This paper discusses the role of hierarchy in human systems. Two kinds of self-organizing processes are distinguished: conservative and dissipative self-organization. The former leads to rather stable, specialistic systems, whereas the latter leads to continuously changing generalistic systems. When conservative and dissipative self-organization are combined, autonomous self-organization emerges. Autonomous self-organization, characterized by intertemporal stability, appears to be fundamental to human organizations. In the context of autonomous self-organization, the traditional concept of hierarchy as a chain of command is replaced by hierarchy as a vertical sequence based on different degrees of abstraction. Moreover, a simple model shows that autonomous self-organization requires large human systems to use a variety of information processing systems, including administrative hierarchy. The model suggests hierarchy is one instrument for variety reduction amid several others.