Samuel Morton's name is well-known in anthropology, but the fact that he is well-known does not necessarily mean that he is well-respected. Morton's anthropological theories were well-accepted in his day, largely because they seemed to confirm pre-existing beliefs about racial inequality. However, his theories have not held up to scientific scrutiny. On the contrary, many modern scientists believe that Morton and similarly-situated scientists allowed personal bias to influence their scientific findings to a very strong degree, so that they could use exaggerated racial differences to justify the different treatment that people received because of their races.

Because of the impact that Morton's work had on race relations, it is important to consider when Morton was working when reviewing his work. Morton lived and worked in the antebellum United States, when slavery was still a legal institution and when even non-slave states proscribed very different treatment for people because of their race. Morton did not begin his studies by concentrating on race. On the contrary, he went to the University of Pennsylvania and Edinburgh University in Scotland, where he studied medicine and natural science. He practiced as a doctor in Philadelphia, and then became a professor of anatomy at the University of Pennsylvania. During his time as a doctor, he began studies that combined a mixture of what is modernly-known as paleontology and some anthropology. He also wrote medical papers.

However, Morton is not famous for his natural science essays or for his medical research. Instead, he is famous for the dubious role that he played in originating "American School" ethnography. While researchers in many locations noticed obvious physical differences between the races, the "American School" was notable because its adherents proclaimed that the different races were actually different species. While Morton's work may not have been written with the intention of promoting slavery, it was certainly used by pro-slavery forces as a means to do so. After all, if African-Americans were actually members of a distinct species, then ownership of them would become a much less problematic moral issue. Not that Morton's work singled-out African-Americans as the only people who were racially inferior to Europeans. On the contrary, Morton considered all non-Caucasians to be inferior to Caucasians.

Morton was fascinated by the human skull, and literally collected skulls from all over the world. In fact, "between 1820 and his death in 1851, Morton collected over 1,000 human skulls." (Facing History and Ourselves). He started with the basic premise that intellectual abilities could be judged by skull size. This premise is not without precedent. For example, human beings are considered the most intelligent of animals and do have skulls that are disproportionately large in comparison to their bodies, when compared to other mammals. Furthermore, less intelligent animals do tend to have smaller brains, though the correlation between skull size and brain size is not direct. However, science had yet to make those discoveries, and Morton proposed that he could predict intelligence from skull size.

Morton measured the skulls to give him an approximation of brain size. What he concluded was that whites have larger skulls than members of other races, which made them intellectually superior. While Morton is seen as an originator of the "American School," he actually was not certain whether the races were separate species. However, Morton was adamant that blacks were different from, and inherently inferior to, whites. In fact, though Morton initially resisted the idea of polygenesis because it conflicted with the origination story in the Bible, but eventually began to suggest that the races of the world did not share a common origin. In this way, he opened the door to the belief that the different races were actually different species.

Morton divided humans into four primary races, though he acknowledged differences between members of the same race. Those races were Caucasians, Mongolians, Americans, and Africans. He used the term Caucasian to refer to people of European origin, the term Mongolian to refer to people of Asian origin, Americans to refer to Native Americans, and Africans to refer to people of African origin. While Morton's scientific efforts theoretically concentrated on skull size, reading his works, one sees an emphasis on characteristics that have nothing to do with skull size.

Morton notes that Caucasians are characterized by fair skin, fine long and curling hair, small oval faces, and well proportioned features.…