In the years following Buffon's death, the theory of degeneration gained a number of new followers, many of whom were concentrated in German-speaking lands. The anatomist and naturalist Johann Friedrich Blumenbach praised Buffon in his lectures at the University of Göttingen. He adopted Buffon's theory of degeneration in his dissertation "De Generis Humani Varietate Nativa". The central premise of this work was that all of mankind belonged to the same species. Blumenbach believed that a multitude of factors, including climate, air, and the strength of the sun, promoted degeneration and resulted in external differences between human beings. However, he also asserted that these changes could easily be undone and, thus, did not constitute the basis for speciation. In the essay “Über Menschen-Rassen und Schweine-Rassen,” Blumenbach clarified his understanding of the relationship between different human races by calling upon the example of the pig. He contended that, if the domestic pig and the wild boar were seen as belonging to the same species, then different humans, regardless of skin color or height, must too belong to the same species. For Blumenbach, all people of the world existed as different gradations on a spectrum. Nevertheless, the third edition of "De Generis Humani Varietate Nativa", published in 1795, is famed among scholars for its introduction of a system of racial classification which divided humans into members of the Caucasian, Ethiopian, Mongolian, Malayan, or American races.