Structural universal

A family system is a structural universal - it appears in all known human societies. However, in this example a cultural universal refers to the idea that a particular family type appears in all societies (for example, a family structure consisting of one or more children plus two adults of the opposite sex - the technical term for which is a nuclear family structure).

In this particular instance, it is debatable as to whether or not this type of cultural organisation does, strictly speaking, appear in all known societies. As writers such as Rhona and Robert Rappoport have argued, there is a wide range of cultural variation in family types not just between societies but also within the same society.