Yes to the fact that humans are characterized by adaptability; yes to the observable fact that masculinity and femininity vary across cultures and time periods; and capital YES to the Duh - that if this stuff was so natural, why is it always being so heavily policed?

Way too many men have bought into the messaging that they are inherently different from girls and women - because "don't be a girl" is such a huge part of masculine identity. "Be a good human" feels like a loss - of both identity and the privileges that come with that identity to a lot of them. At least that's what I've encountered trying to talk to guys about this stuff. It's like these men have been sucked into a dodgy multi-level marketing scheme and they don't want to acknowledge that the whole thing is problematic because doing well in that MLM is such a huge part of what success looks and feels like to them. At least some men are intentionally moving away from this stuff, but a whole lot more would benefit from deprogramming from this sort of gender indoctrination - and women would as well.