The Genetic Lottery

Why DNA Matters for Social Equality

by Kathryn Paige Harden


Harden’s thesis has two parts: first, that genetic effects on one’s life trajectory are meaningful; second, that considering these effects is necessary to make a more just and equitable society. She also spends about 10% of the book attacking eugenicists for being eugenicists, which is always fun.
Look, for example, at the extensive FAQ written by the Social Science Genetics Association Consortium to accompany the publication of their 2018 GWAS of educational attainment. It was extremely pessimistic about using an education-associated polygenic index for “any practical response”, because the index is “not sufficient to assess risk for any specific individual.” The only application they did endorse? “The results of our study may be useful to social scientists, e.g., by allowing them to construct polygenic scores that can be used as control variables.
A GWAS (Genome-Wide Association Study) assesses individual gene correlation with trait representation in a population. Because most traits we care about (“intelligence”, insofar as it can be well-defined, “mental disorders”, “executive function”) are likely extremely polygenic, such tests only start to pick up statistically significant influences with large sample sizes (the individual effect size of any single gene is tiny). Nevertheless, these have been conducted, and with >10^6 participants these studies have started to bear fruit.
If you put all the genes identified in the GWAS together in the form of a polygenic index, you can account for ~13 percent of the variance in educational attainment. This is substantial when viewed in comparison to the effect sizes that we see for other social science variables (e.g., 11 percent for family income). Yet it is still a far cry from the twin study estimate that about 40 percent of the variation in educational attainment is due to genes.
Generally, genetic influences estimated by GWASes are less than those implied by twin studies. Two reasons why: GWASes underestimate genetic influence (more genes have even smaller effects that in aggregate account for more differences) and twin studies overestimate it (identical twins are assumed to have equivalent environments). But even as a lower bound, GWASes imply that, holding all else equal, varying one’s genome has at least as much influence as being born to college-educated parents, being born in a two-parent household, or being born into a richer family.

In the past few years, the field of psychology has been rocked by a “replication crisis,” in which it has become clear that many of the field’s splashy findings, published in the top journals, could not be reproduced and are likely to be false. Writing about the methodological practices that led to the mass production of illusory findings (practices known as “p-hacking”), the psychologist Joseph Simmons and his colleagues wrote that “everyone knew [p-hacking] was wrong, but they thought it was wrong the way it is wrong to jaywalk.” Really, however, “it was wrong the way it is wrong to rob a bank.”

Like p-hacking, the tacit collusion in some areas of the social science to ignore genetic differences between people is not wrong in the way that jaywalking is wrong. Researchers are not taking a victimless shortcut by ignoring something (genetics) that is only marginally relevant to their work. It’s wrong in the way that robbing banks is wrong. It’s stealing. It’s stealing people’s time when researchers work to churn out critically flawed scientific papers, and other researchers chase false leads that will go nowhere. It’s stealing people’s money when taxpayers and private foundations support policies premised on the shakiest of causal foundations. Failing to take genetics seriously is a scientific practice that pervasively undermines our stated goal of understanding society so that we can improve it.

Does this mean that inequalities in society are inherent and can only be changed with mass gene drives? Harden argues no, that in fact the fitness of a given gene is dependent on the environment in which the organism expresses it, and just like we can treat nearsightedness with eyeglasses we can treat other genetic predispositions with environmental interventions. (Obviously this is correct). But failing to account for genetic influences (using polygenic scores as a “control variable”) will likely lead to the development of ineffective interventions as our metrics won’t account for inherent confounders.

I think this is broadly correct. Important to note that as far as I can tell, the only GWASes with statistically significant results have been done on those with European ancestry. Given that information, it’s definitely incorrect to generalize that a major contributing factor to racial inequalities in education/income/wealth have a genetic component (we just don’t have data), but it is evidence that on an individual level, holding all else equal, your genes matter.

And why should we treat this any differently from other factors we judge one to have no control over? We can’t choose our parents or our birthplace. We couldn’t choose our genes either, and they might matter more.

Random facts that I’m confused about: