Complex sentence: It has long been known that a large group or organization of people will begin to behave as a single entity, taking on a consciousness and will of it's own, which may completely contradict the minds and wills of the individual members.
Split into simpler sentences: It has long been known that a large group or organization of people will begin to behave as a single entity, taking on a consciousness and will of its own. This consciousness may completely contradict the minds and wills of the individual members.