Do genes play a role in cognitive traits like shyness, memory, language skills, and so forth? Of course they do. The only real question is how big a role they play. Take language, for example. In the case of which language you speak, the role of genes is 0%. It's all environmental. But in the case of how well you speak a language, it's much higher.
This is obvious enough that it should be uncontroversial, and it would be except for one thing: if genes have an effect on cognitive traits, it means that genes have an effect on the trait we call intelligence. And if genes affect intelligence, then it's possible that racial differences in intelligence are partly the result of genetic factors.
The fear that this could be true, even though the evidence is currently against it, has driven left-wing opposition to the whole notion of genes and behavior for decades. Luckily for everyone involved, the evidence for the impact of genes is based almost solely on ecological studies, usually of twins. But no matter how suggestive such studies can be, they will never be proof positive of anything. The only thing that has a chance proving anything is biochemical: that is, finding specific gene complexes that affect personality traits. That's basically impossible, which meant everyone could keep merrily arguing forever, safe in the knowledge that no one would ever be conclusively proven wrong.
But lots of things are impossible until suddenly they aren't. Readers with very good memories may recall that a few years ago I wrote about Genome Wide Association Studies (GWAS, pronounced jee-wass). These do the impossible: they allow genetic researchers to find single-nucleotide polymorphisms (SNPs, pronounced snips) that are associated with cognitive traits. At the time, I linked to a paper that claimed to have found SNPs that explained about 5% of the variance in intelligence. But work was ongoing, and the latest studies have gotten up to 20% or so. There's no telling where this number will eventually end up, but it's almost certain that within a few years we'll get to one that's high enough to prove to all but the most recalcitrant that genes do in fact have a considerable effect on human intelligence.
Why mention this? Because in its current issue the New Yorker has a profile of Kathryn Paige Harden, a professor of psychology at the University of Texas at Austin who has written a new book, The Genetic Lottery: Why DNA Matters for Social Equality. Harden has been doing GWAS work of her own and her conclusion is unsurprising: both genes and environment play significant and intertwined roles in most cognitive traits. But there's a depressing coda:
In my conversations with her colleagues, Harden’s overarching idea was almost universally described as both beautiful and hopelessly quixotic....James Tabery, a philosopher at the University of Utah, believes that underscoring genetic difference is just as likely to increase inequality as to reduce it. “It’s truly noble for Paige to make the case for why we might think of biological differences as similar to socially constructed differences, but you’re bumping into a great deal of historical, economic, political, and philosophical momentum—and it’s dangerous, no matter how noble her intentions are, because once the ideas are out there they’re going to get digested the way they’re going to get digested,” he said. “The playing board has been set for some time.”
"Hopelessly quixotic" is a fancy way of saying that no matter what the science says, Harden will never convince people on the left. As Harden puts it, the life of a behavior geneticist resembles “Groundhog Day.” Always the same arguments no matter what.
In fairness, the reason for lefty intolerance of cognitive genetics is obvious and righteous: It's been violently misused for a very long time as a way of proving that certain kinds of people are inferior to others. As Tabery says above, the playing board has been set, and it's almost certain that any new results, no matter how carefully explained, will be used as an excuse by some people to dismiss the possibility of ever improving the lives of the poor, the black, and the oppressed.
But as understandable as this is, it has a big problem: it looks as if we're getting close to a genuine understanding of how genes affect cognitive traits—and the answer is not going be "they don't." At that point the left had better have an argument to make, because they're certain to lose if they just bury their heads in the sand.
The funny thing is that I've never entirely understood lefty opposition to the notion that genes have a significant impact on cognitive abilities. My view has always been close to Harden's: if genes do have an impact, then it makes the case for social safety nets incomparably stronger. It becomes impossible to argue, for example, that poor people are merely lazy if you can point to SNPs that have a clear association with poverty. At that point, it's provably the case that being poor is mostly a matter of bad genetic luck. So what argument is left for leaving anyone in poverty?
Beyond that, as Harden points out, if you know the genetic foundations for a particular trait then it's easier to disentangle its genetic and environmental causes. This makes it easier to accurately identify the environmental causes, which in turn makes it more likely that you can construct social interventions that actually work. In other words, knowledge of genetics is a key part of the liberal project of doing everything we can to improve lives via social programs that are truly effective.
But most people don't see it that way. And beneath it all lurks the deep fear that someone doing GWAS research is eventually going to find SNPs associated with both race and intelligence. I continue to think that's unlikely in anything more than a trivial sense, but I may be wrong. And if I am, what are we going to do?
Just because you have the brain of a pyschopath doesn't mean you have to grow up to be one:
https://www.theguardian.com/commentisfree/2014/jun/03/how-i-discovered-i-have-the-brain-of-a-psychopath
It sometimes does. Most of the time the techniques can successfully develop them into a functioning member of society... but not with every kid.
There’s still an implicit assumption that race X will have lower or higher amounts of trait Y. The Left’s wariness is based on that assumption. The Right’s confidence certainly does!
But even if you can nail down “race” (can all East or West Asians, Africans, etc, really homogenous with no admixtures? Can the “one drop” theory really apply at the genetic level?) there will always be massive overlaps. See height, need for glasses, etc.
And not to put too fine a point on it but genes or no genes, in my own family my boomer generation has had more lead poisoning than my parents or children, and you can see it in multiple assessments of intelligence.
So…
I agree that it’s worth pursuing looking at intelligence markers, but sheetingly stupid to limit the search to racial groups. And equally stupid to assume even at the individual level that genes are destiny.
Not accusing you of making either claim. But I’d be way more comfortable with your stance if you were more clear about those two particular points.
It's already quite clear from the genetic information available that the Big Three (or whatever variation on that 19th century schema) are not genetically coherent and e.g within Africa where genetic diversity is highest, you'd need to have at least several 'races' (that is structured genetic populations).
Of course it's plausible there are sub-populations that have predominance of some not great genes for any given trait - but on the Continental level of the old races it's pure bollocks as they're coherent populations.
The idea that highly mixed American populations with Eurasian, Amerindian branch-off of Euraisan genes plus a total mix of African somehow got sub-human gene sets is pure bollocks as well
However the racialists can't let go of 19c ideas.
Hmm. I’m from the deep south and there are always jokes floating around about the lower average IQ. There’s no doubt that many of the very brightest and most motivated leave for greater challenges and rewards, but that shouldn’t have more than a marginal effect overall. My own experience was in a high-school class of roughly a hundred kids, with a good 13 or 14 who tested into the honors/gifted/talented program, which IIRC required an IQ score of 120. What I’ve found most interesting, though, is that the brighter kids who either moved out of state or to a college town environment are almost always more curious, more interested in a variety of topics, and more verbally adept than the equally intelligent kids who stayed local. I guess some of it is selection bias, but it’s kinda weird to hear fellow expats say “I can’t even have a conversation with anyone back home any more.” By all appearances, environment can actually make smart people dumber.
There is a long history of scientists acting in good faith, putting forward ideas or concepts that could be used for social good, only for the ideas to be used for regressive and negative things. Hell, evolution itself led to social Darwinism. I think the idea that genetic linked intelligence would lead to a greater sensitivity and stronger safety net is naive isn’t he extreme.
It would lead to stronger discrimination and more social Darwinism.
Eventually we could get this to an individual level. You would definitely have a scientific way to create castes, abandon teaching the "dumb" as a waste beyond the basics and focus your attention on the smart ones. So what would happen is we'd develop the alpha beta etc. society from Brave New World.
Mostly the issue is agency.
If you are inferior should you be allowed to pass on those genes? Should they be allowed to have a say in government?
I agree that the tangle begins with agency.
Justice Thomas has already talked about how the effect of legal abortions is effectively eugenic, especially in the case of Down's Syndrome, and that's enough for him to link them morally. That is, terminating a pregnancy because you know that the fetus has trisomy 21 is equivalent to Nazism.
Of course, that ignores lots of other factors. Down's Syndrome runs that gamut from mild to severe, and parents' circumstances (and ability to handle a child with Down's Syndrome) vary widely.
If a marker for autism is found out soon, watch out.
The naivete in your third & second to last paragraphs would be easier to understand if you hadn't been writing about American politics for the last two decades. Really, just appalling.
Your characterization - "the trait we call intelligence" - is inaccurate. The term intelligence does not refer to a single trait; it's always a bundle of traits, inclinations, and abilities.
And this isn't a left/right issue except for this: right-wingers will seize upon any shred of scientific evidence to justify racism & sexism. Even if that shred of evidence is later proved to be questionable or even fabricated, it will still be used to justify or excuse racism and sexism. Damn, Kevin, look around you at the anti-vaccine movement.
And this isn't a left objection, it's a human rights objection.
Intelligence may be a bunch of traits, but in the public mind it can be represented by a single number, and therefore is effectively one trait.
I fully expect Baseball Knower & Epidemiologist Nate Silver to embrace that one number the same way the Baseball Analytics Community has embraced OPS+.
& as we know from the Houston Astros front office (2012-19), nothing bad ever came of that.
You don't need right wingers for racism and sexism. They are inheritance themselves. Left wingers racist and sexist were the norm and expected. Women were collective property. Nonwhite, capitalist scabs.
Maybe the degree of human intelligence can be measured (although so far I don't think it has) and linked to specific genes. But the way the brain works, with its billions of neurons and the infinite unique connections each brain makes causes me to think there will never be a definitive measurement of how intelligent one person (or race) is compared to another. There are just too many variables. In simplest terms, one person with an IQ of 160 might excel at math but not biology. If she happens to choose a career in biology (and she can, because she's so smart), that Nobel prize in math will never be granted.
The idea that this measurement and genomic linkage is just around the corner goes into my self-driving-car file for now.
"Maybe the degree of human intelligence can be measured (although so far I don't think it has)"
There is a whole field of study that says otherwise.
"one person with an IQ of 160 might excel at math but not biology"
It doesn't work that way. There is a g-factor, meaning a general intelligence factor, that results in people with high IQs having high aptitude in general. So a person with an IQ of 160 who excels in math can also excel in biology if they put their mind to it.
Are you Loq Qabin Republiqan Nate Silver's burner?
Whatever. I am just stating points known within the mainstream science.
FOAD, you racist troll. Charles Murray is not 'mainstream science'.
Yeah....
Linus Pauling was a brilliant scientist who went off the deep end concerning mega-doses of vitamin C.
With climate change and now with the pandemic, you'll get intelligent scientist from other fields (typically physicists?) reporting or trying to publish studies that are at best naive, though usually bonkers. Not sure where that falls in the measure of IQ--using ones' intelligence to rationalize away real and inconvenient data. That doesn't mean there can't be true cross disciplinary work--but that usually takes very gifted people in the right situations.
There are smart people who could do well no matter what path they end up on, to a point--but to be great, it has to be their passion. And being strong in math is not a guarantee that one will be just as strong in languages.
Sorry, but IQ does measure intelligence. The concepts and methods have been stable for years. And the g factor is a widely accepted concept regarding intelligence. I am just stating the mainstream science.
Sigh. Read Gould's The Mismeasure of Man for a lesson in the misuse of statistics and general statistical ignorance this almost certainly implies.
I sincerely doubt you have the g-factor to understand the arguments the way I do. But you should at least make the attempt, amirite?
G-factor is statistical artefact and your extrapolation here is generally bollocks.
G-factor is a variable that summarizes positive correlations among different cognitive tasks. It reflects the fact that an individual's performance on one type of cognitive task tends to be comparable to that person's performance on other kinds of cognitive tasks.
The g factor is not a physical thing in the brain. Instead it's just a useful construct.
Don't know much about statistics, do you troll. And once again, your assertion that what Charles Murray's pushing is 'mainstream science' is just so much crap.
Now go away, troll.
Science is relentless and today has no borders. The Chinese/Russians/Japanese etc have no hang ups about finding the genetic basis of intelligence and using it to better their position in the world. If it exists, it will be found somewhere and commercialized.
If science turns out to be not what one hoped it would be, there is no opt out; we have to deal with it. As a progressive committed to universal human rights, the possibility (and it is only that) of a proven modest racial component to intelligence doesn't scare me. I believe it would necessarily be slight compared to the overall human range, with very substantial overlap across races, and a much greater environmental component to effective individual intelligence, as compared to genetic. I doubt that there would be any justifiable public policy difference between a no-ethnic-difference world and a "modest difference" one. There could indeed be a political problem, but we could handle that, and would need to.
Sometimes I wonder if we have this collective disconnect between accepting we are the product of evolution yet free of the effects of selection.
“ It becomes impossible to argue, for example, that poor people are merely lazy if you can point to SNPs that have a clear association with poverty. At that point, it's provably the case that poverty is mostly a matter of bad luck. So what argument is left for leaving anyone in poverty?”
Wow, is this a hopelessly naive argument. Historical enslavement was based on the idea of inherent inferiority. People would go right back to making the same arguments.
Why stop at slavery?
I think liquidation is more likely.
Slavery in the ancient world seems to have been a matter of luck. If you lost a war, you might get enslaved. The intelligence of some slaves was recognized and they got important duties - just not their freedom. The racial aspect became important as agriculture in the New World needed people to work in the fields and as Europe conquered Africa. Perceptions of supposed racial superiority/inferiority seem to have greatly increased at that time.
Sometimes I wonder if we have this collective disconnect between accepting humans are the product of evolution yet free of the effects of selection.
Not sure how this ended up being posted twice. Apologies.
What we call intelligence is the product of a physical organ, the brain. Why wouldn't our genetics have some effect on the attributes of that part of our bodies?
Nevertheless, the association of cognitive ability with specific genetic traits opens the door to deeper discrimination in a couple of ways I can think of:
"It's genetic--no amount of intervention will matter." Programs that counteract the environmental disadvantages of poverty will face steeper opposition as opponents argue that the programs can't overcome genetic predetermination.
"People with defective genetics are a drain on society." Yeah, this is a eugenicist's wet dream--a "scientific" measure of who is worthy and who isn't. As others in the comments have implied, so-called genetic intelligence isn't the lone quantity that gives a life value.
What if the science is rock solid and irrefutable and it determines that whites are the least intelligent people on earth?
Any such results would be decried as ideologically biased pseudoscience, or--more likely--suppressed and never reported.
It would be ascribed to kancellation kulture come to hard science akademia, the Nazi-Left having finally achieved its goal of revenge for the settlement of the British American colonies, displacement of the Indigenous, & capture of the African as free labor.
Ever notice that it's the folks who let on as they're pretty intelligent are exactly the same people who believe in a single innate score 'IQ'?
Ever notice that this is strongly correlated with not being the sharpest knife in the block? Dunning-Kruger strikes again.
The threading in this comment section is not clear. Are you replying to me? If so, you may have misread me. My earlier comment should clear things up.
I should have included "@ScentofViolets" in my comment.
This is a reply to ProgressOne, noted neanderthal and trog. Amazing how these people are oblivious to the fact they've blown themselves up and in a single sentence have lost all credibility.
@ScentofViolets
The threading in this comment section is not clear. Are you replying to me? If so, you may have misread me. My earlier comment should clear things up:
https://jabberwocking.com/the-intelligence-wars-may-soon-come-to-an-end/comment-page-1/#comment-29233
I don't think anyone can reasonably argue that genetics has no impact on intelligence. The controversy is if "race" has an impact on intelligence. And it truly makes you wonder why some people are so eager to prove that it does. It's as if people are researching the relationship between race and dancing ability or greediness.
If genetics had no impact on intelligence, you could teach an ant calculus. Eventually. Somehow I don't think that's the argument most of those on the 'environmental' side is making.
I worked 10 years at IBM...and saw (mostly) men of incredible intelligence that had the common sense, wit or empathy of a toaster oven...and acted like they were gods. Like beauty, IQ can give people the delusion that they are special; in one aspect they may be...and yet be miserable monsters.
“ At that point, it's provably the case that poverty is mostly a matter of bad luck. So what argument is left for leaving anyone in poverty?”
…….
“Undeserving people” will remain “undeserving people” no matter the reason for their situation. Society should be helping those who are down on their luck because they are human beings, not just because “oh NOW they gave a good reason for being down on their luck.”
Science should go ahead and continue this field of study if it wants. But new discoveries in genes won’t change a thing if our hearts don’t change.
What it really means is they may be able to develop treatments for some, or all, kinds of deficient IQs.
We are expecting Flowers for Algernon, but we get Flowers for Charlie.
There are actually several questions involved here. The main ones are whether intelligence is hereditary at all, and whether there are racial differences.
The evidence that intelligence is heritable is very strong. For one thing, if it is not then the high intelligence of humans would have to have arisen by some other process than Darwinian natural selection. Is there not an intelligence difference between humans and other apes and is this not heritable and an advantage for humans? Many actual studies have shown heritability of intelligence in humans. This is somewhat confused by the artificially high values obtained from separated-twin studies, some of which may have been partially falsified, but all serious studies find considerable heritability. This inevitably leaves open the possibility of eugenics. Animal breeders select for various qualities and obtain striking results in periods of dozens of years, for example with dog breeds. The qualities which are selected for include behavioral characteristics which we would call intelligence. Society just has to decide whether eugenics is permissible on a societal or even private level (abort a child with Down syndrome?). Genetic analysis is not necessary for eugenics - people who test for low intelligence as children would just not be allowed to breed.
Whether there are racial differences is much harder to pin down, but if there are differences they are much smaller than indicated by "intelligence" tests. You certainly can't predict people's intelligence from their color. But if differences are found the same moral questions have to be faced.
Apparently Down Syndrome is not heritable so this is not a case of eugenics, but other things affecting mental capability could be heritable and detectable with DNA analysis.
What's going to be interesting is seeing how the various SNPs that code for more intelligence or less intelligence are distributed across populations. If the prevalence of the SNPs are roughly the same between Blacks and Whites (or whatever populations you care about), then the idea that genetics can explain differences between groups is disproven.
Frankly, I find the whole project of trying to distinguish traits at the population level distasteful in the extreme. What matters is the total of genetics and environment for individuals. There are plenty of really, really smart Black people, and plenty of really, really dumb white people. Is this person in front of me in the smart group our the dumb group? That's all I care about.
So, GATTACA was a forward-looking documentary? …
"if you know the genetic foundation for a particular trait then it's easier to disentangle its genetic and environmental causes"
I agree with this, but I'm not sure KD has thought through the implications.
In his recent book, "Facing Reality", Charles Murray makes the point that social scientists, when studying inequality, should be correcting results for IQ differences among groups. This makes sense to me whether IQ differences are due purely to environmental reasons, or due to a mix of environment and genes. I've wondered in the past about this same point that Murray makes. I've looked for studies that do this, but couldn't find any reputable ones. Researchers will correct for education, social class, and so on - but it appears they avoid correcting for IQ. My guess is that they want to avoid the risk of career damage.
Think of the potential implications of correcting for IQ in studies of inequality. Suddenly black-white income differences go away. In many areas - like educational outcomes, heath incomes, etc. - IQ differences likely explain most of the inequality/inequity. The underpinnings for the major claim by the social-justice left today - that the US is a white supremacist society built around systemic racism - begins to unravel. People really aren't ready for this.
Hear that everyone? ProgressOne reads the works of noted racist Charles Murray.
Of course he does. Ignorant little fucker isn't he?
As I have asked you before, please never comment on things I write.
FOAD, you racist troll. I used to have some small sympathy for the drivel you posted as merely being uninformed and unable to tell a good argument from a bad one. Thanks for relieving me of that small obligation.
Now get out of here. And don't come back.
In John McWhorter's review of Murray's book he writes the following paragraphs:
He is also one of America’s most brilliant thinkers.
To many familiar with Murray’s work, I have already revealed myself as a “racist” in engaging his work at all, and/or not calling him one.
However, Murray’s work is too carefully reasoned and too deeply founded on scholarly sources to be dismissed as “racist,” except by people whose definition of “racist” is “That which people of the black American race don’t like for any reason.”
Rather: I salute Murray’s brilliance while being disturbed by many of his arguments. What many will call racism is what I call being able to walk and chew gum at the same time.
Is this like how I admire “Triumph of the Will”?
Hitler and the Nazis learned about eugenics from the American "progressives" of the early 20th century. Is this what you are referring to?
(Of course, after the horrors of WWII, nearly all people on the left dropped their support for eugenics.)
@progressone .. and judging from the events of this year, the Republicans, big supporters of hitler before the us entered the war, never lost their admiration for fascism.
No, everything is built on Jewish led debt expansion and its relation to science, which was very "IndoEuropean" in its recent evolution. "Social Justice" is really turned anti-leftist in reality.
Certainly, genetics may affect cognitive abilities, but I think it goes too far to claim that it leads to greater or lesser "intelligence", especially between ethnicities. Intelligence involves many capabilities - pattern recognition, spacial awareness, memory, creative and critical thinking, and many more. Does this come through in ethnic differences? Maybe - it does in physical differences. Some ethnicities appear to have a different genetic bias toward fast- or slow-twitch muscle fibers, for example, leading one population to produce great sprinters and another to produce great distance runners and a third to be the source of the best weightlifters (at least at the olympian extremes - average folks from each group might beat one another regardless of their supposed ethnic specialty). It makes sense to think some populations might tend towards excellence in different mental skills . It's dangerous to equate that with "intelligence" per se, or to turn small differences in performance at the extremes into prejudices that define an entire population. It's also inadvisable to rank the different mental abilities above one another - each has value in proper context, and a successful group will demonstrate strengths in different skills, provided by different individuals.
Another point is that between widely separated populations there may be different genes that boost intelligence that are absent anywhere else but which will add up to the same effects, as there are different genes that code for blond hair in Europeans and Melanesians.
Oh come on, how can this have come up yet again?
"Intelligence" -- however it is defined -- is a product of both "nurture" and "nature." There are people who are naturally more "intelligent" -- or if you prefer, "gifted" or "talented" -- by nature than others. Consider great musicians, if you buy into the "seven intelligences" model: there are people who simply have more "musical intelligence" than others. And at the same time, "nurture" -- childhood environment, schooling and training, social environment, nature of daily work/activity, etc. -- has a huge effect on how intelligence develops: someone who might benefit greatly from formal schooling but is denied it from childhood on almost certainly will not be considered as "intelligent" as someone who by nature will benefit a little less but nevertheless receives and uses it.
It's both. And the contribution of "nurture" is large enough that, except perhaps for the most extreme cases of "nature" -- the truly tiny number of amazing geniuses who simply can't be stopped, or the tiny number of really unintelligent people who can only get so far no matter how well they're trained -- genes are not destiny. People with limited natural ability can and do go very far, and people with great natural ability can stagnate or never develop. Consider athletic ability: it's simply not the case that people who, say, win Olympic medals were destined to do so from birth. Training matters hugely.
Conclusion: all the genetic work in the world will never determine how "intelligent" someone turns out. Anyone who uses such an assertion as a premise for any kind of policy is either badly confused or seriously dishonest.
I need to read ALL the comments before I do.
Poverty Saps the Brain's Mental Reserves,
http://www.livescience.com/39297-poverty-saps-brains-cognitive-ability.html
Do people argue that genes can't affect intelligence? I thought that was accepted. What people argue with is the attempt to assign genetic differences to the concept of "race", like there is some pure "race" that is going to have higher intelligence than other "races".
You got it one, down to the scare quotes.
Yes, some people do argue that intelligence is not heritable, which is the critical thing. I came across a book in the library in which the author argued that heritability of intelligence is zero. In fact there is unreasoning opposition to any suggestion that differences in intelligence among races could arise, as Kevin says. There has been unending argument about the heritability value obtained from separated-twin studies, which don't really pertain to racial differences (you can't change the race of twins if you separate them, so they are still subject to environmental differences (discrimination) imposed because of race. But knowing that intelligence is heritable is a far cry from proof that there are racial differences.
I've often mentioned that many, if not most, social conservatives have never in their lives had anyone to speak to who isn't also a complete idiot, and that social conservatives tend to isolate themselves from non-social conservatives, and that they all but universally seem to broadcast on all frequencies and receive on none.
Surrounded by people who do nothing but blather strenuously for it's own sake it's no wonder they don't trust any actual source of information.
Having a good listener improves your brain health,
https://www.sciencedaily.com/releases/2021/08/210816112101.htm
Indeed, it's abundantly clear from many Scientifically Objective And Irrefutable Measures -- numbers of four-year and advanced degrees granted, average and median annual incomes, numbers of artistic awards, etc. -- that social conservatives are not as Intelligent as other people. The social policy implications are therefore equally clear: society should stop wasting resources on social conservatives and their communities -- no more highways or communication lines, no more federal or state facilities or installations, no more grants or loans to individuals or businesses, no other subsidies or price supports, no more waste of any kind on those people. As genetic inferiors, they simply don't deserve it.
Intelligence doesn't alter your traits, it just adds more detail to them.
and social conservatives will often complain that no one listens to them, which only proceeds to them keeping it up with still greater vehemence.
Ok, what is intelligence? The fundamental conceit of IQ tests is that a single number can represent something meaningful. Some people can easily pick up languages, even into adulthood. Some can play any instrument. Some excel at math or physics or.... Some are great at memorizing facts. Some have excellent spatial recognition. A few a true polymaths. And I didn't get into relating to people.
It's the same for great athletes. Some are great swimmers. Some runners. Etc. I wouldn't expect a swimmer to be a great marathoner, but both can be great athletes in their own way. And just because someone could have been a great athlete doesn't mean they will be a great athlete--they need access to training and facilities, esp. in their formative years. Some can overcome that, but not all.
If eugenics were every adopted by a totalitarian government, different traits could be selected for different populations. The proletariat could be selected for physical strength and ability to work long hours and a docile disposition. The elite could be selected for higher "intelligence" - that is whatever they choose to put in the tests. Some earlier dystopian novels had this.
As I said in an earlier comment, this does not really require DNA analysis, nor does it really require a precise definition of intelligence - only designing tests that bring out the desired qualities for the population being selected - or just somehow being able to perceive the differences. Animal breeder have been doing this for thousands of your, developing breeds with different useful qualities.
What we call intelligence - what an IQ test measures - is behavior, not any physiological quality.
It's like measuring height with a vertical jump and reach test. It's correlated, for sure, but it isn't the same as measuring a physiological characteristic.
We don't know what "intelligence" even is, physiologically. Are there more neurons? (I'm pretty sure that's a definitive "no"). Do the neurons fire faster, does the brain have a higher "clock speed"? Do synapses change more readily, to facilitate faster learning? Is it something else?
Even if we identify a genome or a region of DNA that seems to affect intelligence, the question then is "how does it affect intelligence? What is the mechanism?"
We are so very much in the dark here, as pertains to intelligence, but we often proceed as if we know all about it, and it explains everything.
It doesn't explain everything. Lewis Terman was deeply disappointed by how little it explained.
Genome Wide Association Reviews (GWAR) was right there.
Do better, Modernday Frankensteins.