Why Biology Is Not Destiny

You must know the parable about the frog that sits in a pot of water being gradually heated, allowing itself to be boiled alive: because the change happens gradually, it never realizes it should leap out. Reading Kathryn Paige Harden’s book The Genetic Lottery: Why DNA Matters for Social Equality is a similar experience, as the author ingenuously points out. “Like a frog being slowly boiled alive,” she observes, readers follow her argument “from an uncontroversial premise to a highly controversial one.” Harden’s “uncontroversial premise” in this case is that siblings raised in the same family share a childhood environment and 50 percent of their DNA randomly assigned at conception, and are therefore like subjects in a controlled study of genetic differences. Ask anyone with a sibling whether their own childhood environment was the same as their sibling’s and you’ll quickly disprove Harden’s claim that her premise is uncontroversial. But putting that objection aside and sitting patiently as Harden increases the heat, we’ll arrive at her “highly controversial” assertion that “if siblings who differ genetically also have corresponding differences in...