Except for signifying potential group danger, primate signals rarely apply to events outside the group, such as the presence of food or water. They are totally within group affairs and are not evolved to give environmental information in the way human languages are. Now this is what we start with. Within a specific ecology, for most species, it is this communication system that limits the size of the group. Baboons are able to achieve groups as high as eighty or more because they have a strict geographical structure as they move about on the open plains, with dominant hierarchies being maintained within each circle of the group. But in general the usual primate group does not exceed thirty or forty, a limit determined by the communication necessary for the dominance hierarchy to work. In gorillas, for example, the dominant male, usually the largest silver-backed male, together with all the females and young, occupies the central core of each group of about twenty, the other males tending to be peripheral. The diameter of a group at any given moment rarely exceeds 200 feet, as every animal remains attentive to the movements of others in the dense forest environment. The group moves when the dominant male stands motionless with his legs spread and faces a certain direction. The other members of the group then crowd around him, and the troop moves off on its leisurely day’s journey of about a third of a mile. The important thing here is that the complex channels of communication are open between the top of the dominance hierarchy and all the rest. There is no reason to think that early man from the beginning of the genus Homo two million years ago lived any differently.

• reason
• work
• structure
• communication
• danger
• behavior
• dominance
• environment
• food
• hierarchy