Final answer:
The incest taboo is a cultural universal that exists in every society, prohibiting sexual relations between parents and their offspring and potentially extending to other close relations. The taboo is based on the separation of individuals into two categories: family ties and potential sexual partners.
Step-by-step explanation:
The incest taboo is a cultural universal, which means it exists in every society, although the specific relatives deemed unacceptable for sexual relationships can vary from culture to culture. The taboo prohibits sexual relations between parents and their offspring and sometimes extends to other close relations. For example, in some societies, first cousins are included in the taboo. The incest taboo is based on the recognition of the need to separate individuals into two categories: those with whom they have family ties and those with whom they can establish sexual relationships and other ties.