The notion that your genes are your essential self—genetic essentialism—is fairly recent. Although the idea that heredity contributes to our health and identity is ancient, the idea that for practical purposes it is all that matters dates only to the nineteenth century. The English statistician Francis Galton conceived of heredity as a subterranean stream of “germ plasm,” flowing down the generations, isolated and insulated from the environment’s buffeting of any individual body. In determining who we are, Galton wrote, nature was “far more important than nurture.”
That stream was increasingly polluted, Galton was convinced. Vexed by the fact that people paid more attention to breeding their cattle than themselves, in 1883 he proposed a scheme of hereditary improvement he called “eugenics,” meaning “well-born.” The stream of British germ plasm could be socially filtered, and even enriched, by persuading the “fittest” people (borrowing loosely from Darwin) to have more children; the “unfit,” fewer. A techno-optimist to the core, Galton believed that, given proper instruction, people would see the logic of this scheme and participate voluntarily.
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