Sanger’s eagerness to mainstream her movement explains her engagement with eugenics, a then widely popular intellectual movement that addressed the manner in which human intelligence and opportunity is determined by biological as well as environmental factors. Hard as it is to believe, eugenics was considered far more respectable than birth control. Like many well-intentioned reformers of this era, Sanger took away from Charles Darwin the essentially optimistic lesson that humanity’s evolution within the animal kingdom makes us all capable of improvement if only we apply the right tools. University presidents, physicians, scientists and public officials all embraced eugenics, in part because it held the promise that merit would replace fate — or birthright and social status — as the standard for mobility in a democratic society.

But eugenics also has some damning and today unfathomable legacies, such as a series of state laws upheld in 1927 by an eight-to-one progressive majority of the U.S. Supreme Court, including Justices Oliver Wendell Holmes and Louis Brandeis. Their landmark decision in Buck v. Bell authorized the compulsory sterilization of a poor young white woman with an illegitimate child on grounds of feeble mindedness that were never clearly established. This decision, incidentally, was endorsed by civil libertarians such as Roger Baldwin of the ACLU and W.E.B. Dubois of the NAACP, both of whom Sanger counted among her supporters and friends.