Well let's see if I can give some counterexamples... First, I would argue that historically, and I mean for all of recorded history, the distinctions between men and women, the masculine and the feminine, the yin and the yang, Norman Rockwell’s right angles and smooth curves, have been recognized. This idea of sameness is a new concept for most cultures. What's more, many people have argued against even differences in physical abilities. This would seem to leave no reason whatsoever for the long history of patriarchal cultures, and male physical dominance in humans and apes.
Can anyone really dispute that by far, on the average, little boys are more aggressive, and more difficult to manage than little girls; and that boys are often quite found of tormenting girls but not the reverse? I know I sure was; and I did...every chance I got! Can anyone really equate a 15 year old boy to a girl of the same age? Young men and women are both driven by hormones, but there is a difference. If there wasn't, then my teen years would have been much less...um...lonely...restrained...right handed. Boy I would have sold my soul to find a girl with my sex drive!...when I was 16. Most young men that I knew were about the same more or less. One of the few guys that I knew that was not really really really desirous of girls turned out to be gay.
Now, after being married for 17 years and together with my wife for 20 years, I am convinced that I am only starting to realize just how fundamentally different we are. We have always had an intense relationship. We are both stubborn and opinionated. But many problems that we struggled with for years really came down to communication. We actually had one recurring fight [verbal only, things have never gotten out of hand] that, only after ten years of going round and round did I realized that we were each fighting about something different. The disagreement did not even exist!
I have also grown to believe that most communication problems that we have had originate in a fundamental mechanism of perception. I used to think that my wife was just being difficult, unreasonable, stubborn, single minded, or intentionally contrary. Now I understand that this perception stems from the huge void between her perception of the world and mine. I have also learned from other couples that most have endured the same difficulties. What is more, the men have mostly the same complaints about their wives, and the women agree equally about THOSE MEN. And don't deny it girls...I have heard it all!
I would add that most 16 year old young men would be shocked to hear the discussions that go on in girls locker rooms. My wife finally confessed.