I should be careful about opining here, but this is a discussion that, as it happens, I’ve had recently with a couple of trans women.
Gender dysphoria–or at the very least, awareness of gender/sex mismatch—seems to be very old, given the number of attestations of gender-diverse instances in human societies, and of androgynous cultural artefacts.
What is new is the way that society—and individuals within that society—deal with gender dysphoria. That’s not just about veneration vs punishment from the social norm. That’s also about how individuals express a gender identity under dysphoria; what options their culture afforded them.
Some cultures had well accepted “third” genders. Some cultures had well established, even if not accepted, performative roles. In the West, even when gender reassignment became an option, being a street queen or transvestite were the default options in the 60s; the same people now would be be trans. Sylvia Rivera called herself gay till she died in 2002, and at the peak of her activism called herself transvestite. The disjunction of cross-dressing and trans identity is pretty solid now, but it was nebulous a couple of generations ago. The construals and options of gender, as social phenomena, have changed, even if the psychological and biological drivers behind dysphoria are the same.
I made the argument above to my friend Janna, that the dysphoria is old, but the social construals are new. And she made a very insightful point: the social construals have to be new. Because society is dynamic, in a way that biology is not.