Introduction

The difference between a living and a dead social system—of whatever size, be it the largest or the smallest—is the presence, or the disappearance (due to death or migration), of its members.

A social system lives through its membership. Individuals who belong to it may die or withdraw; their replacement is a must if a system is to survive. Since a social system is a plurality of interacting individuals, the first functional prerequisite is the presence of individuals-in-interaction. Since individuals have a limited life span compared to a social system—particularly a society or a community—the system must ensure their replacement when they die or move out.

Every social system has to attend to the question of recruitment of its membership, of ensuring continuing membership. For societies as a whole, this recruitment prerequisite is fulfilled through the institution of marriage—persons of opposite genders are united for the purpose of sexual congress, necessary for the process of reproduction. The continual living together of mating partners and their progeny creates conditions for the small primary group called the Family.