People are on average moved by their own interest. People are not motivated by abstract religious or cultural ideas. Of course there are in all societies and all times idealistic individuals acting upon altruistic or out-of-the-earth motivations, by they always remain a minority. When whole societies are concerned, over the long term, only egoistic motivations play a role. Up to a very good approximation, the resulting evolution of a society is the sum of all egoistic moves by its individuals.