In the early 20th century, many anthropologists accepted and taught the belief that biologically distinct races were isomorphic with distinct linguistic, cultural, and social groups, while popularly applying that belief to the field of eugenics, in conjunction with a practice that is now called scientific racism. After the Nazi eugenics program, racial essentialism lost widespread popularity. Race anthropologists were pressured to acknowledge findings coming from studies of culture and population genetics, and to revise their conclusions about the sources of phenotypic variation. A significant number of modern anthropologists and biologists in the West came to view race as an invalid genetic or biological designation.