Query: In what century did differences among human groups become a focus of science?
Context: The first post-Classical published classification of humans into distinct races seems to be François Bernier's Nouvelle division de la terre par les différents espèces ou races qui l'habitent ("New division of Earth by the different species or races which inhabit it"), published in 1684. In the 18th century the differences among human groups became a focus of scientific investigation. But the scientific classification of phenotypic variation was frequently coupled with racist ideas about innate predispositions of different groups, always attributing the most desirable features to the White, European race and arranging the other races along a continuum of progressively undesirable attributes.