Jonathan F. Schulz
Yale University, Department of Psychology, November 29, 2016
Abstract:This paper highlights the role of kin-networks for the functioning of democracy: countries with strong extended families as characterized by a high level of cousin marriages exhibit a weak rule of law and are more likely autocratic. To assess causality, I exploit a quasi-natural experiment. In the early medieval ages the Church started to prohibit kin-marriages. Using the variation in the duration and extent of the Eastern and Western Churches’ bans on consanguineous marriages as instrumental variables, reveals highly significant point estimates of the percentage of cousin marriage on an index of democracy. An additional novel instrument, cousin-terms, strengthens this point: the estimates are very similar and do not rest on the European experience alone. Exploiting within country variation of cousin marriages in Italy, as well as within variation of a ‘societal marriage pressure’ indicator for a larger set of countries support these results. These findings point to a causal effect of marriage patterns on the proper functioning of formal institutions and democracy. The study further suggests that the Churches’ marriage rules – by destroying extended kin-groups – led Europe on its special path of institutional and democratic development. [emphasis added] (Source)
The full paper is available at the link above.
Basically, cousin marriage results in clans which results in clannish societies that do not function well under the democratic and legal institutions of the West.
And this is a major reason multiculturalism is failing in the West. Here is more on this subject: Some very basic anthropology and how that affects news and politics.
Here is a graphic that shows consanguinity (cousin marriage) rates across the globe.