One-sex and two-sex theories

The one-sex and two-sex theories (also referred to as the one-sex and two-sex models) are historiographical concepts introduced by historian Thomas Laqueur in his 1990 book Making Sex: Body and Gender from the Greeks to Freud. Laqueur proposed that Western medical and philosophical thought underwent a fundamental shift in the 18th century: from a "one-sex model," in which female anatomy was understood as an inverted, inferior version of male anatomy, to a "two-sex model" treating men and women as anatomically distinct and opposite.

Source: Wikipedia — One-sex and two-sex theories (CC BY-SA 4.0)