There are plenty of cultures around the world that conceptualize gender differently than we do, as well. Including many where there are options where individuals can choose their gender, in various circumstances or for various purposes.

So actually on the scale of human evolution, humans have been making different choices about matters like these since we've been humans.

It's really not new or recent. For as long as there's been gender norms there's been groups of people outside those norms.

You can, for example, find examples of trans individuals in Utah in the 1800s. [1] Eunuchs are a pretty well-known concept since about the start of recorded history.

Here's an example of a roman cult which practiced self-castration. [2]

[1] https://en.wikipedia.org/wiki/B._Morris_Young

[2] https://en.wikipedia.org/wiki/Galli

I didn't mean to imply that these people didn't exist, just that the scientific understanding detailing aspects of their existence (chromosomes, gonadal dysgenesis, etc) is new.

> Societal gender norms have existed for probably as long as humans have

Or gender norms have existed since gender was defined in the 70s-80s by feminist scholars. Before that was only sex, which biologists know to be not a binary but a bimodal distribution, itself.

That sound you hear is literally every anthropologist laughing hysterically.

Norms are not defined by scholars or scientists, even if they may define the terms to describe them.