Dos Santos and Joaquim Barbosa Gomes, a constitutional law professor and lecturer at Columbia University, say racism is more easily detected in the United States than Brazil and is thus harder to combat. Affirmative action's advocates chide dos Santos Silva and other cautious Afro Brazilians, noting that blacks have been "feeling different" since an estimated 3.6 million slaves toiled throughout the country from 1532 to 1850. That estimate does not include the captured Africans who did not survive the brutal journey to Brazil by ship.