Tiedemann was one of the first persons to scientifically contest racism. In his article entitled "On the Brain of the Negro, compared with that of the European and the Orang-outang" (1836), he argued based on craniometric and brain measures taken by him from Europeans and black men from different parts of the world that the then-common European belief that Negroes have smaller brains and are thus intellectually inferior is scientifically unfounded and based merely on the prejudice of travellers and explorers.