This is a great piece. It's unfortunate that someone like Gusev, who seems quite smart and capable, dismisses everything as coincidence and rejects the hereditarian position outright.
I'm glad you brought up the effect of education on IQ, particularly it's important distinction from the latent model of g. Schooling likely doesn't increase g itself in any sustained way; instead, education's impact on intelligence test scores stems from improvements in specific skills, not g. Even if education had a standardized effect on g, it would likely be minimal. From what I understand, there's no evidence of moderation (interactions) with the effect of schooling, as it would roughly be uniform across a child's genetic background or SES.
As you guys covered before, Gusev denies basically all classical behavioral genetics. Iirc he likes studies that use "controls" to adjust polygenic scores, but ignores that these controls can obfuscate plausible mechanisms.
Ironically as much as people criticize experts for misleading about hereditarianism, it was polls on intelligence researchers' opinion that really helped change my view (mainly in that I stopped constantly doubting my own read of the evidence). People who hold Gusev's opinion are just louder, because they can be. I think people would be less hostile about expertise if the media were honest and balanced about accurately portraying expert consensus using anonymous poll data.
Yes, I was going to ask if anyone had some comments on the family-based-weights for IQ GWAS which he posted here? They look bizarre to me, and I'm aware there's a great preponderance of other evidence in favour of the hereditarian position, but I'm curious as to what sleight of hand is being pulled here.
I think it's quite possible that cultural biases have worsened black IQ compared to their genetic potential in recent years, except I'm guessing the effect is in the opposite direction that Dr. Gusev assumes: that the broad effort by the American establishment during the Great Awokening, peaking during the Racial Reckoning of the early 2020s, to be more anti-white in order to be nicer to blacks instead wound up hurting blacks by demanding less of them, as seen by their NAEP scores, homicide rates, and traffic fatality rates in recent years.
the great (and very unfortunate) irony of woke racial justice. and the lower standards are not just hurting blacks, its hurting everyone. but no doubt, blacks disproportionately. ive seen this in real time as i have kids who are currently in public elementary, jr high and high school. standards have become almost non existent. (minneapolis, mn public schools).
"The size of this gap varies somewhat across time and region, but not by much. Indeed, one might venture a “law” of Black–White IQ differences: in nearly every subgroup examined, a gap of roughly one standard deviation between Blacks and Whites will appear."
I believe the blacks referred to are blacks living in white countries, many of which are not of pure black heritage; i.e, some white admixture. Using blacks of 100% black heritage, the difference is closer to one and a half standard deviations.
"Hereditarians think genes contribute, say, 20% or more of the gap, whereas environmental-only theorists think genes contribute less than 20%."
Based on the current information I have seen, I would say that 80% of the IQ gap is genetic and 20% is due to other factors.
Gusev and logic do not have a close working relationship.
The latest heritability number I have seen from twin studies was 0.83.
Note that Gusev discounts all twin studies. I discount Gusev.
You can look at the evidence to try and discern a pattern, or you can look at / filter the evidence to justify a prior belief. I think that the latter predominates with Gusev.
I wonder if artistic creativity in general (music, graphical arts, etc.) can be linked to IQ? If not, the implication is that artistic creativity is not based primarily in intellect, but rather, in some other human attribute.
This is not a criticism: I accept the hereditarian view as the best explanation for the statistical variation. I just like to explore the edge cases. Doing this provides much greater clarity.
There's a study of child prodigies that found some musical prodigies had very high all-round IQs, but one of the musical prodigies had an IQ of around 98, but a very high score for an aspect of intelligence that seemed to aid in musical learning and performance. So there is some correlation with IQ, but not as high as for say, physics or engineering. Also, look at the representation in the arts of some groups with low tested IQ.
I wonder if what is termed "intuition" can be characterized and measured, and if so, how it might relate to IQ.
WRT intuition, for a long, long time I did not believe in it, at all. But over my lifetime I believe that I have anecdotally observed increasing proficiency in my own ability to be enlightened intuitively.
It's nothing I'd care to bet on, but at this stage I do tend to listen to it in situations where no other concrete knowledge is available.
What I actually believe it to be in my case is a very large pool of life experience which subliminally informs me on many emergent situations. I think that it's basically background processing without a conscious trigger, just spontaneous input as the trigger. Runs constantly, maybe at night, not sure.
"I wonder if what is termed "intuition" can be characterized and measured, and if so, how it might relate to IQ."
Good question. I consider intuition to be a human trait. It would appear to be rather tricky to evaluate, but that would be a task for psychometricians.
"I wonder if artistic creativity in general (music, graphical arts, etc.) can be linked to IQ? If not, the implication is that artistic creativity is not based primarily in intellect, but rather, in some other human attribute."
Great point. I have often wondered the same. Perhaps musical ability is a special form of intelligence.
Knowing less about IQ than almost everyone else on this site, I would say that the chances of a low-IQ person painting a wonderful picture or composing a great work of music are only slightly higher than a chimpanzee at a typewriter typing out all the great books.
That said, I'm sure Picasso would say something like: the art of a [low IQ] child or the [low IQ] primitive in the Bush have an immediacy and power that taps into something profound and valuable that sophisicated modern man with his formalized education has lost.
Not sure if I buy that since I've never seen a drawing by a child or a primitive African that I wouldn't immediately throw into the next skip. Yet it's not impossible, and I've got to say that I prefer African-style dancing (i.e. going round and round in a circle for hours whilst stamping your feet) to almost any kind of more modern dancing, including ballroom, disco, the robot dance and, worst of all, artistic dance.
With all due respect, I've never been so triggered by a comment as by your last paragraph. Please tell me that you've never seen a proper ballet performance . . . It gives my life meaning!
My apologies Keith, I see you've qualified your statement already. Just goes to show how triggered I am. Seeing the Nutcracker later in life--admittedly a banal holiday tradition for many--absolutely re-booted my sense of truth, beauty and meaning in as profound a way as possible.
No problem, Tacet. I imagined you were speaking hyperbolically and half in jest and even if you weren't, your comment made me laugh.
I grew up in an environment where high art wasn't a thing. If I had wanted to acquire a love of ballet, classical music, art, red wine or blue cheese I would have had to strike out on my own and put in the work to acquire it.
Though I understand the argument that some things are not immediately appealing and need some work putting in, I have never been in favour of working at liking something. You start off trying to like ballet and 30 years later you find you have also acquired a taste for abominations like Jackson Pollack and progressive jazz and you ask yourself, 'What the hell happened to me?'
Consequently I still have the tastes of an adolescent: pop music, Coca-Cola, cake and spy novels. If I go to an art gallery it is only because I'm killing time before my bus leaves, not because art moves me.
When I hear music I often tap my feet or nod my head in time so clearly I'm not completely dead to these things. On the other hand I'm rarely tempted to stand up and do a pirouette. I suppose it all comes down to what you think music is for. For me it is not to tell a story but to make you want to nod along to it.
I believe people are genuine when they claim to be transported by music, art or ballet and part of me regrets missing out on a possible source of beauty. After all, there is little enough of that in the UK, which seems to grow uglier by the day.
Also I can see the appeal, without having to force myself, of watching a pretty lady cavort with grace and agility. Yet still there is something in me that baulks at such choreographed dance. The gap between initial impulse to move your body and polished performance is too great for me.
By the way, I can understand how seeing Nutcracker re-booted your sense of beauty, maybe even your sense of meaning, too, but I'd be really interested in hearing how it also re-booted your sense of truth. That sounds fascinating.
IQ tests are some of the most solid science in psychology.
By contrast, SES is an astonishingly crude measure of 'environment'.
For example, having 1 parent or 2 parents is not part of SES, but surely that is a huge factor in the environment of a child.
Can you imagine the outrage of Gusev if somebody tried to explain lower Black performance by noticing the reduced number of two parent Black families, compared to white families?
According to data from 2023, about 76.3% of white children lived in two-parent families, while only 44.6% of Black children lived in two-parent families
That seems like a smoking gun for the idea that environmental differences have a profound effect on Black children's educational attainment.
"According to data from 2023, about 76.3% of white children lived in two-parent families, while only 44.6% of Black children lived in two-parent families.
That seems like a smoking gun for the idea that environmental differences have a profound effect on Black children's educational attainment."
I disagree. A more definitive study would compare both white and black educational attainment from families with and without both parents.
Great piece. It seems to me that if there really is an environmental explanation for the Black-White IQ gap, it would be a "cultural" one. This was James Flynn's intuition, and although I disagree with it, it's a much better contender than education.
If education really raises intelligence, then why not intensify education? Also, are we supposed to believe that education has an infinite potential to raise Intelligence? Do environmentalists ever think about this? The implication would be that adults should continue going to school to keep raising their intelligence. Just imagine it, we could have millions of Einsteins. Obviously, this is a ridiculous idea.
It's sort of amazing how the cultural explanation is almost as tabooed as the genetic one (often considered a dog whistle for it).
That seems like it'd be the clear out yet liberals are choosing to run uphill by claiming the water level of American racism has been static for decades.
Another issue with Lewontin’s garden analogy is that the high within-group heritability is just due to environment variance within each garden being zero since the garden environment is uniform for both, but one garden is more uniformly deprived than the other. Within-group heritability estimates as it pertains to humans of course are derived from tremendous amounts of environmental variation that exists in the real world. So ultimately, it ends up just being a cute and technically true hypothetical that has basically zero relevance to differences between human populations.
I know this is an important topic but it must be frustrating to keep banging your head against this same brick wall. Someone who has gone into the subject fairly deeply, as Sasha Gusev must have done, yet still claims to think it unlikely that genetics plays a role in the black-white IQ gap, will never be brought to see it, regardless of the evidence that is wheeled on.
So Sasha Gusev is a smart guy and probably already knows the points that Bo raises. So what’s his deal? Does he have actual rebuttals or is this special pleading?
Non-B/W differences haven't been studied as intensively, but the data available broadly seems to be pointing to the same conclusions, including once PGS data comes into the picture.
With that said, I do recall Lynn noting that hispanic IQ was anomalously lower than you would expect given the test scores of native americans and the former's degree of white/euro ancestry. I was going to ask Bo/Aporia if they had any specific IQ vs. admixture studies looking at non-black hispanics?
Gusev sounds more and more like Eric Turkheimer to me. Turkheimer first put forth the three laws of behavioral genetics:
1) All human behavioral traits are heritable
2) The effect of being raised in the same family is smaller than the effect of genes
3) A substantial portion of the variation in complex human behavioral traits is not accounted for by the effects of genes or families,
Since then, Turkheimer has been backtracking on the three laws when more and more evidence came to support the three laws and the far left (which he is proudly a member of) didn't like that the evidence pointed to low African IQ.
Turkheimer is getting old and is probably tired of talking about this. Unlike Charles Murray (hehe). Gusev is the younger guy using his own credentials to debunk the ever growing evidence.
I don't think environmentalists have thought through the analogies they use.
'The first is the now-famous “corn seed” analogy forwarded by Richard Lewontin in which seeds are planted in two trays of vermiculite and watered with different nutrient solutions, one normal and one deficient in nitrates and lacking zinc. Unsurprisingly, the corn in the deficient tray is substantially shorter.'
If everybody gets bad conditions, everybody is stunted. Nobody will get the chance to shine.
But if everybody gets the same , good conditions, it is then that you will see how much better some groups are than others.
Improve education for all people, and the Black-white-Asian gaps will probably increase.
Education is 'one size fits all' and until the IQ differences are acknowledged and destigmatized (no one choosed to be born low IQ or short or red-headed) and different teaching methods developed, the needs of low IQ children will not be met. The professional teaching unions have limited the quality of teachers and teaching with their emphasis being more on pay and benefits than developing the teaching profession to address the differing abilities of students.
Darwin's Theory of Natural Selection means that population groups living in different environments will have descendants better adapted to those environments.
How different are the environments in which people around the world live in?
Let's take an analogy 'The second is an even more fantastical example from Freddie DeBoer in which children are either fitted with weighted belts or springy shoes and asked to participate in a jumping contest.'
Those are huge environmental differences.
Huge environmental differences will lead to huge genetic differences.
But proponents of 'Environmental differences are causing Black-White gaps' want to have both huge environmental differences and almost no genetic differences.
A bit like claiming that people who spend their lives carrying around weighted belts won't ever develop any extra muscle mass, or that elephants which have to carry a large mass won't be selected to have thicker legs
"Hereditarians think genes contribute, say, 20% or more of the gap, whereas environmental-only theorists think genes contribute less than 20%."
I realise this was just picturing the disagreement [from the point of view of hereditarians?] as a continuum with both sides merely arguing about the degree of genetic contribution rather than about mechanisms. But is that actually the case? Do environmental-only theorists accept that genes might contribute up to 20% of the gap and if so, shouldn't they change their name?
This is a great piece. It's unfortunate that someone like Gusev, who seems quite smart and capable, dismisses everything as coincidence and rejects the hereditarian position outright.
I'm glad you brought up the effect of education on IQ, particularly it's important distinction from the latent model of g. Schooling likely doesn't increase g itself in any sustained way; instead, education's impact on intelligence test scores stems from improvements in specific skills, not g. Even if education had a standardized effect on g, it would likely be minimal. From what I understand, there's no evidence of moderation (interactions) with the effect of schooling, as it would roughly be uniform across a child's genetic background or SES.
Meng Hu has an excellent write-up on this topic: https://humanvarieties.org/2022/12/22/schooling-enhances-iq-not-intelligence/
As you guys covered before, Gusev denies basically all classical behavioral genetics. Iirc he likes studies that use "controls" to adjust polygenic scores, but ignores that these controls can obfuscate plausible mechanisms.
Ironically as much as people criticize experts for misleading about hereditarianism, it was polls on intelligence researchers' opinion that really helped change my view (mainly in that I stopped constantly doubting my own read of the evidence). People who hold Gusev's opinion are just louder, because they can be. I think people would be less hostile about expertise if the media were honest and balanced about accurately portraying expert consensus using anonymous poll data.
Yes, I was going to ask if anyone had some comments on the family-based-weights for IQ GWAS which he posted here? They look bizarre to me, and I'm aware there's a great preponderance of other evidence in favour of the hereditarian position, but I'm curious as to what sleight of hand is being pulled here.
https://x.com/SashaGusevPosts/status/1905739085618274697
I think it's quite possible that cultural biases have worsened black IQ compared to their genetic potential in recent years, except I'm guessing the effect is in the opposite direction that Dr. Gusev assumes: that the broad effort by the American establishment during the Great Awokening, peaking during the Racial Reckoning of the early 2020s, to be more anti-white in order to be nicer to blacks instead wound up hurting blacks by demanding less of them, as seen by their NAEP scores, homicide rates, and traffic fatality rates in recent years.
the great (and very unfortunate) irony of woke racial justice. and the lower standards are not just hurting blacks, its hurting everyone. but no doubt, blacks disproportionately. ive seen this in real time as i have kids who are currently in public elementary, jr high and high school. standards have become almost non existent. (minneapolis, mn public schools).
Bo, thanks for another excellent article.
"The size of this gap varies somewhat across time and region, but not by much. Indeed, one might venture a “law” of Black–White IQ differences: in nearly every subgroup examined, a gap of roughly one standard deviation between Blacks and Whites will appear."
I believe the blacks referred to are blacks living in white countries, many of which are not of pure black heritage; i.e, some white admixture. Using blacks of 100% black heritage, the difference is closer to one and a half standard deviations.
"Hereditarians think genes contribute, say, 20% or more of the gap, whereas environmental-only theorists think genes contribute less than 20%."
Based on the current information I have seen, I would say that 80% of the IQ gap is genetic and 20% is due to other factors.
Gusev and logic do not have a close working relationship.
The latest heritability number I have seen from twin studies was 0.83.
Note that Gusev discounts all twin studies. I discount Gusev.
You can look at the evidence to try and discern a pattern, or you can look at / filter the evidence to justify a prior belief. I think that the latter predominates with Gusev.
I wonder if artistic creativity in general (music, graphical arts, etc.) can be linked to IQ? If not, the implication is that artistic creativity is not based primarily in intellect, but rather, in some other human attribute.
This is not a criticism: I accept the hereditarian view as the best explanation for the statistical variation. I just like to explore the edge cases. Doing this provides much greater clarity.
There's a study of child prodigies that found some musical prodigies had very high all-round IQs, but one of the musical prodigies had an IQ of around 98, but a very high score for an aspect of intelligence that seemed to aid in musical learning and performance. So there is some correlation with IQ, but not as high as for say, physics or engineering. Also, look at the representation in the arts of some groups with low tested IQ.
I wonder if what is termed "intuition" can be characterized and measured, and if so, how it might relate to IQ.
WRT intuition, for a long, long time I did not believe in it, at all. But over my lifetime I believe that I have anecdotally observed increasing proficiency in my own ability to be enlightened intuitively.
It's nothing I'd care to bet on, but at this stage I do tend to listen to it in situations where no other concrete knowledge is available.
What I actually believe it to be in my case is a very large pool of life experience which subliminally informs me on many emergent situations. I think that it's basically background processing without a conscious trigger, just spontaneous input as the trigger. Runs constantly, maybe at night, not sure.
"I wonder if what is termed "intuition" can be characterized and measured, and if so, how it might relate to IQ."
Good question. I consider intuition to be a human trait. It would appear to be rather tricky to evaluate, but that would be a task for psychometricians.
"I wonder if artistic creativity in general (music, graphical arts, etc.) can be linked to IQ? If not, the implication is that artistic creativity is not based primarily in intellect, but rather, in some other human attribute."
Great point. I have often wondered the same. Perhaps musical ability is a special form of intelligence.
Knowing less about IQ than almost everyone else on this site, I would say that the chances of a low-IQ person painting a wonderful picture or composing a great work of music are only slightly higher than a chimpanzee at a typewriter typing out all the great books.
That said, I'm sure Picasso would say something like: the art of a [low IQ] child or the [low IQ] primitive in the Bush have an immediacy and power that taps into something profound and valuable that sophisicated modern man with his formalized education has lost.
Not sure if I buy that since I've never seen a drawing by a child or a primitive African that I wouldn't immediately throw into the next skip. Yet it's not impossible, and I've got to say that I prefer African-style dancing (i.e. going round and round in a circle for hours whilst stamping your feet) to almost any kind of more modern dancing, including ballroom, disco, the robot dance and, worst of all, artistic dance.
With all due respect, I've never been so triggered by a comment as by your last paragraph. Please tell me that you've never seen a proper ballet performance . . . It gives my life meaning!
My apologies Keith, I see you've qualified your statement already. Just goes to show how triggered I am. Seeing the Nutcracker later in life--admittedly a banal holiday tradition for many--absolutely re-booted my sense of truth, beauty and meaning in as profound a way as possible.
No problem, Tacet. I imagined you were speaking hyperbolically and half in jest and even if you weren't, your comment made me laugh.
I grew up in an environment where high art wasn't a thing. If I had wanted to acquire a love of ballet, classical music, art, red wine or blue cheese I would have had to strike out on my own and put in the work to acquire it.
Though I understand the argument that some things are not immediately appealing and need some work putting in, I have never been in favour of working at liking something. You start off trying to like ballet and 30 years later you find you have also acquired a taste for abominations like Jackson Pollack and progressive jazz and you ask yourself, 'What the hell happened to me?'
Consequently I still have the tastes of an adolescent: pop music, Coca-Cola, cake and spy novels. If I go to an art gallery it is only because I'm killing time before my bus leaves, not because art moves me.
When I hear music I often tap my feet or nod my head in time so clearly I'm not completely dead to these things. On the other hand I'm rarely tempted to stand up and do a pirouette. I suppose it all comes down to what you think music is for. For me it is not to tell a story but to make you want to nod along to it.
I believe people are genuine when they claim to be transported by music, art or ballet and part of me regrets missing out on a possible source of beauty. After all, there is little enough of that in the UK, which seems to grow uglier by the day.
Also I can see the appeal, without having to force myself, of watching a pretty lady cavort with grace and agility. Yet still there is something in me that baulks at such choreographed dance. The gap between initial impulse to move your body and polished performance is too great for me.
By the way, I can understand how seeing Nutcracker re-booted your sense of beauty, maybe even your sense of meaning, too, but I'd be really interested in hearing how it also re-booted your sense of truth. That sounds fascinating.
IQ tests are some of the most solid science in psychology.
By contrast, SES is an astonishingly crude measure of 'environment'.
For example, having 1 parent or 2 parents is not part of SES, but surely that is a huge factor in the environment of a child.
Can you imagine the outrage of Gusev if somebody tried to explain lower Black performance by noticing the reduced number of two parent Black families, compared to white families?
According to data from 2023, about 76.3% of white children lived in two-parent families, while only 44.6% of Black children lived in two-parent families
That seems like a smoking gun for the idea that environmental differences have a profound effect on Black children's educational attainment.
"According to data from 2023, about 76.3% of white children lived in two-parent families, while only 44.6% of Black children lived in two-parent families.
That seems like a smoking gun for the idea that environmental differences have a profound effect on Black children's educational attainment."
I disagree. A more definitive study would compare both white and black educational attainment from families with and without both parents.
Great piece. It seems to me that if there really is an environmental explanation for the Black-White IQ gap, it would be a "cultural" one. This was James Flynn's intuition, and although I disagree with it, it's a much better contender than education.
If education really raises intelligence, then why not intensify education? Also, are we supposed to believe that education has an infinite potential to raise Intelligence? Do environmentalists ever think about this? The implication would be that adults should continue going to school to keep raising their intelligence. Just imagine it, we could have millions of Einsteins. Obviously, this is a ridiculous idea.
It's sort of amazing how the cultural explanation is almost as tabooed as the genetic one (often considered a dog whistle for it).
That seems like it'd be the clear out yet liberals are choosing to run uphill by claiming the water level of American racism has been static for decades.
Another issue with Lewontin’s garden analogy is that the high within-group heritability is just due to environment variance within each garden being zero since the garden environment is uniform for both, but one garden is more uniformly deprived than the other. Within-group heritability estimates as it pertains to humans of course are derived from tremendous amounts of environmental variation that exists in the real world. So ultimately, it ends up just being a cute and technically true hypothetical that has basically zero relevance to differences between human populations.
I know this is an important topic but it must be frustrating to keep banging your head against this same brick wall. Someone who has gone into the subject fairly deeply, as Sasha Gusev must have done, yet still claims to think it unlikely that genetics plays a role in the black-white IQ gap, will never be brought to see it, regardless of the evidence that is wheeled on.
So Sasha Gusev is a smart guy and probably already knows the points that Bo raises. So what’s his deal? Does he have actual rebuttals or is this special pleading?
Does this also apply to the Asian-White IQ gap?
Non-B/W differences haven't been studied as intensively, but the data available broadly seems to be pointing to the same conclusions, including once PGS data comes into the picture.
With that said, I do recall Lynn noting that hispanic IQ was anomalously lower than you would expect given the test scores of native americans and the former's degree of white/euro ancestry. I was going to ask Bo/Aporia if they had any specific IQ vs. admixture studies looking at non-black hispanics?
"Does this also apply to the Asian-White IQ gap?"
Of course. As well as the Ashkenazi-gentile gap.
Gusev sounds more and more like Eric Turkheimer to me. Turkheimer first put forth the three laws of behavioral genetics:
1) All human behavioral traits are heritable
2) The effect of being raised in the same family is smaller than the effect of genes
3) A substantial portion of the variation in complex human behavioral traits is not accounted for by the effects of genes or families,
Since then, Turkheimer has been backtracking on the three laws when more and more evidence came to support the three laws and the far left (which he is proudly a member of) didn't like that the evidence pointed to low African IQ.
Turkheimer is getting old and is probably tired of talking about this. Unlike Charles Murray (hehe). Gusev is the younger guy using his own credentials to debunk the ever growing evidence.
I don't think environmentalists have thought through the analogies they use.
'The first is the now-famous “corn seed” analogy forwarded by Richard Lewontin in which seeds are planted in two trays of vermiculite and watered with different nutrient solutions, one normal and one deficient in nitrates and lacking zinc. Unsurprisingly, the corn in the deficient tray is substantially shorter.'
If everybody gets bad conditions, everybody is stunted. Nobody will get the chance to shine.
But if everybody gets the same , good conditions, it is then that you will see how much better some groups are than others.
Improve education for all people, and the Black-white-Asian gaps will probably increase.
Education is 'one size fits all' and until the IQ differences are acknowledged and destigmatized (no one choosed to be born low IQ or short or red-headed) and different teaching methods developed, the needs of low IQ children will not be met. The professional teaching unions have limited the quality of teachers and teaching with their emphasis being more on pay and benefits than developing the teaching profession to address the differing abilities of students.
Gusev seems to follow the "Tribalism for me but not for thee" that is expected from someone of his background.
I'm not sure about it, but I think he's Slavic?
Darwin's Theory of Natural Selection means that population groups living in different environments will have descendants better adapted to those environments.
How different are the environments in which people around the world live in?
Let's take an analogy 'The second is an even more fantastical example from Freddie DeBoer in which children are either fitted with weighted belts or springy shoes and asked to participate in a jumping contest.'
Those are huge environmental differences.
Huge environmental differences will lead to huge genetic differences.
But proponents of 'Environmental differences are causing Black-White gaps' want to have both huge environmental differences and almost no genetic differences.
A bit like claiming that people who spend their lives carrying around weighted belts won't ever develop any extra muscle mass, or that elephants which have to carry a large mass won't be selected to have thicker legs
1) Huge environmental differences
2) Close genetic similarities.
Pick 1.
"Hereditarians think genes contribute, say, 20% or more of the gap, whereas environmental-only theorists think genes contribute less than 20%."
I realise this was just picturing the disagreement [from the point of view of hereditarians?] as a continuum with both sides merely arguing about the degree of genetic contribution rather than about mechanisms. But is that actually the case? Do environmental-only theorists accept that genes might contribute up to 20% of the gap and if so, shouldn't they change their name?