The relationship between race and migration flows was a central theme in Brazilian social and political thought in the First Republic (1889-1930) (SKIDMORE, 1976; VENTURA, 1991; SCHWARCZ, 1993). As a tropical country that had received thousands of black slaves, Brazil was condemned to decay by the geographical and biological determinisms of the science practiced at that time in Europe. The writer Lima Barreto (1881-1922), posthumously considered one of the nation´s most important authors, attempted to articulate one answer to the scientific racism in his novels, tales and chronicles. Based on the counter-discourse of Jean Finot, Quatrefage, Célestin Bouglé, Kropotkin, among others, Barreto asserted that races don´t exist, denying the biological hierarchy established by authors like Ernst Haeckel, often mentioned in his writings. As a mulatto, Barreto disclaimed the idea that the interracial mixing would lead to degeneration and obstruct the development of a civilization. Instead he suggested that this mixing would be sociologically necessary in a country like Brazil. The writer rejected the ideal of “whitening” adopted by the migration policy of the Brazilian government, according to which migrations flows from Europe would lead to the whitening of mestizos and the extinction of the “black race” (LACERDA, 1911). In contrast to the dominant opinion among Brazilian intellectuals, Barreto didn´t establish conditions for the admission of migrants. In his words, Brazil would be of everybody: “Germans, blacks, caboclos, Italians, Portuguese, Greeks” (BARRETO, 1919). Expressing these ideas through fiction and non-fiction, Lima Barreto was an exception in a debate marked by pseudo-scientific racism, nationalism and restriction to migrations flows. His efforts to deny the process of production of scientific knowledge resemble what is nowadays called postcolonial studies.