The earliest uses of the term "degeneration" can be found in the writings of Blumenbach and Buffon at the end of the 18th century, when these early writers on natural history considered scientific approaches to the human species. With the taxonomic mind-set of natural historians, they drew attention to the different ethnic groupings of mankind, and raised general enquiries about their relationships, with the idea that racial groupings could be explained by environmental effects on a common ancestral stock. This pre-Darwinian belief in the heritability of acquired characteristics does not accord with modern genetics. An alternative view of the multiple origins of different racial groups, called "polygenic theories", was also rejected by Charles Darwin, who favored explanations in terms of differential geographic migrations from a single, probably African, population.