space and those that argue for long timelines usually include the assumption that there has not been cognitive evolution in the last 20,000 years. It's a weird situation where the people who study what makes humans unique (usually linguists and anthropologists) point to the geneticists to say that there must not have been evolution in the last 100,000, 200,000 or 350,000 years. Often they couch it as anything in this time frame must be a rounding error on phenotypes.
A particularly dramatic case is The Recursive Mind by linguist Michael Corballis. Most of the book is a tight argument about how recursive thought explains human dominance: mental time travel, language, abstract thought, theory of mind, etc. Then when he dates this he says it must have been established by 200kya, citing genetic divergences and more sophisticated stone technology. He says he's "certain" that anyone from 200kya raised in today's society could become a doctor or scientist. But it's not clear why stone tech 200kya requires recursion; it is not a step change on any recursive ability. Very briefly, he also says that maybe recursive thought emerged in the Upper Paleolithic (when the first good evidence for it emerged). But in that case why is he certain that someone from 200kya is cognitively modern? It seems pretty obvious that he thinks recursion can explain human thought, but he's committed to the blank slate. And even then he entertains the possibility that recursion mostly evolved in the last 40,000 years.
Anyway, my point is that those who say there was a fallow period often justify that by saying evolution didn't happen recently. Demonstrating recent cognitive evolution should downgrade our belief in a fallow period.
>but I don't think they remake how we understand the brain evolution that contributed to our core cognitive capacities.
We don't really have an understanding though. Estimates for when language evolved are all over the place
>There is more in the Reich book about why it's likely we emerged slowly. Even looking at how neurodevelopment and cognition are disrupted genetically today is revealing. The contribution of de novo variation is very important because the really important stuff is at fixation and constrained.
Great points! I don't want to come across as "these people can't handle the truth." Human evolution really is mysterious, and if it does turn out language evolved recently it will mean surprising technical things. Reich hinted at this when Patel asked him what he'd put a million dollar bounty on discovering in genetics. He said "we really don't know how evolution works" and pointed to whether it tended to happen in a polygenetic fashion, or with just a few critical genes.
Honestly I wish we could have a betting market on when language or self-reflection evolved. What odds would you take on it evolving in the last 50,000 years? 100,000?
Lots of good questions! I'll try and be brief and stay point-by-point:
>My biggest question is when you (or those that hold there hasn't been much recent cognitive evolution) think language evolved? What's your model?
Reich has this nice figure in his book (Fig 5 Panel 3, page 51) illustrating the model I prefer. It shows the probability of shared ancestry across the whole genome in any large sample of humans over time and this peaks around 2mya. This is also around the same time that the modern FOXP2 emerges. Based on the natural FOXP2 het LOF mutants, we know FOXP2 is necessary for expressive speech (https://omim.org/entry/602081). I would suggest the core features of human language ability must have existed then. What level of language complexity existed among those humans? No idea. It was probably very simple language but all the biology was in place.
>And additionally, why wouldn't we expect strong selection on intelligence or personality in the last 40,000 years?
Over the last 40kya, I don't have a strong prior on whether there has or hasn't been strong selection. I imagine there has been some kind of selection, and the Reich papers suggest there was some in the last 10kya. However, this isn't the kind of selection that creating wholesale new abilities and traits. Plus, the selection effects may be swamped by other things going on. These look like tweaks that improve things at the margin. Check out Gusev's argument about why recent selection (<5000 kya) signals look minimal (https://theinfinitesimal.substack.com/p/where-are-the-recent-selective-sweeps).
>The recent paper "The role of genetic selection and climatic factors in the dispersal of anatomically modern humans out of Africa" found 57, half of which are neurological. Is that still extremely rare?
I have to read this paper in detail, and I'm sure there are debates about the methodologies and whether the signals are reliable and such because it can be hard to detect selection vs admixture/gene flow confidently. But if we just accept the claim here, 57 hard sweeps during 30kya stretch of OoA period, I'd say this is meaningful but not earth-shattering. There are 5000-8000 Mendelian gene - the ones likely subject to hard sweeps - so we're talking about at most 10% of these. Whether this is a lot or a small amount is perhaps a subjective judgement. Seems somewhat marginal biologically, but there are of course ways this could be meaningful to social narratives.
>We don't really have an understanding though. Estimates for when language evolved are all over the place
I agree that there is substantial uncertainty. I think this is mostly an argument is about where we should set our priors for future research on this question and for public communication of the state of the science. However, I'm sanguine that we'll make advances on these questions. I also want to emphasize that I think the invention of writing, which was not a biological adaptation, but a cultural advancement that repurposed existing ability was particular important to increasing social complexity and preventing the decay of knowledge.
>Great points! I don't want to come across as "these people can't handle the truth." Human evolution really is mysterious, and if it does turn out language evolved recently it will mean surprising technical things. Reich hinted at this when Patel asked him what he'd put a million dollar bounty on discovering in genetics. He said "we really don't know how evolution works" and pointed to whether it tended to happen in a polygenetic fashion, or with just a few critical genes.
I agree that the current models of evolution are flawed/sometimes misleading in some ways, and there is a lot of complexity to work out. Some things we just won't be able to answer because we don't have a perfect picture of the past. It is also obviously true that gene flow and admixture were important forces shaping model humans too. Reich speculates some in the interview and describes some evidence of in his book that hybridization events between different archaic humans were likely important in the emergence of modern humans.
>Honestly I wish we could have a betting market on when language or self-reflection evolved. What odds would you take on it evolving in the last 50,000 years? 100,000?
You could definitely make one on Manifold, but I don't know when or how we'd expect it to resolve. It would depend on how we define language ability or metacognition to me. If it is just the ability to speak some kind of simple declarative sentence that another could hear and understand, I'd take any odds this was something humans could do 100kya.
I think pair-bonding, shared parenting responsibilities, big game hunting, certain types of seasonal or time-sensitive foraging, butchery, and cooking all are clearly before 100kya and that they're dependent on verbal coordination.
>Over the last 40kya, I don't have a strong prior on whether there has or hasn't been strong selection. I imagine there has been some kind of selection, and the Reich papers suggest there was some in the last 10kya. However, this isn't the kind of selection that creating wholesale new abilities and traits.
It seems like the thing we should have *some* prior on. How much has fitness correlated with IQ in the last 50,000 years? With a heritability of 0.6, even with imperceptible correlations like r = 0.1, one expects to gain 72 IQ points every 2,000 years. Obviously, this doesn't make sense as you soon get negative numbers. But my point is that unless you have a strong prior r = 0, then you end up with a lot of selection on IQ. Enough that the population should have an average IQ of 50 or 0 back 10,000 or 50,000. years. IQ, obviously, doesn't make sense in those ranges. You get in the range where it's not clear there is *general* intelligence anymore. It just so happens, there is also a cultural phase change here that looks a lot like the emergence of general intelligence (or recursion, or language, etc).
So I think our substantial disagreement is on how much we can say about the fitness of intelligence. My stance is we can say a bit, and that's enough to understand that even with a very small fitness advantage there would be selection. Looking backwards you would expect a phase change away from human-level intelligence not to far back, and that's what we observe.
Also, even if your position is we can't say anything about the fitness of intelligence (ie, choose not to engage in a discussion of priors), then we should just follow the data, right? And Reich's data shows a 0.7 or 2.3 SD decrease in intelligence in the last 9,000 years, so do you go with those numbers? And we should assume similar selection pressure in the previous 40,000 years? Because that would produce the same conundrum, very quickly getting dropping below what is required for general intelligence.
>However, I'm sanguine that we'll make advances on these questions
Agreed. One of the reasons I write is that I think this stuff will be figured out in my lifetime.
>Reich speculates some in the interview and describes some evidence of in his book that hybridization events between different archaic humans were likely important in the emergence of modern humans.
It's interesting that in the preceeding tens of millennia before hybridization Homo Sapiens has just started scratching designs in rocks and Neanderthals had just started making musical instruments. Both had scattered signs of burial. Then right after mixing there is a flowering of art. It's a compelling story that some of the mixed offspring had the best of both worlds and started building a more complex culture.
>You could definitely make one on Manifold, but I don't know when or how we'd expect it to resolve.
You need god to make the market or something. Someone should look into this.
>It would depend on how we define language ability or metacognition to me. If it is just the ability to speak some kind of simple declarative sentence that another could hear and understand, I'd take any odds this was something humans could do 100kya.
Recursion! I'll bet declaratie sentences existed a long time ago. Maybe 2,000,000 years. Animals have a pretty broad range of calls, and Homo Erectus must have been a fairly smart animal.
>I think pair-bonding, shared parenting responsibilities, big game hunting, certain types of seasonal or time-sensitive foraging, butchery, and cooking all are clearly before 100kya and that they're dependent on verbal coordination.
On top of that, current GWAS don't support a 50% heritability for personality and intelligence, although I hope there are some things these methods are still missing. But I wouldn't bet my money on it. For example: CNVs, mtDNA (intelligence is more strongly correlated with the mother), Y chromosomes (bottlenecks), epigenetics (I don't think so), epistasis, etc.
There are certainly some things that are missed by the current molecular approaches. A lot of GWAS work ignores the sex chromosomes and rare variation. Rare variation has always been a holy Grail of sorts but there are some reasons to believe it doesn't contribute significantly to missing heritability for traits like intelligence but may do so for other high heritability psychiatric/neurodevelopmental traits.
It's also good to keep in mind that the genome continues to surprise us and heritability estimates are only one set of approaches to understand the nature of trait variance.
Andrew, what of the theory that the great northern Paleolithic ice-age hunters selected for higher intelligence, and that agriculture, technology and warm weather are factors which needn’t select for intelligence in order for more people to survive (ie a dummie can use a smart phone, without inventing it) therefore, lower IQ in modern populations compared to that of Paleolithic Eurasians has declined. Is there an article you can recommend? Thank you for inspiring me to read again 🤠🥰🧙
Well, my theory is that the most direct selection has been for identifiying with the inner voice from a young age---being self-aware at all. This is correlated with IQ, but obviously not exactly the same thing. To read more about that theory check out: https://www.vectorsofmind.com/p/eve-theory-of-consciousness-v3
“It’s not even obvious that non-Africans of today are even modern humans…” but Neanderthals who have experienced waves of admixture from Homo sapiens ! Omg 😱 mind blowing !!!! Love this. Would like to be Neanderthal .
Love this theorizing: once a large band of humans gained enough information and a culture to pass it on for subsequent generations to build on, human social cognition became a platform for gods: larger, incorporeal entities continually reified in the minds of human communities and populations because of their organizing power - with each existentially terrified human individual as host, deriving purpose and identity from the population’s organizing culture/spirits.
I don't know where this research stands today, but there are some climatic changes around this period in South Africa (in particular) that (if I recall correctly) ended round 70k when the environment became more hospitable. With evidence of innovation pulses and perhaps, in turn, of trade networks from then on, one might benefit from strong communication skills. Perhaps behavioral traits important to complex communication arise from recruiting standing variation and development of neural circuitry (?). Things continue from there and perhaps even aid in getting through tough times, population expansion, etc.
In comment thread with Stetson we discuss the recent paper "The role of genetic selection and climatic factors in the dispersal of anatomically modern humans out of Africa." It shows a 30 "hard sweeps" for genes related to the brain in the last 40,000 years, but then argues that was most likely due to climate adaptation 70,000-40,000 years ago. So the model you present is still preferred by some scientists, though I think the role of climate is exaggerated.
I agree that standing variation must be part of the story, as the splits in the family tree are so much deeper than 70,000 years
Climate is used by implicitly by proxy? Downstream effects like resource changes could be more likely to drive consumer population size, density, and variation (of all kinds).
Not by proxy, surprisingly. In the paper they say adapting to the cold puts selective pressure on the brain. That is their headline, even in the title. In the supplement they talk about how, "provocatively" it does align with more complex culture.
It's doubly surprising because so many fields have been pointing to genetics to say that no evolution has been happening recently. Anthropology, linguistics, comparative mythology, archeology, etc. And now the geneticists are saying, "about that..."
We have these modern groups branching away from each other a very long time ago, like West Africans diverting from non-African populations 100 K BP. This was *way* before archeological evidence of behaviorally modern humans, and yet West Africans are behaviorally modern. Did the parallel populations evolve the capacity for cumulative culture independently and simultaneously (which seems unlikely) or did all groups already have this cultural capacity 200K year ago?
Also how does the evidence for recent evolution of cognitive capability mesh with recent decline in brain size over the last 3K years?
>Did the parallel populations evolve the capacity for cumulative culture independently and simultaneously (which seems unlikely) or did all groups already have this cultural capacity 200K year ago?
That is the million dollar question, though those aren't the only two options. It could have been a gene-culture interaction. I also note that the splits are likely deeper than 200kya, going back more like 300kya. That is a lot of "fallow" time to justify. If the traits were established, why didn't we do anything with them?
>Also how does the evidence for recent evolution of cognitive capability mesh with recent decline in brain size over the last 3K years?
But if I had to comment I'd say that reduction in brain size is not inconsistent with evolution for more intelligence. Imagine that the brain is evolving to be able to run recursive algorithms which are far more efficient, or to be able to better use cultural knowledge rather than learn things from scratch. That would be more "intelligent" and potentially require less grey matter. FWIW, I believe that is the position of Heinrich and other supporters of the self-domestication hypothesis.
So I asked a similar question to a statistical geneticist (Gusev) whose priors are a bit different than Reich's (as he thinks recent selection is very uncommon and not on social/cognitive traits). He had a three-part principle-based response for explaining the likely trajectory of modern human cognitive repertoire: 1) Locus specific selection/hard sweeps are extremely rare (this is still largely consistent with the new Reich paper). 2) There isn't any current evidence that individual variants were involved in the great leap forward (The new Reich paper is consistent with this too as we're talking about directional selection on standing polygenic variation for the the complex traits). 3) Background selection (slow, persistent purging of novel alleles) explains the majority of human genetic variation.
The takeaway is that modern human cognitive abilities are likely much much older than when we can find evidence of them in the archaeological record. We can't generate great genetic insights because there isn't any DNA left from this period and we don't have great samples of ancient African DNA where a lot of important things happened. None of this forecloses mean or variance differences between different populations (Reich covers this in Ch.11 of his book). So the recent paper is observing interesting changes at the margin rather than the core of human capacities. Plus, whatever the human base cognitive capacities are, I think it's clear the special sauce is networking more and more individual human brains and preventing knowledge/technological decay over time. I think this also contributes to the Sapient Paradox as the learning curve to conscious sophistication with modern human hardware was itself gradual too. Recent changes are very interesting and meaningful (they do disrupt some dogma), but I don't think they remake how we understand the brain evolution that contributed to our core cognitive capacities.
There is more in the Reich book about why it's likely we emerged slowly. Even looking at how neurodevelopment and cognition are disrupted genetically today is revealing. The contribution of de novo variation is very important because the really important stuff is at fixation and constrained. Only really dramatic, typically new or less penetrant mutations/genetic changes (large deletions, trisomy 21, recessive LOF, etc) are culprits behind catastrophic intellectual/developmental deficits. We're still learning a lot on this front too like the recent snRNA gene findings (https://www.nature.com/articles/s41591-024-03085-5).
Thanks for the thoughtful reply. I suppose my biggest question is when you (or those that hold there hasn't been much recent cognitive evolution) think language evolved? What's your model? And additionally, why wouldn't we expect strong selection on intelligence or personality in the last 40,000 years? But going point by point
>So I asked a similar question to a statistical geneticist (Gusev) whose priors are a bit different than Reich's (as he thinks recent selection is very uncommon and not on social/cognitive traits).
What's the justification for such a prior? Say evolution or personality is 50% genetic. A highly networked society that produces art and religion must work better with certain personalities, right? If some personalities do 1% better, that is a lot of selection pressure over 10,000 or 50,000 years.
>1) Locus specific selection/hard sweeps are extremely rare
The recent paper "The role of genetic selection and climatic factors in the dispersal of anatomically modern humans out of Africa" found 57, half of which are neurological. Is that still extremely rare?
>2) There isn't any current evidence that individual variants were involved in the great leap forward
That paper interprets the neurological selection to be adaptation to cold Arabian nights. They mention that "provocatively" it could be related to symbolic thought, but the title of the paper advertises the climate angle. Part of my post is about how reticent geneticists are to grapple with the evolution of core human traits. Evidence of selection tends to be interpreted as window dressing.
There is a literature on self-domestication that often interprets genes as meaningful, and having experienced selection in the last 50,000 years. One of the linguists on the four-stage theory of language evolution has papers on the role of schizophrenia in the evolution of language, that reduction of schizophrenia was part of the domestication syndrome, and that alleles in scz PRS were likely selected for in this time period.
>whatever the human base cognitive capacities are, I think it's clear the special sauce is networking
When do you think language evolved?
I've read a fair bit in this space and those that argue for long timelines usually include the assumption that there has not been cognitive evolution in the last 20,000 years. It's a weird situation where the people who study what makes humans unique (usually linguists and anthropologists) point to the geneticists to say that there must not have been evolution in the last 100,000, 200,000 or 350,000 years. Often they couch it as anything in this time frame must be a rounding error on phenotypes.
A particularly dramatic case is The Recursive Mind by linguist Michael Corballis. Most of the book is a tight argument about how recursive thought explains human dominance: mental time travel, language, abstract thought, theory of mind, etc. Then when he dates this he says it must have been established by 200kya, citing genetic divergences and more sophisticated stone technology. He says he's "certain" that anyone from 200kya raised in today's society could become a doctor or scientist. But it's not clear why stone tech 200kya requires recursion; it is not a step change on any recursive ability. Very briefly, he also says that maybe recursive thought emerged in the Upper Paleolithic (when the first good evidence for it emerged). But in that case why is he certain that someone from 200kya is cognitively modern? It seems pretty obvious that he thinks recursion can explain human thought, but he's committed to the blank slate. And even then he entertains the possibility that recursion mostly evolved in the last 40,000 years.
Anyway, my point is that those who say there was a fallow period often justify that by saying evolution didn't happen recently. Demonstrating recent cognitive evolution should downgrade our belief in a fallow period.
>but I don't think they remake how we understand the brain evolution that contributed to our core cognitive capacities.
We don't really have an understanding though. Estimates for when language evolved are all over the place
>There is more in the Reich book about why it's likely we emerged slowly. Even looking at how neurodevelopment and cognition are disrupted genetically today is revealing. The contribution of de novo variation is very important because the really important stuff is at fixation and constrained.
Great points! I don't want to come across as "these people can't handle the truth." Human evolution really is mysterious, and if it does turn out language evolved recently it will mean surprising technical things. Reich hinted at this when Patel asked him what he'd put a million dollar bounty on discovering in genetics. He said "we really don't know how evolution works" and pointed to whether it tended to happen in a polygenetic fashion, or with just a few critical genes.
Honestly I wish we could have a betting market on when language or self-reflection evolved. What odds would you take on it evolving in the last 50,000 years? 100,000?
Lots of good questions! I'll try and be brief and stay point-by-point:
>My biggest question is when you (or those that hold there hasn't been much recent cognitive evolution) think language evolved? What's your model?
Reich has this nice figure in his book (Fig 5 Panel 3, page 51) illustrating the model I prefer. It shows the probability of shared ancestry across the whole genome in any large sample of humans over time and this peaks around 2mya. This is also around the same time that the modern FOXP2 emerges. Based on the natural FOXP2 het LOF mutants, we know FOXP2 is necessary for expressive speech (https://omim.org/entry/602081). I would suggest the core features of human language ability must have existed then. What level of language complexity existed among those humans? No idea. It was probably very simple language but all the biology was in place.
>And additionally, why wouldn't we expect strong selection on intelligence or personality in the last 40,000 years?
Over the last 40kya, I don't have a strong prior on whether there has or hasn't been strong selection. I imagine there has been some kind of selection, and the Reich papers suggest there was some in the last 10kya. However, this isn't the kind of selection that creating wholesale new abilities and traits. Plus, the selection effects may be swamped by other things going on. These look like tweaks that improve things at the margin. Check out Gusev's argument about why recent selection (<5000 kya) signals look minimal (https://theinfinitesimal.substack.com/p/where-are-the-recent-selective-sweeps).
>The recent paper "The role of genetic selection and climatic factors in the dispersal of anatomically modern humans out of Africa" found 57, half of which are neurological. Is that still extremely rare?
I have to read this paper in detail, and I'm sure there are debates about the methodologies and whether the signals are reliable and such because it can be hard to detect selection vs admixture/gene flow confidently. But if we just accept the claim here, 57 hard sweeps during 30kya stretch of OoA period, I'd say this is meaningful but not earth-shattering. There are 5000-8000 Mendelian gene - the ones likely subject to hard sweeps - so we're talking about at most 10% of these. Whether this is a lot or a small amount is perhaps a subjective judgement. Seems somewhat marginal biologically, but there are of course ways this could be meaningful to social narratives.
>We don't really have an understanding though. Estimates for when language evolved are all over the place
I agree that there is substantial uncertainty. I think this is mostly an argument is about where we should set our priors for future research on this question and for public communication of the state of the science. However, I'm sanguine that we'll make advances on these questions. I also want to emphasize that I think the invention of writing, which was not a biological adaptation, but a cultural advancement that repurposed existing ability was particular important to increasing social complexity and preventing the decay of knowledge.
>Great points! I don't want to come across as "these people can't handle the truth." Human evolution really is mysterious, and if it does turn out language evolved recently it will mean surprising technical things. Reich hinted at this when Patel asked him what he'd put a million dollar bounty on discovering in genetics. He said "we really don't know how evolution works" and pointed to whether it tended to happen in a polygenetic fashion, or with just a few critical genes.
I agree that the current models of evolution are flawed/sometimes misleading in some ways, and there is a lot of complexity to work out. Some things we just won't be able to answer because we don't have a perfect picture of the past. It is also obviously true that gene flow and admixture were important forces shaping model humans too. Reich speculates some in the interview and describes some evidence of in his book that hybridization events between different archaic humans were likely important in the emergence of modern humans.
>Honestly I wish we could have a betting market on when language or self-reflection evolved. What odds would you take on it evolving in the last 50,000 years? 100,000?
You could definitely make one on Manifold, but I don't know when or how we'd expect it to resolve. It would depend on how we define language ability or metacognition to me. If it is just the ability to speak some kind of simple declarative sentence that another could hear and understand, I'd take any odds this was something humans could do 100kya.
I think pair-bonding, shared parenting responsibilities, big game hunting, certain types of seasonal or time-sensitive foraging, butchery, and cooking all are clearly before 100kya and that they're dependent on verbal coordination.
>Over the last 40kya, I don't have a strong prior on whether there has or hasn't been strong selection. I imagine there has been some kind of selection, and the Reich papers suggest there was some in the last 10kya. However, this isn't the kind of selection that creating wholesale new abilities and traits.
It seems like the thing we should have *some* prior on. How much has fitness correlated with IQ in the last 50,000 years? With a heritability of 0.6, even with imperceptible correlations like r = 0.1, one expects to gain 72 IQ points every 2,000 years. Obviously, this doesn't make sense as you soon get negative numbers. But my point is that unless you have a strong prior r = 0, then you end up with a lot of selection on IQ. Enough that the population should have an average IQ of 50 or 0 back 10,000 or 50,000. years. IQ, obviously, doesn't make sense in those ranges. You get in the range where it's not clear there is *general* intelligence anymore. It just so happens, there is also a cultural phase change here that looks a lot like the emergence of general intelligence (or recursion, or language, etc).
(I actually did this back-of-the-envelope calculation last year to argue *against* IQ being supremely important: https://www.vectorsofmind.com/i/130101130/plato-aristotle-socrates-morons )
So I think our substantial disagreement is on how much we can say about the fitness of intelligence. My stance is we can say a bit, and that's enough to understand that even with a very small fitness advantage there would be selection. Looking backwards you would expect a phase change away from human-level intelligence not to far back, and that's what we observe.
Also, even if your position is we can't say anything about the fitness of intelligence (ie, choose not to engage in a discussion of priors), then we should just follow the data, right? And Reich's data shows a 0.7 or 2.3 SD decrease in intelligence in the last 9,000 years, so do you go with those numbers? And we should assume similar selection pressure in the previous 40,000 years? Because that would produce the same conundrum, very quickly getting dropping below what is required for general intelligence.
>However, I'm sanguine that we'll make advances on these questions
Agreed. One of the reasons I write is that I think this stuff will be figured out in my lifetime.
>Reich speculates some in the interview and describes some evidence of in his book that hybridization events between different archaic humans were likely important in the emergence of modern humans.
It's interesting that in the preceeding tens of millennia before hybridization Homo Sapiens has just started scratching designs in rocks and Neanderthals had just started making musical instruments. Both had scattered signs of burial. Then right after mixing there is a flowering of art. It's a compelling story that some of the mixed offspring had the best of both worlds and started building a more complex culture.
>You could definitely make one on Manifold, but I don't know when or how we'd expect it to resolve.
You need god to make the market or something. Someone should look into this.
>It would depend on how we define language ability or metacognition to me. If it is just the ability to speak some kind of simple declarative sentence that another could hear and understand, I'd take any odds this was something humans could do 100kya.
Recursion! I'll bet declaratie sentences existed a long time ago. Maybe 2,000,000 years. Animals have a pretty broad range of calls, and Homo Erectus must have been a fairly smart animal.
>I think pair-bonding, shared parenting responsibilities, big game hunting, certain types of seasonal or time-sensitive foraging, butchery, and cooking all are clearly before 100kya and that they're dependent on verbal coordination.
yes, agree with this list
I can't summarize the article here as I'm on the road, but I think you'll find many issues addressed in this article by Gusev: https://theinfinitesimal.substack.com/p/where-are-the-recent-selective-sweeps
I think it's kind of counterintuitive, but that doesn't mean it's not true, of course.
What do you think?
This seems to be the correct link https://theinfinitesimal.substack.com/p/where-are-the-recent-selective-sweeps
Thanks! I will edit it later!
On top of that, current GWAS don't support a 50% heritability for personality and intelligence, although I hope there are some things these methods are still missing. But I wouldn't bet my money on it. For example: CNVs, mtDNA (intelligence is more strongly correlated with the mother), Y chromosomes (bottlenecks), epigenetics (I don't think so), epistasis, etc.
There are certainly some things that are missed by the current molecular approaches. A lot of GWAS work ignores the sex chromosomes and rare variation. Rare variation has always been a holy Grail of sorts but there are some reasons to believe it doesn't contribute significantly to missing heritability for traits like intelligence but may do so for other high heritability psychiatric/neurodevelopmental traits.
It's also good to keep in mind that the genome continues to surprise us and heritability estimates are only one set of approaches to understand the nature of trait variance.
Andrew, what of the theory that the great northern Paleolithic ice-age hunters selected for higher intelligence, and that agriculture, technology and warm weather are factors which needn’t select for intelligence in order for more people to survive (ie a dummie can use a smart phone, without inventing it) therefore, lower IQ in modern populations compared to that of Paleolithic Eurasians has declined. Is there an article you can recommend? Thank you for inspiring me to read again 🤠🥰🧙
Well, my theory is that the most direct selection has been for identifiying with the inner voice from a young age---being self-aware at all. This is correlated with IQ, but obviously not exactly the same thing. To read more about that theory check out: https://www.vectorsofmind.com/p/eve-theory-of-consciousness-v3
“It’s not even obvious that non-Africans of today are even modern humans…” but Neanderthals who have experienced waves of admixture from Homo sapiens ! Omg 😱 mind blowing !!!! Love this. Would like to be Neanderthal .
Love this theorizing: once a large band of humans gained enough information and a culture to pass it on for subsequent generations to build on, human social cognition became a platform for gods: larger, incorporeal entities continually reified in the minds of human communities and populations because of their organizing power - with each existentially terrified human individual as host, deriving purpose and identity from the population’s organizing culture/spirits.
I don't know where this research stands today, but there are some climatic changes around this period in South Africa (in particular) that (if I recall correctly) ended round 70k when the environment became more hospitable. With evidence of innovation pulses and perhaps, in turn, of trade networks from then on, one might benefit from strong communication skills. Perhaps behavioral traits important to complex communication arise from recruiting standing variation and development of neural circuitry (?). Things continue from there and perhaps even aid in getting through tough times, population expansion, etc.
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In comment thread with Stetson we discuss the recent paper "The role of genetic selection and climatic factors in the dispersal of anatomically modern humans out of Africa." It shows a 30 "hard sweeps" for genes related to the brain in the last 40,000 years, but then argues that was most likely due to climate adaptation 70,000-40,000 years ago. So the model you present is still preferred by some scientists, though I think the role of climate is exaggerated.
I agree that standing variation must be part of the story, as the splits in the family tree are so much deeper than 70,000 years
Climate is used by implicitly by proxy? Downstream effects like resource changes could be more likely to drive consumer population size, density, and variation (of all kinds).
Not by proxy, surprisingly. In the paper they say adapting to the cold puts selective pressure on the brain. That is their headline, even in the title. In the supplement they talk about how, "provocatively" it does align with more complex culture.
As someone currently teaching ANTHR 101 the moment where Reich calls our current model “low probability” was both 😬 and 🤔
I am excited but wonder if the knowledge I am about to give a test on will even survive the term?
Is that the sound of a khunian revolution?
It's doubly surprising because so many fields have been pointing to genetics to say that no evolution has been happening recently. Anthropology, linguistics, comparative mythology, archeology, etc. And now the geneticists are saying, "about that..."
Totally!
We have these modern groups branching away from each other a very long time ago, like West Africans diverting from non-African populations 100 K BP. This was *way* before archeological evidence of behaviorally modern humans, and yet West Africans are behaviorally modern. Did the parallel populations evolve the capacity for cumulative culture independently and simultaneously (which seems unlikely) or did all groups already have this cultural capacity 200K year ago?
Also how does the evidence for recent evolution of cognitive capability mesh with recent decline in brain size over the last 3K years?
>Did the parallel populations evolve the capacity for cumulative culture independently and simultaneously (which seems unlikely) or did all groups already have this cultural capacity 200K year ago?
That is the million dollar question, though those aren't the only two options. It could have been a gene-culture interaction. I also note that the splits are likely deeper than 200kya, going back more like 300kya. That is a lot of "fallow" time to justify. If the traits were established, why didn't we do anything with them?
>Also how does the evidence for recent evolution of cognitive capability mesh with recent decline in brain size over the last 3K years?
I don't think it's accurate to say "in the last 3k years" like it's a global phenomenon. That figure comes from fitting a model to very messy data, check it out: https://x.com/AndrewCutler13/status/1701635738918338787
But if I had to comment I'd say that reduction in brain size is not inconsistent with evolution for more intelligence. Imagine that the brain is evolving to be able to run recursive algorithms which are far more efficient, or to be able to better use cultural knowledge rather than learn things from scratch. That would be more "intelligent" and potentially require less grey matter. FWIW, I believe that is the position of Heinrich and other supporters of the self-domestication hypothesis.