The evolution of complex societies can be attributed to several factors. The prevalent theory which explains the start of complex societies is the pressure exuded by warfare or a method to organize a population of approximately more than 150. Warfare contribution to establishing complex societies by creating pressure for comprehension between groups which strengthens the cooperation in groups, it improves the organization of the groups structure , and pushes the desire to grow the population of the group. The growth of population results in the loss of person to person interaction which creates a need for a system to keep track the interaction between the leads of the group. The groups would then create symbols of either language, clothing or ideology to identify who belongs to the group and where are their position in the society. The process of identifying the who resides in the groups also expands to identifying the power structure of the group. The identification of the power structure within the group is commonly distributed as a hierarchical power structure meaning groups are organized with one head of the group overseeing the whole group. The group will eventually grow to a state in which labor is divided within specializations meaning that there are branches in the society that are in charge in military affairs, laws, or religion of said society, the elites of the society occupied the leading positions in the branches.