Mapping the end of incest and dawn of individualism

Mapping the end of incest and dawn of individualism, by Caitlin McDermott-Murphy.

If you’re from a Western society, chances are you value individuality, independence, analytical thinking, and an openness to strangers and new ideas.

And the surprising reason for all that may very well have to do with the early Roman Catholic Church and its campaign against marriage within families, according to new research published in Science by Joseph Henrich, chair of the Department of Human Evolutionary Biology, and a team of collaborators. …

About a decade ago Henrich coined the acronym WEIRD (Western, educated, industrialized, rich and democratic) to describe the characteristics of cultures that embrace individualism. And those groups were weird, which is to say unusual within the rest of the modern world’s substantial psychological variation. …

“There’s good evidence that Europe’s kinship structure was not much different from the rest of the world,” said Jonathan Schulz, an assistant professor of economics at George Mason University and another author of the paper. But then, from [around 600 AD] to 1500 A.D., the Western Church (later known as the Roman Catholic Church) started banning marriages to cousins, step-relatives, in-laws, and even spiritual-kin, better known as godparents. …

Comparing exposure to the Western Church with their “kinship intensity index,” which includes data on cousin marriage rates, polygyny (where a man takes multiple wives), co-residence of extended families, and other historical anthropological measures, the team identified a direct connection between the religious ban and the growth of independent, monogamous marriages among nonrelatives. According to the study, each additional 500 years under the Western Church is associated with a 91 percent further reduction in marriage rates between cousins.

“Meanwhile in Iran, in Persia, Zoroastrianism was not only promoting cousin marriage but promoting marriage between siblings,” Henrich said. Although Islam outlawed polygyny extending beyond four wives, and the Eastern Orthodox Church adopted policies against incest, no institution came close to the strict, widespread policies of the Western Church.

Those policies first altered family structures and then the psychologies of members. Henrich and his colleagues think that individuals adapt cognition, emotions, perceptions, thinking styles, and motivations to fit their social networks. Kin-based institutions reward conformity, tradition, nepotism, and obedience to authority, traits that help protect assets — such as farms — from outsiders. But once familial barriers crumble, the team predicted that individualistic traits like independence, creativity, cooperation, and fairness with strangers would increase. …

Although willingness to trust strangers, as opposed to family or neighbors, is associated with higher levels of innovation, greater national wealth, and faster economic growth, which factor causes which is not yet known.