On the Evolution of Social Organization

Any sort of social organization involves at least two individuals of the same species. If this behavioral interaction becomes regular and predictable, we have a dyadic social relationship, the simplest form of social organization. The number of dyadic relationships in a group is given by the formula n(n-1)/2, where n is the total number of individuals in the group. That is, each time a new individual is added to a group, the number of dyadic relationships is increased by a figure equal to the number of individuals previously in the group.