Yeah. It's the context of it though. I doubt there were any Spartans crying on the battlefield for instance. Of course simply stating 'boys don't cry' is a social construct. It is very much a concept. As I mentioned in another thread though, it seems to me about making yourself appear strong. Crying is a sign of weakness. If you were punched in the face and you burst out crying, the attacker would see that as a sign of weakness.
It goes beyond simply crying though. It is perhaps about making yourself appear strong and big both physically and metaphorically as a form of intimidation. To nullify a potential threat.
You know, nurture in itself is strangely paradoxical. Nurture is the most natural thing you can do. Most animals nurture their offspring. A lion's cub has to watch its mother to learn how to hunt, yet the impulse to hunt is very much an instinctual thing. Of course our brains are basically in learning mode in our early years. The very reason for that is so we absorb that crucial training and learning to give us the best possible chance for survival. Perhaps we're hard-wired to observe and learn from other people of the same gender.
I mean even language is a social construct, yet the act of communicating is one of the most natural things we can do. All languages are different. All languages are changing and evolving. The act of creating a language, a way in which to communicate, is a natural process though.
Nurture and nature are very much entwined in our nature.