The Genetic Lottery: Why DNA Matters for Social Equality, by Kathryn Paige Harden, Princeton University Press, 312 pages, $29.95
"Luck," E.B. White once said, "is not something you can mention in the presence of self-made men." They worked hard, no doubt, to get where they are. But they also benefited enormously from good fortune, not just in life but in life's building blocks. A fortunate combination of thousands of slight genetic differences boosted their intelligence, motivation, openness to experience, task perseverance, executive function, and interpersonal skills.
"Like being born to a rich or poor family, being born with a certain set of genetic variants is the outcome of a lottery of birth," the behavioral geneticist Kathryn Paige Harden argues in The Genetic Lottery. "And, like social class, the outcome of the genetic lottery is a systemic force that matters for who gets more, and who gets less, of nearly everything we care about in society."
Harden's book can be divided into three parts. The first is an introduction to behavioral genetics, the science of how differences between individuals arise through the interaction of their genes and their environments. The second is an insightful critique of social science researchers who refuse to consider genes' effects, showing how this leads them astray when devising interventions to ameliorate social ills. And the third is an argument, light on details, that genetic inequality can "be used to make the case for greater redistribution of resources."
Behavioral geneticists construct polygenic indexes, numbers that summarize how the cumulative effects of small differences in genes contribute to complex traits. Those traits correlate with outcomes relevant to how well people's lives are likely to go, among them adult height, cardiovascular disease risks, physical strength, longevity, and—key to Harden's argument—educational attainment.
"In the US today, whether one is a member of the 'haves' or the 'have-nots' is increasingly a matter of whether or not one has a college degree," Harden writes. "If we can understand why some people go further in school than others do, it will illuminate our understanding of multiple inequalities in people's lives." Many people who do not go to college nonetheless make decent livings. But a recent analysis by Georgetown University's Center on Education and the Workforce found that the median lifetime income of college graduates in the U.S. is $2.8 million. For Americans who get only a high school diploma, it's $1.6 million.
Since 1970, Harden notes, rising percentages of U.S. students from each income quartile have been completing college degrees by age 24. But today 62 percent of students from the top income quartile finish college, while only 16 percent in the lowest quartile do. The results were similar in a 2018 study that constructed a polygenic index for educational attainment: Students whose polygenic indexes were in the top quarter of the distribution were nearly four times more likely to graduate from college than those in the bottom quarter.
Harden cites another study that found 27 percent of children with the lowest polygenic scores whose fathers' incomes were in the top quartile graduated from college, compared with 24 percent of children with the highest polygenic scores whose fathers' incomes were in the bottom quartile. "Poor childhood environments appear to squander the human potential of individuals with favorable genetic endowments by preventing access to increasingly lucrative educational pathways," the researchers concluded. So socioeconomic status clearly makes a significant difference too.
Harden has little patience with many progressives' notion that "we already know what to do" to improve lives and lessen social and economic inequalities. In fact, she writes, there is no "vast repertoire of policies and interventions that have been proven to be effective at addressing social inequalities in education and health and that are just waiting in the wings to be deployed, if we can only muster sufficient political will." Around 90 percent of the educational interventions evaluated by the Department of Education, for example, "produced weak or no positive effects."
Harden suggests that such interventions often fail because researchers are not taking into account the ways "genetic and environmental factors are braided together." A 1995 "word gap" study, for instance, found that poor children hear, on average, 30 million fewer words than kids from higher-income families do by age 3. This research had a huge impact: A scan of Google Scholar finds that it has been cited nearly 11,000 times by other studies. The Obama administration endorsed the findings in 2014, declaring that the gap "can lead to disparities not just in vocabulary size, but also in school readiness, long-term educational and health outcomes, earnings, and family stability even decades later." Governments have spent millions trying to close the gap.
Yet nearly every word-gap study ignores the fact that parents are genetically related to their children. Harden notes an exception: a 2016 study that found children in higher-income families also tended to have higher polygenic scores. Children with higher polygenic scores tended to say their first words at a younger age and were stronger readers by age 7, regardless of their families' socioeconomic status. (A recent article in Child Development challenged the word-gap studies' general validity: Its authors found that the number of words heard by young children is much greater when you count those spoken by all household members, and the differences were not predicted by family income.)
As Harden observes, many academics believe that "discussing genetic causes of social inequalities is fundamentally a racist, classist, eugenic project." One colleague told her that conducting research on genetics and education made her "no better than a Holocaust denier." But parsing genetic differences need not lead to pernicious eugenic conclusions.
Eugenics, Harden explains, "asserts that there is a hierarchy of superior and inferior human beings, where one's DNA determines one's intrinsic worth and rank in the hierarchy." Such reasoning was used to justify compulsory sterilization laws in 32 states during the 20th century; more than 60,000 Americans were involuntarily sterilized as a result. As the philosopher Elizabeth Anderson has observed, "People, not nature, are responsible for turning the natural diversity of human beings into oppressive hierarchies."
Just as most people are apt to think sleep when they hear bed, Harden notes, Americans too often think race when they hear genes. She rightly rejects racist notions about population differences: "It's wrong to assume that research on the genetic causes of individual differences within a population gives us information on the causes of group differences." She points out that most polygenic scores have been developed among individuals of European ancestry and thus have limited generalizability across other populations.
Indeed, Harden argues that the "science of human individual differences is entirely compatible with a full-throated egalitarianism." She asks, "Why are inequalities that are related to your genes more acceptable than inequalities rooted in the social circumstances of your birth?" After all, "Both are accidents of birth, forms of luck over which a person has no control."
Then Harden offers her thoughts on how to apply insights from behavioral genetics to create a more equal society. She relies chiefly on the philosopher John Rawls' notion of the "difference principle," according to which social and economic inequalities are just if they are arranged so that they provide the greatest benefits to the least advantaged members of society. In Harden's words, "Society should be structured to work to the advantage of the people who are least advantaged in the genetic lottery."
Harden acknowledges that the last two centuries have seen "enormous gains in life span, literacy, wealth, [and] well-being that ultimately worked to everyone's advantage." From 1820 to 1992, she notes, global average per capita incomes grew eightfold, and the share of people living in extreme poverty dropped from 84 percent to 24 percent. (Updating her figures to 2018, global per capita incomes had risen tenfold since 1820 and extreme poverty had fallen to less than 9 percent.) How did this happen? Harden mentions "innovations in science, technology, and government." But she concedes that some of these innovations were "inequality-dependent"—that is, "they were made possible by a system that differentially rewarded different types of skills."
In Rawls' conception of a just society, the "greatest equal liberty principle" takes priority over the difference principle. "Each person has an equal right to a fully adequate scheme of equal basic liberties which is compatible with a similar scheme of liberties for all," he argued. And in fact, institutions of liberty are the most effective way to harness human beings' natural diversity to the goals of reducing poverty, increasing literacy, raising life expectancy, and otherwise improving the world. The current income distribution in rich developed countries may not be strictly in line with Rawls' difference principle, but the lives of the least advantaged have substantially improved in modern market societies.
Inequalities imposed by governments, such as Jim Crow, are evil and must be eliminated. But once such government shackles are removed, people incentivized by free markets have the opportunity to improve their lots from wherever they begin their lives. Each of us is responsible for making the best of the different hands dealt us by our genes and upbringings. The good fortune to have been born into a liberal market society is far more salient than the luck of either social class or genetic endowments.