Help please That differences in the shape of heads that could be observed between black Africans & white Europeans, were indication of a moral & rational superiority that justified the slave trade. This is simply racism ladled on top of bad science, but such ideas shaped the immigration policies of the United States and fuelled the ideologies of British imperialists and, later on, the Nazis." ) --> Do further research on scientific racism in the 19th century to explain the reason for these two sentences.