1700: Randolph Trumbach: the construction of the heterosexual/homosexual sex/gender system, London
In his book Sex and the Gender Revolution: Heterosexuality and the Third Gender in Enlightenment London (Chicago: University of Chicago Press, 1998), historian Randolph Trumbach dates the construction of the heterosexual/homosexual sex/gender system to 1700 in London.
Contrast this with Jonathan Ned Katz in The Invention of Heterosexuality (NY: Dutton, 1995), who suggests that the development of the heterosexual/homosexual/bisexual organization of sexuality and gender as a historically specific system was roughly coterminus with the development and distribution of the terminology and ideas "heterosexual," "homosexual," and "bisexual."