I mentioned in another post but one of the inspirations for this thread is a trans woman who describes herself as not super effeminate, and didn't like dresses and makeup. So it was super cool to talk with her about challenging this cultural preconception that female identity =/= femininity > masculinity.
I think there are several ways in which it is suspect -- even ridiculous -- to conform ourselves to social stereotypes of what is masculine and feminine. Such things are largely arbitrary anyway. To blindly conform oneself to them is to unnecessarily limit the range of ones adaptive behaviors.
At the same time, I think it is nearly certain that masculinity and femininity have some sort of genetic component to them. It might sound paradoxical to believe that concepts of masculinity and femininity are both largely arbitrary and to some significant extent genetically based, but the paradox is solved when one looks into the details.
Take as an example something that clearly must be rooted in human instinct and therefore have a genetic basis of some sort: Tool use. There is not a culture on earth that doesn't make extensive use of tools of some sort or another. For that and other reasons, it is almost certain the predisposition to use tools, the instinct to use things as tools, must be genetically based.
Yet does that mean that any specific tool or kind of tool is hardwired into our genes? Of course not. With the possible exception of a basic hammer or hammer-like tool, and maybe a spear of some sort, few if any of our tools seem even in the least hardwired into us. There is no gene or genes that predispose us to create saws, for instance, no internal template for them.
In much the same manner, I believe it likely that some sort of predisposition or instinct for masculinity and some sort of predisposition or instinct for femininity might also be hardwired into us -- even if that hard wiring amounts to little more in practice than a marked, an ingrained and pronounced tendency to see the sexes as defined in contrasting comparison to each other, or some other such nebulous thing. Yet at the same time, how we choose to define those predispositions might be quite largely or wholly arbitrary matters, near entirely cultural and individual matters.
Where it gets complex for me is in the fact that so many of us show both masculine and feminine traits. But perhaps that is easily explained. If it really is true that how we define masculinity and femininity is largely or entirely cultural and individual, then why shouldn't we expect there to be people who possess both sets of traits? It would only be truly problematic if there were no such individuals and yet everything was still more or less culturally and individually defined.