I want to know the answer to the following question:
In what century did differences among human groups become a focus of science?
All the background I'm provided with is that "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.". Is that enough to answer the question?
Answer: no