Soon after, he was invited by the Minister of Agriculture to be the associate director of the section of anthropology, zoology and paleontology of the recently created National Museum of Natural History of Rio de Janeiro, by Emperor D. Pedro II.

The medical anthropologist João Baptista de Lacerda was one of the main exponents of the "thesis of racial whitening" among Brazilians, having participated, in 1911, in the Universal Congress of Races, in London.

Baptista took to the event the article Sur les métis au Brésil (About the mestizos of Brazil, in Portuguese), in which he defended the miscegenation factor as something positive, in the Brazilian case, due to the overlapping of the white race traits on the others, black and indigenous.

The intellectual currents that influenced the thinking of Baptista and other advocates of eugenics were varied and ranged from the determinism of Henry Thomas Buckle and the Social Darwinism of Spencer to the theories of Gobineau.

A curious fact of Baptista's presentation at the Universal Congress of Races was the exhibition of a copy of the painting Ham's Redemption, by the Spanish painter Modesto Brocos.