El nacionalismo visto por la psicología evolutiva
Genetic Similarity Theory extends Anthony D. Smith’s theory of ethno-symbolism by anchoring ethnic nepotism in the evolutionary psychology of altruism. Altruism toward kin and similar others evolved in order to help replicate shared genes. Since ethnic groups are repositories of shared genes, xenophobia is the ‘dark side’ of human altruism. A review of the literature demonstrates the pull of genetic similarity in dyads such as marriage partners and friendships, and even large groups, both national and international. The evidence that genes incline people to prefer others who are genetically similar to themselves comes from studies of social assortment, differential heritabilities, the comparison of identical and fraternal twins, blood tests, and family bereavements. DNA sequencing studies conﬁrm some origin myths and disconﬁrm others; they also show that in comparison to the total genetic variance around the world, random co-ethnics are related to each other on the order of ﬁrst cousins.
Es decir, que la inclinación a mostrar preferencia por nuestros "co-étnicos" (whatever that means) es perfectamente natural. Otra cosa es la exacerbación de ese sentimiento. Como dice Rushton:
The hypothesis presented here is that because 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.
Sobre el "etno-simbolismo", puede verse esta introducción. Sobre la "Teoría de la Similitud Genética", este sintético wiki o, para nota, este artículo del propio Rushton. Una crítica a esta teoría, aqui.