[einhverfr]

Structuralists and Post-structuralists though tend to see most cultural constructs as arbitrary on an atomic level, and to the extent they are useful to a group that comes out of context with other cultural constructs. So for example the fact that we associate pink with girls and blue with boys is entirely arbitrary. It could be (and indeed historically has been until surprisingly recently) the other way around.

With humans though the linking of physical sex and gender is not as simple as you suggest. As I have said, some cultures (like ours) have two genders. Some have three, with children being genderless, and some have more genders than three. To pretend that gender is only about display of sex-based characteristics is to gloss over the fact that in most cultures it doesn't really work that way, nor does it really even in our own.

Gender is instead a social category and a social position. It affects division of labor and all sorts of other things. Different genders often have different taboos and these are often aimed at preventing gender-crossing, as well as maintaining a symbolic order between genders.

This is a very broad category of anthropology, and it's dangerous to assume that everyone structures their society around two genders fairly closely tied to biological sex, since this is not really the case.