I know that in some social animals there is a hierarchy that does get established but what about with humans? How do we explain those who developed hierarchies and those who didn’t?
I think hierarchies are important for many animals because it maintains group uniformity, especially for social animals such as human beings. If everyone was challenging everyone else in a social group it would not be long before it began to disintegrate. With a hierarchy established members know whereabouts on the ‘pecking order’ they are and this maintains a relative degree of stability for the group. In our hunter-gatherer past it would have been essential for small human groups to co-operate with one another in the interests of survival and without some kind of leadership established the group would not have been very coherent and effective. This is reflected nowadays in every walk of life where a system of ‘management’ has to be in place in order to make some enterprise to function effectively.