"Natural" is an understatement or perhaps wrong category. Our all cognitive processes necessarily involve hierarchies - without hierarchies we could not differentiate, categorize, arrange, analyze, organize - in a word, think in rational terms. Things have no meaning if they are not placed in a context that by very definition involves some form of hierarchical arrangement.
It is only natural that hierarchy defines human relations, especially those involving specialized roles and a large number of individuals. Trying to get rid of hierarchies is sheer lunacy. The point is not to eliminate them, but to reduce some of their dysfunctional qualities.