53 minutes ago, TheVat said:

https://onlinelibrary.wiley.com/doi/abs/10.1002/ajpa.24216

American Journal of Physical AnthropologyVolume 175, Issue 2 pp. 465-476

Abstract

Objectives

Debate about the cause of IQ score gaps between Black and White populations has persisted within genetics, anthropology, and psychology. Recently, authors claimed polygenic scores provide evidence that a significant portion of differences in cognitive performance between Black and White populations are caused by genetic differences due to natural selection, the “hereditarian hypothesis.” This study aims to show conceptual and methodological flaws of past studies supporting the hereditarian hypothesis.

Materials and methods

Polygenic scores for educational attainment were constructed for African and European samples of the 1000 Genomes Project. Evidence for selection was evaluated using an excess variance test. Education associated variants were further evaluated for signals of selection by testing for excess genetic differentiation (F_st). Expected mean difference in IQ for populations was calculated under a neutral evolutionary scenario and contrasted to hereditarian claims.

Results

Tests for selection using polygenic scores failed to find evidence of natural selection when the less biased within-family GWAS effect sizes were used. Tests for selection using F_st values did not find evidence of natural selection. Expected mean difference in IQ was substantially smaller than postulated by hereditarians, even under unrealistic assumptions that overestimate genetic contribution.

Conclusion

Given these results, hereditarian claims are not supported in the least. Cognitive performance does not appear to have been under diversifying selection in Europeans and Africans. In the absence of diversifying selection, the best case estimate for genetic contributions to group differences in cognitive performance is substantially smaller than hereditarians claim and is consistent with genetic differences contributing little to the Black–White gap.

A couple points:

One, please provide citations rather than "what I recall reading," as our forum rules require you to do when requested. We need to see the data you're seeing and how it's being interpreted.

Two, twin studies are prone to sloppiness in isolating causal factors. Adopted children generally, for example, receive somewhat differential treatment from biological children in a given family no matter how good the parental intentions or the degree of wealth. There can also be overseas effects for children adopted into richer Western families, where a shift in various environment features in the first year or two of life (ambient allergens or pathogens, for one) can affect the child's development.

That study is interesting - if I've understood it correctly they linked educational attainment to particular genes in a sample of genomes of Black and White populations, estimated the degree to which those genes had been influenced by selection effects, and then calculated the expected differential in mean IQ between the populations based on some kind of simulation that made use of this information. They found the expected difference to be less than that of what hereditarians have claimed, and concluded that that position is not well supported.

That's pretty cool and if the methodology is sound it's a useful advance, but I don't think it conclusively disproves the hereditarian (or at least "soft hereditarian") position. Educational attainment is just one imperfect metric, and there is a lot of room for error to leak in with the methods they used.

I'll have to dig up one of the twin studies I'm talking about later.

The reasons I cling to hereditarian ideas are the following:

1. Your mind is your brain. Your brain is a part of your body. I don't see how you can deny that it is subject to genetic influence.

2. Assuming IQ is a valid measure of some property of the mind (brain), the historically measured gaps in IQ (and their measurement is basically factual) have persisted for so long and across so much societal change it seems difficult to imagine how they could be purely environmental in origin. Even just looking at score results from say the early 20th century to the 1980s (before the more recent data) the gap remained fairly constant even with the Flynn effect. If this was the result of improvements to environmental conditions, it seems unlikely that both populations would experience nearly identical rates of improvement if the sole cause of the disparity to begin with was environmental factors.

3. I wonder more generally just how much of an effect environmental interventions can have on fluid intelligence beyond the basics, like adequate nutrition, shelter, and basic socialization and education. I recall reading (and I can retrieve these studies later with the others) that several focused intervention style programs intended to increase g in select groups had basically no effect. Most people in developed countries have access to these necessities, so it seems like further significant differentiation would be due to innate traits.

Edited November 29Nov 29 by xenog123
Added point 3

2 hours ago, xenog123 said:

The reasons I cling to hereditarian ideas are the following:

1. Your mind is your brain. Your brain is a part of your body. I don't see how you can deny that it is subject to genetic influence.

2. Assuming IQ is a valid measure of some property of the mind (brain), the historically measured gaps in IQ (and their measurement is basically factual) have persisted for so long and across so much societal change it seems difficult to imagine how they could be purely environmental in origin. Even just looking at score results from say the early 20th century to the 1980s (before the more recent data) the gap remained fairly constant even with the Flynn effect. If this was the result of improvements to environmental conditions, it seems unlikely that both populations would experience nearly identical rates of improvement if the sole cause of the disparity to begin with was environmental factors.

3. I wonder more generally just how much of an effect environmental interventions can have on fluid intelligence beyond the basics, like adequate nutrition, shelter, and basic socialization and education. I recall reading (and I can retrieve these studies later with the others) that several focused intervention style programs intended to increase g in select groups had basically no effect. Most people in developed countries have access to these necessities, so it seems like further significant differentiation would be due to innate traits.

4. You''re a bleached, inbred, hillbilly halfwit.

Go on, tell me why exactly you find that such an objectionable comment. I dare you.

Your username gives away exactly where you're coming from. A seriously low IQ error of judgment.

32 minutes ago, sethoflagos said:

4. You''re a bleached, inbred, hillbilly halfwit.

Go on, tell me why exactly you find that such an objectionable comment. I dare you.

Your username gives away exactly where you're coming from. A seriously low IQ error of judgment.

I wasn't sure what xenog was short for, unless it was xenogenesis, as in the Octavia Butler novels. Which would be, at this point, ironic given Butler's ethnic origins.

Anyway, one can actually use your hillbilly reference to observe that no one has come up with a conjecture that rural folk of Scots-Irish descent in Appalachia have consistently shown lower IQ scores for many generations due to their ethnic origins. Funny how that works, eh?

2 hours ago, xenog123 said:

I wonder more generally just how much of an effect environmental interventions can have on fluid intelligence beyond the basics, like adequate nutrition, shelter, and basic socialization and education. I recall reading (and I can retrieve these studies later with the others) that several focused intervention style programs intended to increase g in select groups had basically no effect. Most people in developed countries have access to these necessities, so it seems like further significant differentiation would be due to innate traits.

Please cite your sources for claiming fluid intelligence is not influenced by such interventions. This is not what I have seen. Especially where we are talking of early pre-K learning options.

3 hours ago, xenog123 said:

Assuming IQ is a valid measure of some property of the mind (brain), the historically measured gaps in IQ (and their measurement is basically factual) have persisted for so long and across so much societal change it seems difficult to imagine how they could be purely environmental in origin.

This is the fallacy of Argument from Incredulity. Many systemic biases have persisted long after legal/political remedies were put in place. See my comment about Appalachia. Long persisting lower scores there haven't led you or anyone else to posit a genetic lower intelligence in Scots-Irish and English ancestry. Hmm.

14 minutes ago, TheVat said:

I wasn't sure what xenog was short for,

xeno = alien, g = general intelligence. That's my working assumption.

16 minutes ago, TheVat said:

unless it was xenogenesis, as in the Octavia Butler novels. Which would be, at this point, ironic given Butler's ethnic origins.

Thanks for that little gem of knowledge. Though irony tends to go way over the heads of these people.

18 minutes ago, TheVat said:

Anyway, one can actually use your hillbilly reference to observe that no one has come up with a conjecture that rural folk of Scots-Irish descent in Appalachia have consistently shown lower IQ scores for many generations due to their ethnic origins. Funny how that works, eh?

Yes, very strange. But you have to admit, those odd little dances they do can be quite impressive. Natural rhythm?

3 hours ago, sethoflagos said:

4. You''re a bleached, inbred, hillbilly halfwit.

Go on, tell me why exactly you find that such an objectionable comment. I dare you.

Your username gives away exactly where you're coming from. A seriously low IQ error of judgment.

I don't care too much about your insults but what irks you about the username? It's just a random pseudonym.

EDIT: Oh missed the latest comment. Alien to intelligence, hilarious. Anyways if you have something actually useful to say you can go ahead, otherwise...

Edited November 29Nov 29 by xenog123

Okay. Let's have a look at your numbers.

On 11/27/2025 at 4:15 PM, xenog123 said:

Well one (I would think fairly obvious) explanatory factor for both of these cases would be selection bias. Whites in their native countries come from all backgrounds, while minority ethnic groups are more likely to be fairly recent immigrants who were selected from the higher strata of their home countries. So you're comparing the cream of the crop of Nigerian women (estimates for mean IQ of Nigeria range from 70 to 90) against the entire White American population.

I'm guessing you just pulled that estimate from where the sun doesn't shine, but let's run with 70, a full 2 SD below the (US?) average. So simply meeting par, the Nigerian American community must have been drawn from on or around the 97.5% mark on the IQ bell curve.

But since the 2nd generation exceed all others by some margin, they must either be ~15 points higher IQ than their parents (a possibility you have already rejected), or their parents were drawn from on or around the 99.85% mark on the Nigerian bell curve.

Now 0.15% of the Nigerian population 25 years ago would be about 170,000 individuals or about double the Nigerian American population.

So effectively, you're saying that the US immigration managed to lure half of the top 0.15% of the population to emigrate? From a country where top 1% of the country enjoy a standard of living in Nigeria far higher than anything they could afford in the US?

And how did they achieve this remarkable feat?

On 11/27/2025 at 5:34 PM, xenog123 said:

I mean it says right in that article that applicants have to meet some requirements for education, job training and work experience. There's also the self-selection factor, in that those who choose to apply are more ambitious, driven, higher IQ.

A selection process that correlates only weakly with IQ and would pass at least 10% of the population for lottery participation.

Your numbers fail at the first glance of real scrutiny.

As numbers made up in a dishonest attempt to justify deep prejudice always do.

2 hours ago, xenog123 said:

I don't care too much about your insults but what irks you about the username? It's just a random pseudonym.

LOL

1 hour ago, sethoflagos said:

Okay. Let's have a look at your numbers.

I'm guessing you just pulled that estimate from where the sun doesn't shine, but let's run with 70, a full 2 SD below the (US?) average. So simply meeting par, the Nigerian American community must have been drawn from on or around the 97.5% mark on the IQ bell curve.

But since the 2nd generation exceed all others by some margin, they must either be ~15 points higher IQ than their parents (a possibility you have already rejected), or their parents were drawn from on or around the 99.85% mark on the Nigerian bell curve.

Now 0.15% of the Nigerian population 25 years ago would be about 170,000 individuals or about double the Nigerian American population.

So effectively, you're saying that the US immigration managed to lure half of the top 0.15% of the population to emigrate? From a country where top 1% of the country enjoy a standard of living in Nigeria far higher than anything they could afford in the US?

And how did they achieve this remarkable feat?

A selection process that correlates only weakly with IQ and would pass at least 10% of the population for lottery participation.

Your numbers fail at the first glance of real scrutiny.

As numbers made up in a dishonest attempt to justify deep prejudice always do.

LOL

Well, a couple things.

1. The estimate of 70 to 90 was from a cursory search. 70 to me seems pretty low, I would guess the average is actually higher. So if you're taking the absolute lowest estimate the yes it might seem unrealistic.

2. Your math on the mean IQ of the migrant population doesn't make sense. You seem to think that a sample population with a mean IQ of 115 would have to be drawn from the proportion of the larger population that is above an IQ of 115, but that doesn't follow. If you're drawing a random sample from all those above 115 the mean of that sample will be > 115.

3. I wouldn't assume that IQ and SES correlate that tightly - there could be plenty of bright Nigerians from less affluent backgrounds.

4. I'm not sure about your stats on the size of the Nigerian American population - if the total population at a given date was some value, then it doesn't imply that that exact value immigrated all in that year. Presumably there would already have been some established migrants.

5. I think those qualifying characteristics you mentioned would filter out more than 10%. An IQ of 85 is already pretty low and that's the 15th percentile, I'd imagine most migrants would probably be at least average.

7 hours ago, TheVat said:

Anyway, one can actually use your hillbilly reference to observe that no one has come up with a conjecture that rural folk of Scots-Irish descent in Appalachia have consistently shown lower IQ scores for many generations due to their ethnic origins. Funny how that works, eh?

Well I don't know what anyone else has said about Appalachians but I would think genetics is a large factor in their low IQ - that particular sub-population was probably drawn from the lower proportion of the Scots-Irish distribution and has also been inbreeding for a while. It also wouldn't really be hypocritical to deny a genetic component anyways, since their environment is clearly impoverished.

I have been reading through this thread and think everyone in this thread should read Mihaly Csikszentmihalyi or Howard Gardner for a civil description of intelligence and creativity.

10 hours ago, xenog123 said:

Well, a couple things.

1. The estimate of 70 to 90 was from a cursory search. 70 to me seems pretty low, I would guess the average is actually higher. So if you're taking the absolute lowest estimate the yes it might seem unrealistic.

I have three young Nigerian nephews living in my Lagos apartment, and take an interest in their schoolwork. They go to quite a good school by Nigerian standards, but both their tuition and teaching materials fall short of those I received in an obscure Yorkshire farming village 60 years ago. And way short of those of my children. The Flynn Effect suggests that this 60-year+ lag will penalise them by oto 18 IQ points. So that figure of 70 is rather vital to your argument.

When I challenge it, you disown it and run away. Your dishonesty is clear for all to see.

10 hours ago, xenog123 said:

2. Your math on the mean IQ of the migrant population doesn't make sense. You seem to think that a sample population with a mean IQ of 115 would have to be drawn from the proportion of the larger population that is above an IQ of 115, but that doesn't follow. If you're drawing a random sample from all those above 115 the mean of that sample will be > 115.

It's a reasonable approximation when the gradient flattens out at the tail of the curve. To balance this, I deliberately omitted the detail that over 60% of the Nigerian population, dim and gifted alike, are below the age of 25 and therefore ineligible for the visa lottery. Your available 'pool of talent' is really only 0.06% of the population: ie less than the Nigerian American population.

11 hours ago, xenog123 said:

3. I wouldn't assume that IQ and SES correlate that tightly - there could be plenty of bright Nigerians from less affluent backgrounds.

I certainly wouldn't. But you're the one who claimed that these high IQ types were the ones with the drive and ambition to be successful in their endeavours. You can't have it both ways: and whichever you pick now will obliterate your own arguments elsewhere.

11 hours ago, xenog123 said:

4. I'm not sure about your stats on the size of the Nigerian American population - if the total population at a given date was some value, then it doesn't imply that that exact value immigrated all in that year. Presumably there would already have been some established migrants

Go argue your case with the US Census Bureau. The critical population under discussion is 2nd generation Nigerian Americans. Their parents must have emigrated from Nigeria roughly ten years either side of 2,000 when the total population was ~122 million. You're clutching at straws here.

11 hours ago, xenog123 said:

I think those qualifying characteristics you mentioned would filter out more than 10%. An IQ of 85 is already pretty low and that's the 15th percentile, I'd imagine most migrants would probably be at least average.

Learn to read. I credited your immigration process with filtering out up to 90% of applicants. Don't forget, I know quite a few people who emigrated under this scheme. Some quite closely. Such as my best ever junior process engineer. We still keep in touch.

11 hours ago, xenog123 said:

Well I don't know what anyone else has said about Appalachians but I would think genetics is a large factor in their low IQ - that particular sub-population was probably drawn from the lower proportion of the Scots-Irish distribution and has also been inbreeding for a while. It also wouldn't really be hypocritical to deny a genetic component anyways, since their environment is clearly impoverished.

As I said, irony wouldn't even give you a hair parting.

8 hours ago, sethoflagos said:

xeno = alien, g = general intelligence. That's my working assumption.

Thanks for that little gem of knowledge. Though irony tends to go way over the heads of these people.

Yes, very strange. But you have to admit, those odd little dances they do can be quite impressive. Natural rhythm?

1 hour ago, sethoflagos said:

I have three young Nigerian nephews living in my Lagos apartment, and take an interest in their schoolwork. They go to quite a good school by Nigerian standards, but both their tuition and teaching materials fall short of those I received in an obscure Yorkshire farming village 60 years ago. And way short of those of my children. The Flynn Effect suggests that this 60-year+ lag will penalise them by oto 18 IQ points. So that figure of 70 is rather vital to your argument.

When I challenge it, you disown it and run away. Your dishonesty is clear for all to see.

It's a reasonable approximation when the gradient flattens out at the tail of the curve. To balance this, I deliberately omitted the detail that over 60% of the Nigerian population, dim and gifted alike, are below the age of 25 and therefore ineligible for the visa lottery. Your available 'pool of talent' is really only 0.06% of the population: ie less than the Nigerian American population.

I certainly wouldn't. But you're the one who claimed that these high IQ types were the ones with the drive and ambition to be successful in their endeavours. You can't have it both ways: and whichever you pick now will obliterate your own arguments elsewhere.

Go argue your case with the US Census Bureau. The critical population under discussion is 2nd generation Nigerian Americans. Their parents must have emigrated from Nigeria roughly ten years either side of 2,000 when the total population was ~122 million. You're clutching at straws here.

Learn to read. I credited your immigration process with filtering out up to 90% of applicants. Don't forget, I know quite a few people who emigrated under this scheme. Some quite closely. Such as my best ever junior process engineer. We still keep in touch.

As I said, irony wouldn't even give you a hair parting.

Okay man I think I'm done splitting hairs with you - your analysis still has errors but we've strayed pretty far from the original point and I don't think it's worth wasting more time on this. You've also been insulting. Good day.

@xenog123
Donald ?!? ...
Is that you?

47 minutes ago, MigL said:

@xenog123
Donald ?!? ...
Is that you?

Man really.

The overlap in Venn diagram circles for racist and snowflake amazes me in its consistency.

6 hours ago, xenog123 said:

I would think genes set the upper limit on IQ and then environmental factors determine the rest.

We don't know that. As these things might co-develop it is difficult to figure out how one might put a boundary on the other.

6 hours ago, xenog123 said:

but still lower than that of his adopted family. If environment was purely the determining factor you'd think his IQ would rise to exactly that of the adoptees.

Again, no one claimed it was purely determined by the environment and you have ignored some of the early factors that can contribute to the further development. For example a telling study would be (as mentioned) a twin study with children form an affluent, highly developed household, split at some point after birth and one played into a developing country.

6 hours ago, xenog123 said:

As for what IQ measures the whole point is that it's supposed to be general intelligence,

That is not how IQ measurements were designed. Originally it was used to determine cognitive deficiencies. The g factor is a theoretical construct formulated by Spearman, as an assumed totality of general abilities. Essentially it was found that a lot of different tests would correlate with other, and the model was then, that there might be a common underlying factor (that might be connected to all of them). Pretty much from then on, there were discussion of which and how performance measures would correlate with g and why. Newer studies also found particular weaknesses as these models were built in a particular context and especially extremely different backgrounds (studies on San people were these measures just do not fit reality, as mentioned above- if they were so mentally deficient, why would they survive in such hostile environments for so long? ).

There were a few tests that were eventually developed to circle around the concept of the g factor, such as Raven's assessment which is often used as part of IQ tests. But again, for each there is a large body of lit discussing where and how they are applicable.

As a whole there is not clear unified method that assesses g, but a lot of different tests that are somehow associated and in contrast to a true biological trait like e.g. height, the g factor is a composite model that is in itself defined by test methods rather than a material basis.

There are there fore no clear mechanistic principles or even an objective or biological concept of g. That as a whole is in part why this area of research often is put under the soft sciences umbrella as we are dealing with correlates of concepts, rather something that we can isolate and measure directly (such as DNA sequences).

6 hours ago, TheVat said:

G comes from an interaction between many gene variants and the environment. The issue is whether genes are significant in differences in G between human groups.

I would go further and reiterate that definitions of g are much vaguer than what we would typically see in biology, where we look at physiological and phenotypic traits (and those associations can already be tricky- the height example you provided is a good one). One of the issues with Rushton is that in order to link IQ test measures to biology, he tried to pull in concepts like r and k selection strategy and apply to human populations. The issue here, of course is that with technical advances it became clear very rapidly that racial boundaries as set by him were not biologically verifiable and almost by definition differential selection in those groups would make even less sense.

On 11/29/2025 at 8:33 AM, TheVat said:

And heritability, whether low or high, implies nothing about modifiability. The classic example is height, which is strongly heritable (80 to 90 percent), yet the average height of 11-year-old boys in Japan has increased by more than 5 inches in the past 50 years. A similar historical change occurs for intelligence.

Good example, and there are more such as how heritability increases with socioeconomic status (I believe the author was Turkheimer and others, around 2000ish). The hypothesis was that at lower socioeconomic status environmental variability has a higher impact on the measures, but once a certain threshold is reached (where basically living standards become normalized) the measured variation is then more likely based on residual biology. From an experimental standpoint that makes a lot of sense, but also of course questions the ability of the tests to measure the "pure" biological basis.

But I think it is suffice to say that the field has enough uncertainty that strong assumptions are more likely than not to fall flat.

As for general intelligence being fixed, the OP has not considered neuroplasticity.

On 11/29/2025 at 9:48 AM, xenog123 said:

Your mind is your brain. Your brain is a part of your body. I don't see how you can deny that it is subject to genetic influence.

Again, you are missing the key point. There is genetic influence, for sure, but the brain has high plasticity and we do not know how interactions between genetics, environment and development interacts. The idea that some set of genes sets the gold bar for everything is simply not in line with how we understand physiology anymore. Moreover, it is possible that even in utero exposure is more critical than the genetic basis but the two would be almost impossible to disentangle (as you cannot test fetuses).

On 11/29/2025 at 9:48 AM, xenog123 said:

Assuming IQ is a valid measure of some property of the mind (brain), the historically measured gaps in IQ (and their measurement is basically factual) have persisted for so long and across so much societal change it seems difficult to imagine how they could be purely environmental in origin.

And yet folks have found that certain elements like literacy, vocabulary testing and so on have a huge impact on a wide range of IQ tests. They are not uniform nor as universal. They are stable in scoring withing a given population, but comparing between has been a long-standing debate. There are folks claiming universality, but it is by no measure the consensus. And as more studies were coming up, the more it has been questioned. In other words, the certainty you express is only shared by a smaller group of researchers and the evidence has been mounting against them for decades.

Just now, StringJunky said:

As for general intelligence being fixed, the OP has not considered neuroplasticity.

At this point, it looks more like ignoring than considering. After all, it has been mentioned a few times.

But I will point out how artificial this whole concept is. The tests are based mostly on forms of abstraction, many are non-verbal. These abilities are not well understood, and likely were elevated to that level of importance fairly recently in our evolutionary history. Yet the biological basis of whatever it is must be shared with our other abilities to function, such as identifying prey or dangers, solving immediate, practical problems and some level of planning ahead. The mere concept that some folks who are able to find solutions to survive and thrive in a hostile environment (as our ancestors did) are somehow mentally dysfunctional just makes no sense. Moreover, folks with e.g. Asperger's tend to score higher, especially in non-verbal tests and it is hard to argue that they perform better in complex environments.

1 minute ago, CharonY said:

Again, you are missing the key point. There is genetic influence, for sure, but the brain has high plasticity and we do not know how interactions between genetics, environment and development interacts. The idea that some set of genes sets the gold bar for everything is simply not in line with how we understand physiology anymore. Moreover, it is possible that even in utero exposure is more critical than the genetic basis but the two would be almost impossible to disentangle (as you cannot test fetuses).

And yet folks have found that certain elements like literacy, vocabulary testing and so on have a huge impact on a wide range of IQ tests. They are not uniform nor as universal. They are stable in scoring withing a given population, but comparing between has been a long-standing debate. There are folks claiming universality, but it is by no measure the consensus. And as more studies were coming up, the more it has been questioned. In other words, the certainty you express is only shared by a smaller group of researchers and the evidence has been mounting against them for decades.

At this point, it looks more like ignoring than considering. After all, it has been mentioned a few times.

Right. Missed that. I ask myself: Why try so hard to find a difference between ethnic groups when the only motive, I can think of, is to create division and conflict. All this effort when the noise floor clearly exceeds the level of the signal.

9 minutes ago, StringJunky said:

Right. Missed that. I ask myself: Why try so hard to find a difference between ethnic groups when the only motive, I can think of, is to create division and conflict. All this effort when the noise floor clearly exceeds the level of the signal.

In a way yes, but I will acknowledge that in the past that has been basically seen as a fact. The book/paper from Rushton and other had been highly influential in the 90s, and I recall some lectures that had those ideas baked in. As a biologist I was quit a fair bit dismayed and it was a minor reason why I switched from my initial interests towards genetics and related subjects.

31 minutes ago, CharonY said:

We don't know that. As these things might co-develop it is difficult to figure out how one might put a boundary on the other.

Again, no one claimed it was purely determined by the environment and you have ignored some of the early factors that can contribute to the further development. For example a telling study would be (as mentioned) a twin study with children form an affluent, highly developed household, split at some point after birth and one played into a developing country.

That is not how IQ measurements were designed. Originally it was used to determine cognitive deficiencies. The g factor is a theoretical construct formulated by Spearman, as an assumed totality of general abilities. Essentially it was found that a lot of different tests would correlate with other, and the model was then, that there might be a common underlying factor (that might be connected to all of them). Pretty much from then on, there were discussion of which and how performance measures would correlate with g and why. Newer studies also found particular weaknesses as these models were built in a particular context and especially extremely different backgrounds (studies on San people were these measures just do not fit reality, as mentioned above- if they were so mentally deficient, why would they survive in such hostile environments for so long? ).

There were a few tests that were eventually developed to circle around the concept of the g factor, such as Raven's assessment which is often used as part of IQ tests. But again, for each there is a large body of lit discussing where and how they are applicable.

As a whole there is not clear unified method that assesses g, but a lot of different tests that are somehow associated and in contrast to a true biological trait like e.g. height, the g factor is a composite model that is in itself defined by test methods rather than a material basis.

There are there fore no clear mechanistic principles or even an objective or biological concept of g. That as a whole is in part why this area of research often is put under the soft sciences umbrella as we are dealing with correlates of concepts, rather something that we can isolate and measure directly (such as DNA sequences).

I would go further and reiterate that definitions of g are much vaguer than what we would typically see in biology, where we look at physiological and phenotypic traits (and those associations can already be tricky- the height example you provided is a good one). One of the issues with Rushton is that in order to link IQ test measures to biology, he tried to pull in concepts like r and k selection strategy and apply to human populations. The issue here, of course is that with technical advances it became clear very rapidly that racial boundaries as set by him were not biologically verifiable and almost by definition differential selection in those groups would make even less sense.

Good example, and there are more such as how heritability increases with socioeconomic status (I believe the author was Turkheimer and others, around 2000ish). The hypothesis was that at lower socioeconomic status environmental variability has a higher impact on the measures, but once a certain threshold is reached (where basically living standards become normalized) the measured variation is then more likely based on residual biology. From an experimental standpoint that makes a lot of sense, but also of course questions the ability of the tests to measure the "pure" biological basis.

But I think it is suffice to say that the field has enough uncertainty that strong assumptions are more likely than not to fall flat.

27 minutes ago, CharonY said:

Again, you are missing the key point. There is genetic influence, for sure, but the brain has high plasticity and we do not know how interactions between genetics, environment and development interacts. The idea that some set of genes sets the gold bar for everything is simply not in line with how we understand physiology anymore. Moreover, it is possible that even in utero exposure is more critical than the genetic basis but the two would be almost impossible to disentangle (as you cannot test fetuses).

And yet folks have found that certain elements like literacy, vocabulary testing and so on have a huge impact on a wide range of IQ tests. They are not uniform nor as universal. They are stable in scoring withing a given population, but comparing between has been a long-standing debate. There are folks claiming universality, but it is by no measure the consensus. And as more studies were coming up, the more it has been questioned. In other words, the certainty you express is only shared by a smaller group of researchers and the evidence has been mounting against them for decades.

At this point, it looks more like ignoring than considering. After all, it has been mentioned a few times.

But I will point out how artificial this whole concept is. The tests are based mostly on forms of abstraction, many are non-verbal. These abilities are not well understood, and likely were elevated to that level of importance fairly recently in our evolutionary history. Yet the biological basis of whatever it is must be shared with our other abilities to function, such as identifying prey or dangers, solving immediate, practical problems and some level of planning ahead. The mere concept that some folks who are able to find solutions to survive and thrive in a hostile environment (as our ancestors did) are somehow mentally dysfunctional just makes no sense. Moreover, folks with e.g. Asperger's tend to score higher, especially in non-verbal tests and it is hard to argue that they perform better in complex environments.

So if you admit at least some genetic component to IQ, do you think that just determines baseline cognitive ability, and that through education/plasticity and equalizing environmental conditions everyone can in principle reach the same upper limit on human intelligence? I suppose that's possible, but consider the analogy to other physical traits/organs/system. Take something like muscle strength, for example. There are both genetic and environmental components to an individual's muscle power - proper nutrition and exercise can improve muscle development, and muscles can be said to be plastic in a sense. Yet clearly there is still an upper limit determined by one's genes - not everybody has the innate capacity to become a power-lifter, for example. The same could be said for other traits, like height, running speed, etc. So it seems like a pretty extreme case of exceptionalism to think that the brain, also a physical organ no more distinct from others, should be otherwise. It's not impossible of course, but...

It's true that IQ tests were not initially intended as measures of general cognitive ability, but they were pretty quickly adapted to that use, and it has been the consensus for quite a while that g is a highly useful/meaningful factor, whatever it actually is. If you're going to reject that by the same standards you might as well throw out all social sciences.

As for the idea of g being artificial or representing abstract abilities that don't correlate with practicality/survival, I think the fact that it is a good determiner of most mental functioning and correlates pretty highly with success in complex modern societies seems to imply it's not just some arcane construct only useful for book-learning. The counter examples you cited are kind of exceptional cases (the autistic savant types with high measured IQ but low practical sense or survivability, clearly a unique/deficient kind of phenotype) or the bush-folk that can survive in harsh environments despite their low IQ (again, a sponge with no brain can survive in places humans can't) that seem beside the point.

34 minutes ago, StringJunky said:

Right. Missed that. I ask myself: Why try so hard to find a difference between ethnic groups when the only motive, I can think of, is to create division and conflict. All this effort when the noise floor clearly exceeds the level of the signal.

Yeah that's a good point - why harp on about this at all. Like if this was your water cooler talk it'd be weird -"Oh hey Jamal, nice to see you. Hey, did you know that people of your ethnic background are statistically far less likely to pass a first year Calculus course? Well, see you at lunch." Anyways I gave my reasons for why its important in one of my earlier responses.

19 hours ago, xenog123 said:

So if you admit at least some genetic component to IQ,

It is weird to frame it as an admittance, as the discussion is about strong linkage of IQ to race, and it was never about whether there is any genetic basis. For a while the discussion has been heavily moving goalposts around, as the issue of building racial groups has not been addressed, nor whether the measures between groups are useful.

19 hours ago, xenog123 said:

he counter examples you cited are kind of exceptional cases (the autistic savant types with high measured IQ but low practical sense or survivability, clearly a unique/deficient kind of phenotype) or the bush-folk that can survive in harsh environments despite their low IQ (again, a sponge with no brain can survive in places humans can't) that seem beside the point.

Except of course, lifestyles like the San people have likely been part of our evolutionary history, whereas the ability to strive just by performing well in abstract tests is a new dev development. The former is more likely to leave signatures in our genome, rather than the recent events. But sure, if we declare everything that does not fit our narrative as beside the point, then the argument is iron clad. But it is also not worthy of discussion.

7 minutes ago, CharonY said:

Except of course, lifestyles like the San people have likely been part of our evolutionary history, whereas the ability to strive just by performing well in abstract tests is a new dev development. The former is more likely to leave signatures in our genome, rather than the recent events. But sure, if we declare everything that does not fit our narrative as beside the point, then the argument is iron clad. But it is also not worthy of discussion.

Not really sure what your point is - when you mentioned the San people initially I thought you were trying to argue that IQ is not the prime determining factor of survivability, but now it seems like you're trying to make the argument that abstract reasoning or general intelligence has been selected for only so recently that there hasn't been enough time for it to be encoded into genetic differences. What kind of timeline are you looking at there? I'd guess something like g has been selectable since as early as agrarian societies and the existence of spoken language and alphabets.