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The genetic variants that raise intelligence also tend to pop up more frequently in people who have never smoked. Some of them also are found more often in peop
by cperciva 9y ago
The genetic variants that raise intelligence also tend to pop up more frequently in people who have never smoked. Some of them also are found more often in people who take up smoking but quit successfully.
The more we look, the more we're likely to find confounding genes like this. Sure, it might be that those genes directly raise intelligence... but it might also be that those genes make the parents less likely to smoke, and the measured difference in intellect is entirely due to exposure to parental smoking.
If there's a gene for "less likely to drop babies on their heads", it will probably show up as being correlated with higher intellect -- even if it has no direct effect on intellect and instead acts solely though yielding improved parenting.
- AlexCoventry 9y agoIf this study has captured anything beyond systematically correlated measurement errors (a problem which plagues high-throughput sequencing assays), it is almost certainly ancillary population substructure which correlates with socio-economic status.
- gwern 9y agoAlex, why do you say these hurtful things? You know perfectly well that they use principal components to successfully control away population structure, that the genetic correlations between cohorts are high, the hits replicate across populations, the enrichment sets and tissue expression are predominantly in the nervous system as expected, the polygenic scores are predictive of success even looking at just kids in poor families, and the within-family polygenic scores perform fine. No, it's not some measurement error on the several different SNP chips they used in the ~12 different cohorts or the entirely separate GWASes whose results they replicated, and it's definitely not 'residual population structure'. It was silly 4 years ago to write off GWAS results with that sort of logic, and it has only gotten sillier.
- theWatcher37 9y agoMan, that burn was orbital. Comments like these are why I come to HN
- Houshalter 9y ago>they use principal components to successfully control away population structure This sounds really interesting, how does that work exactly?
- gwern 9y agoNothing that special. You take the SNPs, extract the first 7 or whatever principal components, and include them in the regression. To the extent that there's some population structure and subgroups are smarter/richer, it'll get controlled away. No guarantee that it'll work, but it apparently does (probably because most of the structure is in the first few components and including PCs beyond that is harmless).
- johndevor 9y agoHow much of IQ do you think is correlated to genetics?
- sillysaurus3 9y agoIt's a politically-charged question, so people tend to be very careful to ensure that whatever they say is correct. It's probably difficult to give a convincing argument in the space of an average HN comment.
- berberous 9y agoIs linking genetics to intelligence politically-charged, or just linking race to intelligence?
- sillysaurus3 9y agoWhy not take a guess and see what happens?
- andrewprock 9y agoGiven that the definition of IQ is built upon constantly shifting sands, it's really hard to say.
- AlexCoventry 9y ago> ...even looking at just kids in poor families... At these sample sizes, that is an interesting idea. Has anyone checked?
- gwern 9y agoYes.
- virgilp 9y agoWith what results? No predictive value, in poor families? (also, do include some marker of sarcasm in your comments, it can get confusing)
- gwern 9y agoNo, of course they have predictive value. If they didn't, that would not support my point that the GWAS results are valid. The specific study I had in mind was "The Genetics of Success: How Single-Nucleotide Polymorphisms Associated With Educational Attainment Relate to Life-Course Development" https://www.gwern.net/docs/genetics/2016-belsky.pdf https://www.gwern.net/docs/genetics/2016-belsky.pdf , Belsky et al 2016.
- AlexCoventry 9y agoI apologize for misinterpreting your response as sarcastic. Why do you believe that PCA successfully captures all the relevant population structure? Probablistically, it's a Gaussian linear model... no reason to expect allele frequencies to follow that. If that were the case, methods like coalescent theory would be unnecessary. Why do you believe that high genetic correlations between cohorts is sufficient to ensure safe inference from GWAS meta analysis? These are tiny effect sizes, and the argument is essentially that the correlations with intelligence measurements are statistically significant. Unless you believe that your null model is an otherwise entirely accurate reflection of how the data is generated, of course you're going to see spuriously significant results in huge samples. I'll respond to your other points when/if I catch up on the literature. I'd be grateful if you could link the papers about the enrichment sets and tissue expression results.
- a_bonobo 9y ago>use principal components to successfully control away population structure PCA doesn't perfectly control away population structure, especially if you have cryptic tiny subpopulations in your dataset that only few individuals are in. In that case you don't have enough signal to establish the subpopulations. It's also a function of the way you call your SNPs - if you don't have enough SNPs, or focus on a different method, PCA won't magically know about those unobserved populations.
- theparanoid 9y agoThe most famous recent study used Iceland [0], which is about as homogeneous as you can imagine. [0] http://www.pnas.org/content/114/5/E727.full http://www.pnas.org/content/114/5/E727.full
- AlexCoventry 9y agoI'm pretty sure he was being sarcastic.
- nathan_f77 9y agoWow, I actually have no idea if gwern was being sarcastic or not. I didn't consider it until I read your comment. There's a few clues in there that do suggest sarcasm, but I really can't tell, because I know nothing about the field. I don't think they were being sarcastic though, because the rest of their replies are pretty serious.
- AlexCoventry 9y agoHe says some things with perfect confidence which are unknowable or false, but you do need a background in the field to see that. Also, he starts out with what seems to be an outrageous appeal to emotion, but I suppose "hurtful" could mean "harmful" rather than "mean."
- gwern 9y agoThey may not perfectly control, but they do the job well enough that the error from that is minimal and of less importance than other issues like limited SNP panel coverage, sample error, or measurement error (a _huge_ limit on current GWASes and very underappreciated, given how few papers attempt to correct for it or even mention what sort of psychometric properties the available data has). It is certainly not true, as Alex claims, that the results are nothing but systematic measurement error or population structure.
- sbierwagen 9y agoI feel like this is a distinction without a difference. We don't care about the anatomical structure of the brain, we care about measured intelligence, which correlates well with performance on a bunch of important things. You can hypothesize a gene that doubles your IQ, but also deletes your spinal cord, making it impossible to interact with the outside world/take IQ tests. Sure, your IQ is higher, but is it more useful? If your goal is to select for greater intelligence, then genes which prevent the carrier from smoking and dropping their offspring will increase intelligence, which is the point!
- skybrian 9y agoIf a gene decreases intelligence indirectly via nearsighted, it would be good to know that so you can get people glasses. (Or, actually, you don't really need to know about the genes in that case.)
- RichardHeart 9y agoTiming. Unique "Better baby raising" genes would make better baby's, however, those genes would help you less if you didn't make babies. Thus, Not all things that make smarter kids, make you smarter.
- pavement 9y agoThe counter-point being that you'll have people getting vanity tests, and harping on about their smart genes, even though none of them are the sort of gene that confers actual palpable intelligence. Some of these are not smart genes, if they still result in dimwitted people you'd hate to be trapped in a room with. They may be good genes that promote healthy survival, and statistically stongly correlated with smart people, but if they aren't the crucial genes that result in the sort of person that quickly grasps complex concepts, has nice handwriting and can keep up with high learning curves, then they are helpful health and survival genes, not intelligence genes.
- Sharlin 9y agoI don't think selection by Mendelian breeding is very relevant here. Direct autosomal genetic engineering is. Your designer baby is not going to get an intelligence boost if the gene you modify actually has an indirect confounding effect via a parent's phenotype.
- accountyaccount 9y agowoah looks like someone got the gene for "writing this specific internet post"
- phkahler 9y agoIt turns out people with schizophrenia are more likely to smoke because they feel that it helps their symptoms.