THE current issue of the Yale Alumni Magazine includes a portrait of Irving Fisher, a Yale economics professor in the 1920s and ’30s and a giant of his field. The author, Richard Conniff, takes note of Fisher’s prodigious professional accomplishments and his private decency in order to foreground the real subject of his article: the economist’s role as one of his era’s highest-wattage proponents of eugenics.

The American elite’s pre-World War II commitment to breeding out the “unfit” — defined variously as racial minorities, low-I.Q. whites, the mentally and physically handicapped, and the criminally inclined — is a story that defies easy stereotypes about progress and enlightenment. On the one hand, these American eugenicists tended to be WASP grandees like Fisher — ivory-tower dwellers and privileged have-mores with an obvious incentive to invent spurious theories to justify their own position.

But these same eugenicists were often political and social liberals — advocates of social reform, partisans of science, critics of stasis and reaction. “They weren’t sinister characters out of some darkly lighted noir film about Nazi sympathizers,” Conniff writes of Fisher and his peers, “but environmentalists, peace activists, fitness buffs, healthy-living enthusiasts, inventors and family men.” From Teddy Roosevelt to the Planned Parenthood founder Margaret Sanger, fears about “race suicide” and “human weeds” were common among self-conscious progressives, who saw the quest for a better gene pool as of a piece with their broader dream of human advancement.

This progressive fascination with eugenics largely ended with World War II and the horrors wrought by National Socialism. But while the West has discarded the theory of the eugenics era, the practice urged by Fisher and others — the elimination or pre-emption, through careful reproductive planning, of the weaker members of the human species — has become a more realistic possibility than it ever was in the 1920s and ’30s.