“Eugenics,” we are told in this disquieting documentary, “is the dream of a measurable man.” The tools that drive this dream are not the yardstick and caliper, but shaky science turned toward faulty ends. Peter Cohen's sobering history of the eugenics movement reveals a malign cult of human improvement. Unlike fads that promote stronger bodies, smarter minds, better looks, all relatively benign and superficial enhancements, eugenics, especially when coupled with a political agenda, has grave implications that reach far beyond the fate of individuals. Francis Galton fathered the term in the nineteenth century, advocating breeding among superior beings, while discouraging those of inferior comportment from breeding at all. This dualistic notion persisted for decades, as Cohen shows in a pastiche of forbidding archival images. Much has been said of the Nazis' use of eugenics as a means for Aryan ascension, but little is known of the vogue for similar theories in the United States, often masquerading as oddball sociopolitical theory. It's clear that the eugenic impulse isn't extinct-it's just a recessive trait waiting for the right genomic turn of events.