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Not all causes are treated equal

Over on Twitter the eminent population geneticist Molly Przeworski has an important and lauded thread up:

The thread has been widely re-tweeted and quote-tweeted by biologists. This prompted a response by a prominent sociologist, who quoted this from Kathryn Paige Harden’s discussion with Sam Harris:

What Harden is alluding to is that heritability within populations is not portable necessarily to between populations. In less sophisticated hands, this is almost used as an incantation. In my review of Harden’s book I said the following:

The biological reason that this extrapolation founders is that human populations differ, and those differences matter. The genetic architecture of intelligence may vary between populations so that predictions from the markers in one population are poorly predictive of variation in another, in line with the general concerns for GWAS portability…Harden points out correctly that population structure exhibits different layers of granularity and continuity. Perhaps a prediction trained on British samples is poorly predictive in Pakistanis. But what about Iranians? If it is poorly predictive in Iranians, what about in Bulgarians? The ability to infer within and between-group heritability is conditional on what you mean by “group,” and that is to some extent a subjective choice guided more by heuristics and instrumental utility than idealistic differences between races.

To be entirely frank I think Harden was on solid ground as a behavior geneticist with psychological training who relied on what population geneticists say publicly all the time about heritability and group differences. The issue is that I do not believe population geneticists were entirely candid about the deep texture of their assumptions, beliefs, and expectations. They wanted to be left alone to do their research, and so relied on a mantra to make people leave them alone, and now that mantra taken so literally is coming back to haunt them. One reason Prezworski’s thread got a lot of attention is privately this is the sort of intuition and sense that’s widely understood, but the issues are subtle, so to outsiders people just leave it off with the quick quips about portability. A friend told me “Molly doing this is like a goddess descending to Earth to speak to mere mortals so it will get a lot of attention.”

The real issue though is that some are now rather perturbed that Harden and behavior geneticists are trying to shield their study of psychological trait heritability from charges of racism by separating the discussion of between and within-group differences by implicitly reifying “population.” Additionally, some geneticists are quite unhappy at the discussion of heritability when it comes to psychological characteristics, so what was a convenient mantra to have people leave them alone is now coming back to haunt them, as it’s opening up avenues for research that they’re not comfortable with, are not interesting in, and believe are possibly dangerous. To be candid if I was Harden I’d be a bit peeved since all she’s doing is repeating what a lot of authorities in the field have been writing and saying for decades.

Nevertheless, if you take a look at the people who re-tweeted and commented on Przeworski’s thread it’s pretty much everyone. The high and mighty, all the way to the low. It was positively re-tweeted by people who are very skeptical of the study of heritability in psychological characteristics in humans (to be charitable). And, it was positively re-tweeted by me. Since so many people liked it and re-tweeted it, I can tell you it was re-tweeted by people who are actually quite open to and interested in the study of psychological characteristics in humans, within and between groups, without divulging confidence (I checked who commented and re-tweeted and liked).

So what’s going on? Prezworski’s group has published several papers in this area (for example, The evolution of group differences in changing environments), and one of the upshots for many is that there’s a lot less certainty about the heritability of many traits and its utility for polygenic risk scores even within groups because of uncorrected confounds. Some people took from this that polygenic risk scores are useless (not necessarily Prezworski and her group!). But when I talked about these findings with Amit Khera, who works on polygenic risk scores relating to cardiovascular disease, he was actually happy about these results. Why? Because he wanted to correct any confounds there were. He viewed these results not as a death knell for polygenic risk scores, but as a way to make them better, more accurate, more precise. He’s a medical doctor who is trying to help people in their health decisions. All he cares about is greater effectiveness. He’s not invested in a particular result, he’s invested in outcomes (OK, at least ideally, but I talked to him and his enthusiasm seemed genuine).

This is almost certainly why people who think polygenic risk scores are useful, and heritability in psychological characteristics are real, and vary widely in human populations, re-tweeted the Prezworski explainer. I myself did for this reason. My own current belief is there’s good evidence for heritability for a lot of behavioral traits, and that polygenic risk scores can be useful, at least on the margin. But we need to get better, and to do that, we need to explore all the subtle distinctions and details in relation to environmental and genetic variation. This is no guarantee. Perhaps the skeptics of polygenic risk scores will be correct (I doubt it, but who knows). But we’re not at the point where we can settle that question right now. More science needs to be done.

Finally, we need to address the magic of genes. People put a lot of stock in genes for various ideological reasons. But the reality is a lot of environmental factors taken for granted by many (e.g., shared home environment) are a lot less clear and well understood than genes are. And yet the skeptical takes don’t rain down on social science inferences and correlations. Mostly because they’re not seen as insidious because they’re environmental. But causes are causes. When there is a great deal of environmental variation in an outcome that doesn’t mean that you can control it, or you even know what it is. A lot of what is in the “E” in the ACE model is mysterious. Many focus on genes because they’re clear and distinct.

4 thoughts on “Not all causes are treated equal

  1. I read the New Yorker review of Harden’s book. I was pleasantly surprised that they were willing to take her seriously. I was less happy with the way that Charles Murray and conservatives in general were treated.

    As for Murray I have heard enough of his explanations of his work to be confident that liberals caricature it, But, I have not read enough to defend him. I will leave to others.

    What really annoyed me was his caricature of conservative thought: “because of course the right already cares about genes” “On her left are those inclined to insist that genes don’t really matter; on her right are those who suspect that genes are, in fact, the only things that matter.”

    Nonsense. I am not going to write a Milan post on the issue. A couple of quick points.

    Conservatives believe that human nature is always and everywhere the same. Human nature may well be genetic in origin, but it is is common to all men. It does not vary between groups, or even within groups.

  2. @Razib

    Off-topic, but as I understand, the Yamnaya are a mix of Eastern Hunter Gatherers and Caucasian Hunter Gatherers. So do we know if proto-proto-Indo European was spoken by EHG or CHG? And whether it was EHG or CHG who had R1a and R1b?

  3. But causes are causes. When there is a great deal of environmental variation in an outcome that doesn’t mean that you can control it, or you even know what it is.

    It is an exaggeration (but not a giant one) that the major project of university research since 1900 has been finding those environmental variations and controlling them to be better. Control requires a controller, thus the preference of most university people for a large and powerful government (run by university educated people).

    Discovering that environmental variations are not so important has been a tremendous blow and thus largely denied. Ditto for the ability of government to make a positive difference.

  4. It seems obvious to me that polygenic scores would not work the same in all lineages. For example, light skin color in East Asians is effected by different genes then skin coloring in Europeans. However that doesn’t really mean that the average distribution of skin color in the 2 populations is the same.
    Anyway, Charles Murray’s point is that if group A has lower average IQ then group B and that it is difficult to change that whether the reason is environmental or genetic then we can’t expect any plausible policy to change that fact. As a matter of fairness to group A, then, we need to ensure that our society produces paths that allow lower IQ people to flourish which will disproportionately help group A.

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