Family wars

Family feuds can be terrible, and divorce is the worst. That may be because people who trusted each other find themselves victims of treason, and react violently. Does this scale up to relationships between nations?

Enrico Spolaore and Romain Wacziarg find that populations that are genetically closer tend to be more frequently at war, after obviously controlling for geographic distance. They favor the explanation that sharing genes means also sharing preferences over scarce goods. I prefer the family trust story. Seeing how vicious civil wars are does not discredit either theory as well.