You mean their sex, not their gender. Gender as a concept hadn't even been invented yet: > Sexologist John Money introduced the terminological distinction betw

You mean their sex, not their gender. Gender as a concept hadn't even been invented yet: > Sexologist John Money introduced the terminological distinction between biological sex and gender as a role in 1955. Before his work, it was uncommon to use the word gender to refer to anything but grammatical categories.[1][2] However, Money's meaning of the word did not become widespread until the 1970s, when feminist theory embraced the concept of a distinction between biological sex and the social construct of gender. From the Wikipedia page for gender