The Kingdom of Serbs, Croats and Slovenes was founded in December 1918 upon the notions of ethnic-racial homogeneity derived from nineteenth century Romanticism. A wide gulf soon arose between Croats and Serbs, since the new South Slav state bore an undeniably dominant Serbian political and cultural stamp. Yugoslavia became a state in which a 'core' or 'dominant' ethnie, in other words the Serbs, governed over the other 'peripheral' ethnies, namely the Croats. Cvijic promoted the idea of the common Dinaric racial identity of the Yugoslavs. In Croatia, the theory of the core Nordic-Dinaric racial identity of the Yugoslavs was mainly promoted by the Croat-Slovenian biologist Boris Zarnik, a professor of biology at the Faculty of Medicine in Zagreb. Zarnik addressed the important racial-theoretical question as to whether the Nordic race was the only truly creative race.Keywords: Boris Zarnik; core Nordic-Dinaric racial identity; Croats; ethnic-racial homogeneity; nineteenth century Romanticism; Serbs; Slovenes; Yugoslavia