Final answer:
The statement that the universal incest taboo includes a prohibition against sexual relations with one's parallel cousin is false, as the taboo varies across cultures and the extension to other family relations like cousins can differ significantly.
Step-by-step explanation:
The statement that the universal incest taboo dictates one does not have sexual relations with one's parallel cousin is False. The universal taboo principally refers to the prohibition of sexual relations between parents and their offspring, and it can vary in its extension to other family relations across different cultures. For example, while in some cultures, sexual relations with a parallel cousin (a cousin from a parent's same-sex sibling) may be considered incestuous, in others it might not be frowned upon, and indeed, in some cultures, marriage between certain kinds of cousins is preferred or even encouraged.