Personally I think the whole idea that gender is something you are born with is stupid. Gender is a social construct, and it's a choice whether it's conscious or subconscious. There is not some DNA encoding that says girls are supposed to wear their hair long, or wear make up, wear skirts, etc...or something that says men cut their hair short, and so on...
At one time, men did wear their hair long because long flowing hair was a sign of masculinity, like a lion's mane. Gender identifiers change with the passage of time, and to say that we're born with traits of certain genders is nonsense, since gender identifiers have not been consistent throughout human history to begin with. You're either born with boy parts, or girl parts...that's it. How you choose to express and present yourself is all a fucking choice. A man who starts wearing dresses, and make up, and wants to be called "she" is not a woman...it's a man who wants to be seen with socially constructed feminine identifiers.
I'm okay with all of that, because I'm all for freedom of choice, but this idea that people are born with wanting to identify as the opposite sex is such nonsense to me since the whole idea of what is identifiable as man or woman is all constructed, and influenced by others after birth, and not inherited.
You're confusing 'gender' with 'gender expression' and 'cultural norms'.
While you're correct that fasions such as dress codes and hairstyles vary from era to era, let alone countries, there are fundamental behavioral differemces between genders driven by their biological sex that are what cause those gender expression norms to arise in the first place.
Girls prefer brighter colours, are more talkative and empathetic, while also tending to more complicated and often brutally cruel social interactions.
Boys are more active and aggressive and generally prefer mechanical and constructive pass times, and have more simplistic and violent social interactions, but with the benefit of that constant rowdy behavior quicker to defuse and move on from.
This can be demonstrated by simply offering a few days old baby a choice of toys. Put a doll and a truck infront if one, and 99.9 percent of the time the boy will want the thing with moving parts and the girl will want the thing with a face.
This is so universal that it even occurs in other great apes. Put the same toys infront of a Chimpanzee, Gorilla or Banobo, and you get the same results.
In fact this (at least used to be) part of the evidence gathering done to determine whether someone actually was transgender or simply suffering gender dismorphia. It's part of the reason we know that, as rare as it is, being trans is an actual physical condition and not just a mental illness.
So yeah, gender is absolutely real, you great transphobe you!
But seriously, all those things you mentioned as social constructs, they arise out of the fundamental differences and evolving tastes from one generation to the next precisely because genders exist, and drive those gender expressions to be created in the first place. You have the entire thing arse about face, sorry.
