Generally, monotheism is favorable to a high level of organization, including complex theologies that don’t just morph a lot but are only changed with much deliberation or controversy. But did that state of affairs evolve so as to foster “cohesive unity,” as Harari suggests? Hard to say. Religion — especially propositional religion, like the monotheisms — can foster either unity or disunity. Monotheism has not been a force for unity in Northern Ireland or the Middle East.
The oldest type of religion was probably a form of naturalism. Non-naturalist religions are better accounted for by revelation.
The “evolutionary” view (Darwinism, in fact) is often portrayed as a sort of liberation but people may be rather surprised to discover exactly what that liberation is.