Kinship is the organizing principle of small human societies, such as bands of hunter-gatherers or small farming villages. This is seen in their notions of right and wrong—the same behavior may be wrong toward kin but right toward non-kin, or at least not punishable. Morality is enforced by social pressure from fellow kinfolk, which in extreme cases can lead to ostracism and banishment.

This kin-based morality breaks down as societies grow larger and as the circle of regular interaction spreads beyond close kin. Wrongdoers are less easily brought into line because they and their victims no longer share the same kinfolk. Wrongs have to be avenged through vendettas: my clan against yours. Since vendettas can go on indefinitely, causing much more harm than the initial wrongdoing, a society cannot be both large and orderly unless it can resolve disputes between unrelated individuals. Hence, the development of codified law and justice systems. Hence the prohibition of violence as a means to resolve personal disputes.

In much of the world, this is as far as cultural evolution has gone. The circle of trusting relationships extends no farther than one’s kinship ties; beyond, morality is enforced only by the force of law, and court justice is expensive, time-consuming, and not always impartial. So dealings with non-kin are kept to the minimum necessary. This low level of trust restricts trade, keeping it bottled up spatially and temporally in marketplaces and family businesses. A true market economy cannot self-generate.

Cultural evolution has gone farther in two parts of the world: Northwest Europe and East Asia. The outcomes are rather similar—peaceful, orderly societies encompassing large numbers of people—but they have come about differently. Northwest Europeans could pursue this trajectory because they already had relatively weak kinship when they began to develop larger and more complex societies in the 12th century. There was a pre-existing tendency to live outside kinship structures, as seen in the Western European Marriage Pattern: men and women married relatively late and many never married; children usually left the family household to form new households; and many individuals circulated among non-related households, typically young people sent out as servants (Hajnal, 1965; Hallam, 1985; Hartman, 2004; Seccombe, 1992). This weak kinship environment was made possible by three mental adaptations: greater capacity for involuntary guilt and empathy; greater receptiveness to absolute moral norms, as opposed to relativistic ones based on kinship; and stronger desire to punish, exclude, and even kill violators of these norms (Frost, 2014a; Frost, 2014b).

When the Dark Ages came to an end, Northwest Europeans were well positioned to exploit the possibility of creating a larger and more complex social environment. Their mental makeup “pre-adapted” them for a trajectory of increasingly radical change: strengthening of Church and State, expansion of Christian guilt culture, pacification of social relations, and reorganization of these relations independently of kinship to create new forms of social organization (market economy, nation state, ideological regime, etc.).

East Asians have followed a different trajectory to a similar end, relying less on internal means of behavior control (guilt, empathy) and more on external means (shaming, family discipline, community surveillance, notions of moral duty). The main difference is in the relationship between self and society. Whereas a greater sense of self has helped Northwest Europeans to transcend the limitations of kinship and, thus, build larger societies, East Asians have relied on a lesser sense of self to create a web of interdependence that extends beyond close kin. There is a stronger tendency toward holistic attention, emphasis on social (versus personal) happiness, and suspension of self-interest. Conversely, there is a weaker tendency toward self-expression, self-esteem, and self-efficacy (Kitayama et al., 2014).

This trajectory may have been particularly favored by rice farming, which requires community planning of water use and community construction of irrigation networks. Even when neighboring districts are compared in China, individualism seems to be much weaker where rice is grown than where wheat is grown. This pattern holds up even in urban residents who have never actually lived on a farm and whose connection to rice farming is only genealogical (Talhelm et al., 2014).

Gene-culture co-evolution

Our biological selves have evolved to meet not only the demands of our natural environment but also those of our cultural environment. There has thus been selection for certain aptitudes, predispositions, and personality types.

For instance, if a culture favors individuals who respond more readily to the problems of others, this response will become more common with each passing generation, since affective empathy has a heritability of 68% (Chakrabarti et al., 2013). There is no need to create this mental trait from scratch. Affective empathy exists to varying extents in all humans, although it is stronger in women, perhaps because it originally served to strengthen the caring relationship between a mother and her children (Baron-Cohen and Wheelwright, 2004; Frost, 2014a). In Northwest Europeans, it has become more generalized, being felt by all normal individuals toward all people, except for those who are judged to be morally worthless. The result is a higher level of interpersonal trust and the development of social relations that would otherwise be impossible (Medrano, 2010).

Are there biological markers of this gene-culture co-evolution in Northwest Europeans? Enlargement of the amygdala is known to be associated with high altruism toward strangers, and two studies, one in southern California and the other in London, have found a larger amygdala in “conservatives” than in “liberals” (Kanai et al., 2011; Marsh et al., 2014; Schreiber et al., 2013). The difference may actually be an ethnic one, given the voting patterns in both areas.

In East Asians, pro-social behavior is supported not so much by empathy as by notions of duty toward the community (Frost, 2014b). This trajectory of gene-culture co-evolution seems to have its own biological markers, notably certain changes to the dopamine signaling system. In a recent study, a sample of Euro-Americans was compared with a sample of East Asians born in China, Korea, or Japan. The participants were genotyped for the dopamine D4 receptor gene (DRD4) and then administered a test on their social orientation. The test showed that the East Asians were less individualistic than the Euro-Americans, but this psychological difference was limited to carriers of DRD4 variants that increase dopamine signalling, i.e., 7- or 2-repeat alleles. Non-carrier East Asians were just as individualistic as non-carrier Euro-Americans (Kitayama et al., 2014). It seems that the East Asian cultural environment can reduce individualism only among individuals who carry these variants.

This finding is puzzling in one sense. Previous work has shown that the same DRD4 variants are associated with risk seeking and heavy drinking. The authors suggest that these variants make people more willing to imitate their peers, be they drinking buddies or ma and pa:

It might be the case that the 7R and 2R alleles are associated with greater acquisition of culturally sanctioned social orientations under generally favorable conditions of socialization, such as careful guidance and scaffolding of norm-congruous behaviors by socialization agents (e.g., parents, relatives, neighbors), but with markedly different, deviant behaviors (e.g., delinquency and risk proneness) under unfavorable social conditions or adversity, which might “reward” externalization or risk taking. (Kitayama et al., 2014)

Although one gene may largely explain why East Asians differ from Euro-Americans in social orientation, other genes may be involved in this and other differences between the two groups:

The current work has some bearing on the coevolution of cultural systems and genetic polymorphisms. Chiao and Blizinsky (2010) suggested that certain alleles of the 5-HTTLPR polymorphism of the serotonin transporter gene might have coevolved with cultural collectivism and individualism. They argued that although a short allele of 5-HTTLPR is linked to anxiety and depression, especially under traumatic life conditions (Caspi et al., 2003), this genetic risk might be mitigated by cultural collectivism, which involves more caring social relations and support networks. Cultural collectivism might therefore “buffer genetically susceptible populations from increased prevalence of affective disorders” (p. 529), which in turn might lead to a relatively high prevalence of the short allele of 5-HTTLPR. (Kitayama et al., 2014)