"What, or rather who, dictates that how one expresses themself or presents themselves to others must be contingent or follow some formulae or set of expectations[?]" --
I'd argue that no one dictates it, and that there is no specific formula. Gender identity and expression is entirely relevant on one's own experiences. One part of the world may view "girly" completely differently than another part, and hence someone who expresses themselves as "female" would express themselves differently based on what their culture is like. Basically, gender identity is how an individual understands gender, and where they place themselves in that understanding.
"Do you agree with the traditional or stereotypical assortment (ie. male: brashness, boldness. aggression/dominance?; female: whimsy, "daintiness", passivity/submission?) or something else?"
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There is something to be said for the effects of testosterone, and what that has done for society's view of what "male" means, but there have always been exceptions to the stereotypes, and I think everyone is free to interpret gender as they please.
"Who's to say in some fictional village the female inhabitants just so happened to have evolved larger and more "aggressive" than the male inhabitants who together in turn resemble a living antithesis of modern gender norms (ie. the females are larger, louder, more violent, let's say and the males are smaller, quiter, and more obedient or otherwise on average are submissive to the females). What about that sort of scenario?" --
This is exactly my point! In this kind of society, someone who portrays themselves as female might act more aggressive, louder, and those who express as male may be more submissive. Of course, stereotypes and gender may not be the same to all people, so I wouldn't be surprised to see some outliers portraying themselves as submissive females or dominant males (or something else entirely).
"Point being, it seems like you're referring to social constructs (that sure, obviously are derived from *circumstantial* biological norms) that still, can vary or change wildly depending on many circumstances." --
Yes. I believe that you are allowed to interpret gender in anyway you want, but that is typically shaped by how you grew up and the culture you were raised around. Perspective is shaped by experience, and that's why people who express themselves as male or female (or something else) tend to do so by portraying the stereotypical "traits" that are associated with the gender they identify with. It's simply what their view of being that gender means.
" Is that really reliable simply because it's all we know? Ignorance is not knowledge, now is it?"
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Not at all! That's what's beautiful about the world, in my opinion, that there is no "Right" answer, no way to ever truly know something. I'd argue that ignorance has to be knowledge, or else we know nothing. Science can't answer the questions of purpose, meaning, and morality. Science is simply us trying to understand the world we live in. Science is facts, and it is completely up to us to interpret those facts. You say that societal gender constructs are unreliable because they are how evolution randomly happened, and therefore are random, but can you say for sure that a divine hand did not guide said evolution? Can you say for sure that anything else could have happened? And even if something else could have happened, should we really include "what-ifs?" in our interpretation of the real world? Society and humanity have developed as they have, perhaps for a reason, perhaps by chance, but I say we should accept it as it is. There is no way to say whether these gender constructs are reliable or not, but they certainly do exist, and certainly need to be addressed in any interpretation of gender identity and expression.
"In philosophy we savagely attack ideas, not the persons who hold them."
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I know! Don't worry, I don't hold any ill-intent towards anyone just for having a different opinion than I. Everyone is allowed to interpret anything in their own way, and while I may disagree with it, there's typically no way to prove who is right when it comes to interpretation and opinion.
:D