Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A cultural universal (as discussed by George Murdock, Claude Lévi-Strauss, Donald Brown and others) is an element, pattern, trait, or institution that is common to all human cultures worldwide. Some anthropological and sociological theorists that take a cultural relativist perspective may deny the existence of cultural universals: the extent to which these universals are "cultural" in the narrow sense, or in fact biologically inherited behavior is an issue in the "nature versus nurture" controversy.