Gender Essentialism:

Gender essentialism, also called innate gender identity, is a discredited and outdated theory that gender is a fixed and innate—men and women have distinct, intrinsic qualities determined biologically, not culturally—basically equating gender and sex. It can have negative effects on society by reinforcing gender stereotypes and how relationships should work — creating gender-segregated labor markets as if certain jobs and tasks were more suitable for men or women — and making it difficult to make active choices about consent.