Here is a good, very comprehensive introduction by Scott Alexander to the debate about missing heritability. This post is much shorter and is going to just focus on one aspect — the value of polygenic scores.
I think you cannot really talk about the magnitude/value of an effect size without first explaining what you intend to use it for. There are rare variants explaining a tiny amount of population variance but providing very important information for drug targets (which can then explain a large amount of population variance when intervened on). On the other hand, a smoking polygenic score might explain a decent amount of variance in lung cancer risk but will be useless in a model that already includes smoking itself. What is the intended use of the PGS? A lot of the existing applications in behavior genetics want to have a "clean" causal instrument, and the population PGS is clearly not that (and, I would argue, confounded in ways can be extremely misleading).
The more general point I'd make is that if a field describes a trait with 80% heritability (like height) as "largely genetic" then it should describe a trait with 10-20% heritability (like IQ is shaping up to be and Edu already is) as "largely non-genetic". That's just being consistent.
Yup, I agree. I didn't want to go off into that here, but it is worth another post.
About "largely genetic" vs "largely non-genetic". Broadly, sure, but be careful. Suppose we halve the number of questions in an IQ test. The IQ test now has more noise in it, and heritability drops accordingly. Has it become "more non-genetic"? Only in the sense of containing more randomness! The underlying thing we are trying to measure hasn't changed at all. Again, this is a problem with the heritability statistic. Non-heritability includes everything from systematic environmental variation, which the social scientist can in principle discover, to subtle obscure effects which might be hard to capture systematically, to pure noise, which is just not ever gonna be accounted for by anything.
So, it might be simultaneously true that a trait is only 10% heritable, and that _all_ its systematic variation comes from genetics; there is simply nothing else there to discover, and nothing else that we can target if we want to change it. Calling that "largely non-genetic" would be misleading, I think.
Specifically about EA, if you accept the numbers for the effect of polygenic scores in sibling regressions, then the relevant comparison isn't "everything else including noise" - it is other systematic environmental effects. ChatGPT gives some useful examples: https://chatgpt.com/share/68651971-9e04-8010-bed9-f664b4ebfc7f
What you see there is that there are some environmental effects with the same size as moving from the 5th to the 95th percentile of the EA PGS. But they are intensive: things like high-quality preschool (if that replicates) or cash rewards for completion (but you might worry about perverse incentives). Other effects, like small class sizes, or better teachers, are much smaller, unless you implement them over many years.
The point isn't that we should all be investing in embryo selection. Just that a fair statement is "genetic effects on education are big and substantive, as big as the biggest environmental effects we know about".
I think you cannot really talk about the magnitude/value of an effect size without first explaining what you intend to use it for. There are rare variants explaining a tiny amount of population variance but providing very important information for drug targets (which can then explain a large amount of population variance when intervened on). On the other hand, a smoking polygenic score might explain a decent amount of variance in lung cancer risk but will be useless in a model that already includes smoking itself. What is the intended use of the PGS? A lot of the existing applications in behavior genetics want to have a "clean" causal instrument, and the population PGS is clearly not that (and, I would argue, confounded in ways can be extremely misleading).
The more general point I'd make is that if a field describes a trait with 80% heritability (like height) as "largely genetic" then it should describe a trait with 10-20% heritability (like IQ is shaping up to be and Edu already is) as "largely non-genetic". That's just being consistent.
Yup, I agree. I didn't want to go off into that here, but it is worth another post.
About "largely genetic" vs "largely non-genetic". Broadly, sure, but be careful. Suppose we halve the number of questions in an IQ test. The IQ test now has more noise in it, and heritability drops accordingly. Has it become "more non-genetic"? Only in the sense of containing more randomness! The underlying thing we are trying to measure hasn't changed at all. Again, this is a problem with the heritability statistic. Non-heritability includes everything from systematic environmental variation, which the social scientist can in principle discover, to subtle obscure effects which might be hard to capture systematically, to pure noise, which is just not ever gonna be accounted for by anything.
So, it might be simultaneously true that a trait is only 10% heritable, and that _all_ its systematic variation comes from genetics; there is simply nothing else there to discover, and nothing else that we can target if we want to change it. Calling that "largely non-genetic" would be misleading, I think.
Specifically about EA, if you accept the numbers for the effect of polygenic scores in sibling regressions, then the relevant comparison isn't "everything else including noise" - it is other systematic environmental effects. ChatGPT gives some useful examples: https://chatgpt.com/share/68651971-9e04-8010-bed9-f664b4ebfc7f
What you see there is that there are some environmental effects with the same size as moving from the 5th to the 95th percentile of the EA PGS. But they are intensive: things like high-quality preschool (if that replicates) or cash rewards for completion (but you might worry about perverse incentives). Other effects, like small class sizes, or better teachers, are much smaller, unless you implement them over many years.
The point isn't that we should all be investing in embryo selection. Just that a fair statement is "genetic effects on education are big and substantive, as big as the biggest environmental effects we know about".