Social and natural sciences, from the beginning, studied different human populations and their biological and behavioral similarities and differences. From the middle of the 18th century two diverse approaches arose, one saw all humans as members of one single biological species and this approach is known as monogenetic; while the other approach viewed human populations as distinct biological species and this approach is known as polygenetic. Famous Swedish biologist and taxonomist Carl Linnaeus, in the tenth edition of his book Systema Naturae (1758) stated that all humans are members of a single human species, which put him in a monogenetic camp. He did not use the term “race”, but used the term “varieties”. According to him, there are four varieties of humans divided by their continent and skin color: European (white), African (black), Asian (yellow), and American (red).

English philosopher David Hume, in the essay Of National Characters (1754), similarly posits that differences between European nations are the result of cultural and political influences and are not a consequence of natural differences. Concerning other human populations Hume writes: “I am apt to suspect the negroes and in general all the other species of men (for there are four or five different kinds) to be naturally inferior to whites. There never was a civilized nation of any other complexion than white, nor even any individual eminent either in action or speculation”. German philosopher Immanuel Kant, in his essay Of the Different Human Races (1775) purported that all human populations are from the same line originating from Europe. Migrations, geographic isolation, and ingroup breeding all produced four distinct and pure races: noble blond (Europe), copper red (America and east Asia), black (Africa), and olive-yellow (Asia-India).

German author Johann Friedrich Blumenbach (1752–1840), who is considered the father of modern anthropology, introduced his typology of human varieties or races – Europeans (Caucasians), Asians (Mongolians), Africans (Ethiopians), Americans, and South Pacific islanders (Malayans). He was the first to coin the term “Caucasian” to denote people of Europe, West Asia, and Nothern India. Hume, Kant, and Blumbenbach believed in the monogenetic origin of human races and that they all represent one biological species.

Some of the strongest proponents of polygenesis were American authors Charles Cadwell, and Charles Pickering, and members of the “American School of Anthropology,” represented by authors like Louis Agassiz, Robins Gliddon, and Josiah Clark Nott. In Europe, strong and influential supporters of the polygenesis hypothesis were French naturalist Georges Cuvier, Swedish anatomist Anders Retzius, and British anatomist Robert Knox.

One of the most influential racial theorists was French author Arthur de Gobineau (1816–1882). Although he changed his position, throughout his life, on the issue of the monogenetic and polygenetic origin of human races, he always supported the idea of white racial supremacy. Gobineau stated that there are three original and distinct human races: white, black, and yellow, with the white race being at the top of the hierarchy. He saw Germans as the best representatives of the Arian race and biological and cultural descendants of the Romans. In the book, Inequality of the Human Races (in French 1853–1855) Gobineau stated that there are two human impulses, one of attraction and one of repulsion. Civilizations are the product of following the law of attraction, the case in which members of different races mix. White races are the product of racial intermixing, while other races followed the low of repulsion. Once civilization is achieved intermixing of races turns into degeneration. Prevention of race mixing and segregation is natural and represent the  “spirit of isolation”. The white race, according to Gobineau, should dominate over other races and will continue to be successful in that goal, as long as it keeps its racial purity. when a stronger race achieves domination over their newly conquered land the “principle of death” emerges.

British political philosopher Houston Chamberlain (1855–1927) was a follower of Gobineau’s ideas of a German master race, predicting the growth of the “Aryan” strength, and supporting racial policies. British biologist Francis Galton (1822–1911) introduced the term “eugenics”. Eugenics was supposed to be a method of keeping racial purity, mostly focusing on physical attributes like health, manliness, and courteous disposition. Positive eugenics would entail forced and restricted breeding of members of the higher races, while negative eugenics, which was implemented in some countries, involved the sterilization of people with physical or mental disabilities. Galton also believed that Europeans were more intelligent than “primitive races” and supported the quantification of levels of racial intelligence. Most of the proponents of social Darwinism were also supporters of racial theories.

Pioneer of social psychology Gustave Le Bon (1841–1931) viewed different races as physiologically and psychologically distinct groups imbued with unchanging race souls. In American psychology, many authors conducted race psychological studies that measured differences in intelligence between different races. The results of those studies showed innate cognitive differences between members of different races.

Some of the notable examples of racist approach in American psychology are: Granville Stanley Hall, Robert M. Yerkes, and Lewis Terman. The height of the racist approach in American psychology was at the beginning of the 20th century, and after WW II, it lost its relevance. The new impetus for the revival of racism in American psychology was the article "How Much Can We Boost IQ and Scholastic Achievement?" written by Arthur Jensen. He concluded that educational programs like Head Start, which were created with the goal of improving the educational achievements of racial minorities, had failed. He stated that the reason for this failure is innate genetic factors and he estimated that  80% of the variance in IQ in the population studied was due to genetic differences.

Similar claims appeared in the notorious book The Bell Curve (1994) by Richard Herrnstein and Charles Murray. Canadian psychologist Philippe Rushton promoted ideas of racial hierarchy and innate differences in intelligence between races. His evolutionary explanation for those differences was based on behavioral differences caused by climatic and economic factors that existed in Europe and Asia, which favored larger brains when compared to those factors that were present in Africa. One of the latest examples of racist theories in social sciences is the book Race and Evolution: The Causes and Consequences of Race Differences (2022) by American sociologist Stephen Sounders.