As members of one species, we humans share both a common biology (cut us and we bleed) and common behaviors (we similarly sense the world around us, use language, and produce and protect children). Our human genes help explain our kinship—our shared human nature. And they contribute to our individual diversity: Some people, compared with others, are taller, smarter, skinnier, healthier, more temperamental, shyer, more athletic . . . the list goes on and on.
Across generations, your ancestors shuffled their gene decks, leading to the hand that—with no credit or blame due you—you were dealt. If you are reading this, it’s likely that genetic luck contributed to your having above average intelligence. Others, dealt a different hand and a different life, would struggle to understand these words.
Individual variation is big. Individuals vary much, much more within groups (say, comparing Danes with Danes or Kenyans with Kenyans) than between groups (as when comparing Danes and Kenyans). Yet there are also group differences. Given this reality (some groups struggle more in school), does behavior genetic science validate ethnocentric beliefs and counter efforts to create a just and equal society? In The Genetic Lottery: Why DNA Matters for Social Equality, University of Texas behavior geneticist Kathryn Paige Harden answers an emphatic no. She documents the power of genes, but also makes the case for an egalitarian culture in which everyone thrives.
Among her conclusions are these:
- We all are family. Going back far enough in time to somewhere between 5000 and 2000 B.C., we reach a remarkable point where “everyone alive then, if they left any descendants at all, was a common ancestor of everyone alive now.” We are all kin beneath the skin.
- We’re each highly improbable people. “Each pair of parents could produce over 70 trillion genetically unique offspring.” If you like yourself, count yourself fortunate.
- Most genes have tiny effects. Ignore talk of a single “gay gene” or “smart gene.” The human traits we care about, including our personality, mental health, intelligence, longevity, and sexual orientation “are influenced by many (very, very, very many) genetic variants, each of which contributes only a tiny drop of water to the swimming pool of genes that make a difference.”
- Individual genes’ tiny effects may nevertheless add up to big effects. Today’s Genome Wide Association Studies (GWAS) measure millions of genome elements and correlate each with an observed trait (phenotype). The resulting miniscule correlations from thousands of genetic variants often “add up to meaningful differences between people.” Among the White American high school students in one large study, only 11 percent of those who had the lowest GWAS polygenic index score predicting school success later graduated from college, as did 55 percent of those who had the highest score. “That kind of gap—a fivefold increase in the rate of college graduation—is anything but trivial.”
- Twin studies confirm big genetic effects. “After fifty years and more than 1 million twins, the overwhelming conclusion is that when people inherit different genes, their lives turn out differently.”
- Parent-child correlations come with no causal arrows. If the children of well-spoken parents who read to them have larger vocabularies, the correlation could be environmental, or genetic, or some interactive combination of the two.
- Beware the ecological fallacy (jumping from one data level to another). Genetic contributions to individual differences within groups (such as among White American high school students) provide zero evidence of genetic differences between groups.
- Genetic science does not explain social inequalities. Harden quotes sociologist Christopher Jencks’ illustration of a genetically influenced trait eliciting an environmentally caused outcome: “If, for example, a nation refuses to send children with red hair to school, the genes that cause red hair can be said to lower reading scores.” Harden also quotes social scientist Ben Domingue: “Genetics are a useful mechanism for understanding why people from relatively similar backgrounds end up different. . . . But genetics is a poor tool for understanding why people from manifestly different starting points don’t end up the same.”
- Many progressives affirm some genetic influences on individual traits. For example, unlike some conservatives who may see sexual orientation as a moral choice, progressives more often understand sexual orientation as a genetically influenced natural disposition.
- Differences ≠ deficits. “The problem to be fixed is society’s recalcitrant unwillingness to arrange itself in ways that allow everyone, regardless of which genetic variants they inherit, to participate fully in the social and economic life of [their] country.” An example: For neurodiverse individuals, the question is how to design environments that match their skills.
- Behavior genetics should be anti-eugenic. Advocates of eugenics have implied that traits are fixed due to genetic influences, and may therefore deny the value of social interventions. Alternatively, some genome-blind advocates shun behavior genetics science that could inform both our self-understanding and public policy. Harden advocates a third option, an anti-eugenic perspective that, she says, would reduce the waste of time and resources on well-meaning but ineffective programs. For example, by controlling for genetic differences with a GWAS measure, researchers can more accurately confirm the actual benefits of an environmental intervention such as an educational initiative or income support. Anti-eugenics also, she contends,
- uses genetic information to improve lives, not classify people,
- uses genetic information to promote equity, not exclusion,
- doesn’t mistake being lucky in a Western capitalist society for being “good” or deserving, and
- considers what policies people would favor if they didn’t know who they would be.
Harden’s bottom line: Acknowledging the realities of human diversity, and discerning the powers and limits of various environmental interventions, can enhance our quest for a just and fair society.
(For David Myers’ other essays on psychological science and everyday life, visit TalkPsych.com. Follow him on Twitter: @davidgmyers.)
