I think Steve Hsu has written some about the evidence for additivity on his blog (Information Processing). He also talks about it a bit in section 3.1 of this paper.
So I only briefly read through the section of the paper, but not really sure whether it applies to my hypothesis: My hypothesis isn’t about there being gene-combinations that are useful which were selected for, but just about there being gene-combinations that coincidentally work better without there being strong selection pressure for those to quickly rise to fixation. (Also yeah for simpler properties like how much milk is produced I’d expect a much larger share of the variance to come from genes which have individual contributions. Also for selection-based eugenics the main relevant thing are the genes which have individual contribution. (Though if we have precise ability to do gene editing we might be able to do better and see how to tune the hyperparameters to fit well together.))
Please let me know whether I’m missing something though.
(There might be a sorta annoying analysis one could do to test my hypothesis: On my hypothesis the correlation between the intelligence of very intelligent parents and their children would be even a bit less than on the just-independent-mutations hypothesis, because very intelligent people likely also got lucky in how their gene variants work together but those properties would unlikely to all be passed along and end up dominant.)
To clarify in case I’m misunderstanding, the effects are additive among the genes explaining the part of the IQ variance which we can so far explain, and we count that as evidence that for the remaining genetically caused IQ variance the effects will also be additive?
I didn’t look into how the data analysis in the studies was done, but on my default guess this generalization does not work well / the additivity on the currently identified SNPs isn’t significant counterevidence for my hyptohesis:
I’d imagine that studies just correlated individual gene variants with IQ and thereby found gene variants that have independent effects on intelligence. Or did they also look at pairwise or triplet gene-variant combinations and correlated those with IQ? (There would be quite a lot of pairs, and I’m not be sure whether the current datasets are large enough to robustly identify the combinations that really have good/bad effects from false positives.)
One would of course expect that the effects of the gene variants which have independent effects on IQ are additive.
But overall, except if the studies did look for higher-order IQ correlations, the fact that the IQ variance we can explain so far comes from genes which have independent effects isn’t significant evidence for the remaining genetically-caused IQ variation also comes from gene variants which have independent effects, because we were bound to much rather find the genes which do have independent effects.
(I think the above should be sufficient explanation of what I think but here’s an example to clarify my hypothesis:
Suppose gene A has variants A1 and A2 and gene B has B1 and B2. Suppose that A1 can work well with B1 and A2 with B2, but the other interactions don’t fit together that well (like badly tuned hyperparameters) and result in lower intelligence.
When we only look at e.g. A1 and A2, none is independently better than the other—they are uncorrelated to IQ. Studies would need to look at combinations of variants to see that e.g. A1+B1 has slight positive correlation with intelligence—and I’m doubting whether studies did that (and whether we have sufficient data to see the signal among the combinatorical explosion of possibilities), and it would be helpful if someone clarified to me briefly how studies did the data analysis. )
@towards_keeperhood yes this is correct. Most research seems to show ~80% of effects are additive.
Genes are actually simpler than most people tend to think
I think Steve Hsu has written some about the evidence for additivity on his blog (Information Processing). He also talks about it a bit in section 3.1 of this paper.
Thanks.
So I only briefly read through the section of the paper, but not really sure whether it applies to my hypothesis: My hypothesis isn’t about there being gene-combinations that are useful which were selected for, but just about there being gene-combinations that coincidentally work better without there being strong selection pressure for those to quickly rise to fixation.
(Also yeah for simpler properties like how much milk is produced I’d expect a much larger share of the variance to come from genes which have individual contributions. Also for selection-based eugenics the main relevant thing are the genes which have individual contribution. (Though if we have precise ability to do gene editing we might be able to do better and see how to tune the hyperparameters to fit well together.))
Please let me know whether I’m missing something though.
(There might be a sorta annoying analysis one could do to test my hypothesis: On my hypothesis the correlation between the intelligence of very intelligent parents and their children would be even a bit less than on the just-independent-mutations hypothesis, because very intelligent people likely also got lucky in how their gene variants work together but those properties would unlikely to all be passed along and end up dominant.)
Thanks for confirming.
To clarify in case I’m misunderstanding, the effects are additive among the genes explaining the part of the IQ variance which we can so far explain, and we count that as evidence that for the remaining genetically caused IQ variance the effects will also be additive?
I didn’t look into how the data analysis in the studies was done, but on my default guess this generalization does not work well / the additivity on the currently identified SNPs isn’t significant counterevidence for my hyptohesis:
I’d imagine that studies just correlated individual gene variants with IQ and thereby found gene variants that have independent effects on intelligence. Or did they also look at pairwise or triplet gene-variant combinations and correlated those with IQ? (There would be quite a lot of pairs, and I’m not be sure whether the current datasets are large enough to robustly identify the combinations that really have good/bad effects from false positives.)
One would of course expect that the effects of the gene variants which have independent effects on IQ are additive.
But overall, except if the studies did look for higher-order IQ correlations, the fact that the IQ variance we can explain so far comes from genes which have independent effects isn’t significant evidence for the remaining genetically-caused IQ variation also comes from gene variants which have independent effects, because we were bound to much rather find the genes which do have independent effects.
(I think the above should be sufficient explanation of what I think but here’s an example to clarify my hypothesis:
Suppose gene A has variants A1 and A2 and gene B has B1 and B2. Suppose that A1 can work well with B1 and A2 with B2, but the other interactions don’t fit together that well (like badly tuned hyperparameters) and result in lower intelligence.
When we only look at e.g. A1 and A2, none is independently better than the other—they are uncorrelated to IQ. Studies would need to look at combinations of variants to see that e.g. A1+B1 has slight positive correlation with intelligence—and I’m doubting whether studies did that (and whether we have sufficient data to see the signal among the combinatorical explosion of possibilities), and it would be helpful if someone clarified to me briefly how studies did the data analysis.
)