“As recent work on the construction of gender has demonstrated, any strict dispensation may be historically precipitous. Neither heterosexuality nor homosexuality existed as categories in early modern Europe, for the simple reason that neither the standard nor its deviation(s) had yet been prescribed. The latter-day incontrovertible male/female binary […] was not yet in place. In addition to a two-sex model, Thomas Laqueur has documented the Galenic one-sex model that obtained in the Renaissance. In this model women were viewed as incomplete men, though, as Stephen Orgel has recently proposed, at the same time that this model privileges man over woman, it also threatens male identity with the possibility that “we are all, in essence, really women.”
Further, one need only turn to the official grammar book of the period for the suggestion that there were neither one nor two but rather many categories of gender; William Lily’s Latin Grammar, the only grammar prescribed in schools in Shakespeare’s time, classifies nouns into seven genders, including male, female, neuter (neither male nor female), doubtful gender (either male or female), and epicene (both male and female).”
"The Materiality of the Shakespearean Text" by Margreta de Grazia and Peter Stallybras (Shakespeare Quarterly 44.3, 1993).