It's not "ethical monotheism" propping up civilization as can be seen by the "Florida effect" where people are far more likely to agree to being taxed to support local schools that share the same genes as them, while they resist being taxed to support what they consider foreign invader gene pools.  It's simply the fact that they view people with the same genes as them as being possible relatives and treat them as such (a selfish gene type scenario) instead of killing or stealing from them.