Davis and Moore claim that all societies have some form of social stratification and George Peter Murdock maintains that the family exists in every known human society. From these observations it is assumed that institutional arrangements such as social stratification and the family meet needs which are common to all societies.
Thus from the universal presence of social stratification it is argued that all societies require some mechanism to ensure that social positions are adequately filled by motivated persons. From the universality of the family it is assumed that some mechanism for the reproduction and socialization of new members is a functional prerequisite of society.