The theory views ethnocentrism and racism as nepotism toward extended kin and an extension of kin selection. In other words, ethnic nepotism points toward a biological basis for the phenomenon of people preferring others of the same ethnicity or race; it explains the tendency of humans to favor members of their own racial group by postulating that all animals evolve toward being more altruistic toward kin in order to propagate more copies of their common genes. "The myth of common descent", proposed by many social scientists as a prominent ethnic marker, is in his view often not a myth at all. "Ethnicity is defined by common descent and maintained by endogamy". To guard one's genetic interests, Frank Salter notes altruism toward one's co-ethnics: Regarding how this translates into politics and why homogeneous societies are more altruistic, Frank Salter writes: J. Philippe Rushton has complemented kin selection and ethnic nepotism by his genetic similarity theory which proposes that "genetically similar people tend to seek one another out and to provide mutually supportive environments such as marriage, friendship, and social groups. This may represent a biological factor underlying ethnocentrism and group selection". He has also argued that:
ecause fellow ethnics carry copies of the same genes, ethnic consciousness is rooted in the biology of altruism and mutual reciprocity. Thus ethnic nationalism, xenophobia and genocide can become the ‘dark side’ of altruism. Moreover, shared genes can govern the degree to which an ideology is adopted. Some genes will replicate better in some cultures than in others. Religious, political and class conflicts become heated because they affect genetic fitness. Karl Marx did not take his analysis far enough: ideology may be the servant of economic interest, but genes influence both. Since individuals have a greater concentration of genetic interest in their own ethnic group than they do in other ethnic groups, they can be expected to adopt ideas that promote their group over others. Political ethologist Frank Salter refers to ideologies as ‘fitness portfolios’, and psychologist Kevin MacDonald has described co-ethnics as engaging in "group evolutionary strategies."
In Rushton's interpretation it is not clear whether the proposed genetic likeness that supports ethnic nepotism is limited to external appearance, or it also includes other loci. If that is the case, it would be difficult to deduct how similar blood types or creatine levels, or others, among the multitude of invisible phenotype traits, contribute to determine the bonding behavior towards people carrying the alleged similar alleles. Also, there is no clue offered as to which of these specific alleles are the most important for expression of ethnic nepotism. Hamiltonian kin selection refers exclusively to defined sets of discrete behaviors that are innate, not learned and increase the reproductive fitness among very close kin, whereas ethnic nepotism would appear to depend heavily on social interactions and on morphology, or physical characteristics. According to research by Van der Dennen, "ethnocentrism-cum-xenophobia" seems universally present in preindustrial societies. Tatu Vanhanen in his 1999 book Ethnic Conflicts Explained by Ethnic Nepotism empirically examined the relationships between the degree of ethnic homogeneity, the degree of ethnic conflicts, and the degree of democratization in the nations of the world. He found that more ethnically heterogeneous nations had more ethnic conflicts. The degree of democratization explained very little of the degree of ethnic conflicts except that very authoritarian states such as the former Soviet Union and Yugoslavia could suppress ethnic conflicts. Ethnic conflicts were only slightly less common in more economically developed countries. They appeared within all racial groups, cultures, and geographical regions. In Vanhanen's view, people have a genetic tendency to easily learn ethnic attitudes and psychological mechanisms leading to prejudice, scapegoating, and discrimination.
