Back when eugenics was all the rage.

Funny enough, even if racial purity wasn’t all the rage, and if they had the tools of modernity to determine whether a gene was associated with a trait instead of just “Welp, hopefully this isn’t just an expression of the environment (snip snip)”, eugenics of such a broad-spectrum application rarely works out because of the complexity of genes (and the long maturation time of human beings making resulting problems potentially unclear for decades). See: the many, many health problems of ‘purebred’ dog breeds.