The evidence is overwhelming in that direction:
Twin & family designs: h² ~0.4–0.8, often ~0.7–0.8 in adult samples like MISTRA.
Adoption: people resemble their biological relatives more than their adoptive relatives in IQ, despite strong environmental differences.
Molecular genetics: polygenic scores and GCTA show real, replicable genetic signal for intelligence.
What it does not mean is that:
1. IQ is fixed at birth in a way that cannot be influenced by environment.
2. IQ differences justify any sort of discrimination or moral ranking.
Those two points are where people tend to clutch their pearls and panic. Just because we have noticed an uncomfortable truth does not mean that it is valid to use it in a discriminatory manner; the issue becomes that people will inevitably do so, thus those "in power" cripple the theory in the crib so as to avoid the fearful and uncomfortable implications.
It's practically nobody's position that there's no linkage between genetics and intelligence (that would be weird indeed), but it's important for this comment for you to believe that's the counterargument --- otherwise the comment doesn't make sense.
If genetics is less than 5 percent I would consider that something worth ignoring.
If it is 10 percent it is substantial enough to make a difference at the extremes.
If it is 20 percent that is real serious business.
Anything higher means we should really sit up and take notice of this fact.
If you're arguing against a eugenicist then it's not just about the percentage, in that case you have to distinguish between genetic and heritable. Suppose that there are some set of four genes that, in just the right combination, are worth 5 IQ points. That's, by definition, genetic, but it won't have a strong correlation with heritability because every kid has four chances to get the combination wrong. Or, if the combination does something bad, four chances to get it right even if their parents didn't. So past performance is no guarantee of future results.
By contrast, if you're trying to decide whether to allocate more resources to kids who already show promise, you care about the individual's natural potential rather than the statistical probability that it will be similar to their parents, so it doesn't matter what was more likely, it matters what actually happened. And by the point you're performing the evaluation, you can't go back in time and change things like the prenatal environment for someone who is already born, so in that context those things belong in the "nature" column and "nurture" only gets the things you could still affect.
Let the science science, and policy makers make policy.
I think the problem comes when we want scientists to make policy recommendations.
I think scientists should help us determine what the facts are, not decide what to do about them.
What to do is for courts and democracy and for individuals to decide?
> 50% may sound like a solid heritability figure, but the associated correlation is rather modest.
Now the substance:
"The alleged “suppressed control group” does not turn the result into “no heritability”."
=> Of course not, did anyone claim there was no heritability? But
1/ It's not "alleged", it's printed black on white in the paper.
2/ There is no excuse for suppressing control group data (it's like suppressing the placebo arm of a drug study).
3/ It does turn the result into "junk", and it does establish a definite case of scientific malpractice among people arguing that IQ heritability is 0.70.
As for later analyses, they weren't the topic of my post, but that doesn't mean they're casher.
"I don't care if you find it fair. If you can't accept that genetics determines the entire organism (stress: entire) and does not stop at the neck, then you'd perceive my later criticisms as much worse than - gasp! oh great heavens! my pearls! - unfair. It is a bitter pill to swallow that some people were simply born with better hardware than yourself, one you are obviously railing against. Now, rush on and down vote this comment as well to lighten the burden of your cognitive dissonance. I'm also finding it difficult to reconcile your use of the flag/report on the parent comment versus the rules dictating and describing what is disallowed content. Disagreement is not against the rules. Perceived "fairness" is not in the rules."
Sorry to inform you that you don't understand the meaning of the verb "determine", as "genetics determines the entire organism" is scientifically wrong for obvious reasons: "influences", yes; "encodes proteins for", yes; but "determines", no.
And, no, I'm not railing against anyone's hardware as I'm pretty satisfied with mine.
"Whether or not you like MISTRA, “they left out the non-identical twins” is a side issue, and the broader evidence that IQ is substantially heritable is extremely strong.
Even if DZA were excluded, MZA alone provides a solid heritability estimate. The DZA sample was small and noisy, and MISTRA uses other twin and family data. Plus, meta-analyses confirm high IQ heritability, typically 0.5-0.8; Later structural-equation models applied to the full MISTRA cognitive dataset (MZA + DZA) estimated the heritability of general intelligence around 0.77, essentially the same ballpark as the original simple estimate. laplab.ucsd.edu. Intelligence is highly heritable, potentially reaching 80% in adulthood, supported by further studies like the Haworth et al. meta-analysis, showing age-related increases in heritability.
Strong evidence for polygenic and SNP heritability is shown from Plomin & von Stumm's 2018 research, showing how polygenic scores predict general intelligence.
Adoption studies further support the genetic influence, as adoptive siblings show weaker correlations compared to biological ones.
Environment is certainly NOT outweighed entirely or beyond merit, but evidence clearly shows the "uncomfortable" result having strong support despite desperate attempts to debunk.
In short; the op's story only works if including the DZA data actually drags the heritability estimate down into trivial territory. It does not.
Later analyses of the MISTRA sample that explicitly include both MZA and DZA twins and use full structural-equation models estimate heritability of general intelligence (g) at about 0.77 in adults. https://laplab.ucsd.edu/articles2/Lee2010.pdf
That is higher, if anything, than the original approximate 0.70. In other words:
The alleged “suppressed control group” does not turn the result into “no heritability”.
The more sophisticated models using that very same DZA data still say “IQ differences in this adult sample are heavily genetic.”
You just don't like this data, and don't want to accept it, because of the implications."
"For some people some subjects take on an irrational religious experience. Anything that is not a forceful agreement must be destroyed." Disagreement is not against the rules. Flagging a comment simply because you disagree with the content does appear to be against the rules, however, based on my reading.