In 2010, Henrich, Heine, and Norenzayan reported a systemic bias in conducting psychology studies with participants from "WEIRD" (western, educated, industrialized, rich and democratic) societies. Although only 1/8 people worldwide live in regions that fall into the WEIRD classification, the researchers claimed that 60–90% of psychology studies are performed on participants from these areas.In particular, the American nuclear family is considered weird to most of the world, and to most non-Whites and non-Christians.
Here is what underlies the differences:
Henrich does not express himself in these blunt terms, but for the sake of immediate clarity, his basic argument about WEIRD people is that they see themselves as individuals rather than as members of collective ingroups. Their individualism is the difference that underlies all the other differences. It is the difference that explains why WEIRD people are less attached to extended families, tribal units, religious groups and even nation states. Because WEIRD people judge others as individuals, they are willing to extend their trust to outsiders, to people from other ethnic backgrounds and nationalities. They are more inclined to be fair to outsiders, judging them on the basis of impersonal standards rather than standards that only serve the interests of their ingroup. WEIRD people are less conformist, more reliant on their own individual judgments and capacities, willing to reason about issues without following the prescribed norms and answers mandated from collective authorities. In the non-Western world, trust is circumscribed within one's ingroup rather than extended to individuals from outgroups.The article traces these difference further back, to the Ice Age and development of agriculture:
The key to the individualism of WEIRD people is their lack of kinship ties. The most important norms and institutions humans have developed to regulate their social behavior revolve around kin groups, which are networks of individuals connected by blood ties, extended families and clans. Humans are born into these kin groups; their survival, identity, status and obligations within society, as well as their sense of right and wrong, who and when they should marry, where they should live, who owns the land and how property should be inherited, are determined by the norms of the kin group.
Given the importance of kinship networks in determining whether people are "normal" or WEIRD, Henrich set out to find what factors may have led to the breakdown of kinship networks in the West. His conclusion was that the Catholic Church was responsible for the "demolition" of kinship networks and the rise of WEIRD people.
MacDonald observes that, as members of the same Homo sapiens species, all humans have common biological adaptations, but they do "differ in degree in adaptations" depending on environments, and these differences can generate "major differences" between cultures. Under the "harsh evolutionary pressures of the Ice Age," there would have been more pressures to live in small groups and in relative social isolation, rather than to form "extended kinship networks and collectivist groups" competing in close proximity for resources. There were selective pressures for males to provision simple households or nuclear families characterized by monogamy, exogamy, and bilateral kinship, because the ecology and availability of resources could not have selected for large polygynous families. This was in contrast to Near Eastern regions with their long fertile rivers supporting "large tribal groups based on extended kinship relations". The strategy pursuit by northern Europeans was quite successful, enabling them to develop complex hunting gathering cultures during the Mesolithic era for a long time, 15,000 to 5,000, delaying the advance of farming which was slowly spreading into central and north Europe after Anatolian farmers settled in various parts of southern Europe starting 8000ybp.This analysis doesn't explain how much is nature, and how much is nuture. Presumably some of these difference are innate. But whether they are or not, they appear to have persisted for millennia, and are unlikely to change anytime soon.
Mesolithic cultures in Europe did consist of larger bands of hunter-gatherers due to their more efficient exploitation of resources and improved stone age tools, but lacking any "stable resource" that could be controlled by an extended lineage group, their residences remained seasonally occupied by relatively small families living in a state of egalitarian monogamy and without one extended family superimposing itself over the others by controlling fertile and stable land areas. In northern Europe, families "were periodically forced to split up into smaller, more family-based groups". These smaller groups were forced to interact both with related families and with "non-kin and strangers" also moving around from season to season. These interactions were not regulated by kinship norms but instead led to emphasis on "trust and maintaining a good reputation within the larger non-kinship based group".
These evolutionary selected behaviors characterized by small families, exogamous and monogamous marriages, and relations based on trust with outsiders, were the primordial ground out of which Western individualism emerged.
In the Near East complex hunting gathering societies soon evolved into agrarian villages controlled by lineage groups in charge of stable resources. I would add, as Jared Diamond observed, that most of the animals and plants susceptible to domestication were found in the Near East, which encouraged or made it easier to develop farming villages with plentiful resources controlled by the stronger kinship groups. Whereas monogamy and exogamy persisted in the West, in the East the tendency was for marrying relatives, even first cousins.
The European practice of marrying outside the extended family meant that marriage was more likely "based on personal attraction", which meant that there was selection for physical attractiveness, strength, health and personality, in contrast to the East where marriage was arranged within the extended family. Love and intimacy between wife and husband, including greater affection and nurturance of children, MacDonald observes, were a salient trait of Europeans. Whites invented romance, in contrast, for example, to Semitic marriages where marriages were intended to solidify kinship ties, arranged by elders, with love and romance having a far lesser role.