Traditionally, the term "gender" refers to the grammatical categories of masculine, feminine, and neuter, but in recent usage it refers more widely to sex-based social categories. Social scientists and anthropologists commonly distinguish gender, which is applied to social and cultural categories, from sex, which is reserved for biological categories. The distinction between sex and gender is underpinned by theories in the life and social sciences about the respective roles of nature and culture in the creation of human identity. Debates around sex and gender have tended to be controversial, and in recent years these have been intensified by medical and scientific research that has provided grounds both for and against the mapping of biological sex onto gender. Some of the most interesting perspectives on sex and gender have come from researchers studying intersexuality. In an influential paper published in 1993, biologist Anne Fausto-Sterling posits the existence of not two but five sexes—male, female, and three degrees of hermaphroditism. In the ensuing debate, which has practical bearings on gender assignment for hermaphrodite children as well as on a whole array of gender-rights issues, it has become clear that the variety of possible sexes and genders is greater than traditionally thought. Within most cultures, however, binary gender division is a persistent norm.