It's not my intention to purport that human males and females are exactly the same and essentially interchangeable. Clearly, we have some sexual dimorphism (although it's a lot less than many animals), and since cis women bear offspring and cis men do not, clearly there is some biological differences. But at the same time, there is no doubt that gender roles differ some from culture to culture and from era to era. In addition, there is no evidence that human brains are significantly different at birth as far as aptitudes, intelligence, capability for empathy, etc.
Because we are "higher" animals who have developed language and culture to a much greater extent than most other animals, we have the ability to create our culture more intentionally to be one that does not force anyone into a gender box that they do not wish to be in. Particularly since there is huge evidence that doing so is extremely detrimental - particularly to men. As I said in my OP, most cultures have gender roles, but in more egalitarian societies nobody cares all that much if everyone adheres to them as long as they contribute to the welfare of the group. Gender roles only become a problem when not adhering to them brings shaming, coercion, and violence - something that we tend to only see in patriarchal (dominance hierarchy) based cultures.
https://medium.com/inside-of-elle-beau/men-describe-what-it-takes-to-be-a-real-man-c694595b4366
On animals and culture, I'm reading a book called Becoming Wild right now that profiles various animal cultures. I'm learning all about sperm whales at the moment, and how much their cultures mimic that of elephants - where they are matriarchal, highly social, clan-based, etc. It's quite interesting to see how little of what they do is innate/instinct and how much is taught by elders and is different from clan to clan.
We are clearly a byproduct of both nurture and nature and it's hard to know for certain what the exact mix is. However, we do know an awful lot about the influence of our current culture (media, advertising, etc) as well as how that is different from other cultures in other parts of the world, as well as in other time periods. I'm not discounting the nature part - I just think we need to recognize that the nurture part is also extremely important and that the nature part is somewhat variable across individuals.
