The purpose of this article has been to explore why ethnic conflicts tend to break out in all ethnically divided societies. The principal explanation was traced to the evolved disposition for ethnic nepotism shared by all human populations. Ethnic nepotism was measured roughly by the degree of ethnic heterogeneity of the populations. It was correlated with the scale of ethnic conflicts in the group of 187 countries. The results of correlation analysis indicate that ethnic heterogeneity explains 55% of the variation in the scale of ethnic conflicts, and the results of regression analysis disclose that the same relationship more or less applies to all 187 countries. These results led to the conclusion that ethnic nepotism is the common cross-cultural background factor which supports the persistence of ethnic conflicts in the world as long as there are ethnically divided societies.
I tested this hypothesis by empirical evidence on the level of ethnic conflicts and the degree of ethnic heterogeneity, and checked the results by some alternative explanatory variables. The results of correlation analyses indicate that ethnic heterogeneity of the population (EH) explains 55% of the variation in the five-level scale of ethnic conflicts (EES), whereas the best alternative explanatory variable (HDI-12) does not explain more than 28% of the variation in EES. The results of multi-regression analysis, in which all five alternative explanatory variables (national IQ, HDI-12, Economic Freedom, ID-12, and GNI per capita income) together with the degree of ethnic heterogeneity are used to explain the variation in EES, show that the explained part of variation in EES rises from 55% to 60%. It is only 5 percentage points more than what EH alone explains.
I came to the conclusion that the degree of ethnic heterogeneity is by far the most important explanatory variable. Only 45 percents of the variation in EES remained unexplained. The unexplained variation is probably due to measurement errors, accidental factors, and various unknown cultural and environmental factors. Because many different and unrecognized factors affect the scale values of EES, it would be unrealistic to hope that any explanatory variable could explain all or nearly all of the variation in EES. The achieved explanation of 55% is already extremely high. The impact of ethnic nepotism explains why the scale of ethnic conflicts in