competition between ethnic groups provides selective pressure for cooperation(social classes, social structures, ethno-centric religion, empathy, morals ect). once one group has won and consolidated power the selective pressure is reduced greatly leading to the formation of social cancer. social parasites can also be considered as being able to exist in consolidated systems. imagine a germany infected by social parasites and greatly weakened vs an ethno-centric france. this is naturally resolved by balkanisation and a warring states period with hundreds or thousands of different tribes that have different behavioural traits/religions/moral frameworks ect. the best rises to the top and consolidates power.
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