I posted this in another thread but I think it also fits here:
Whilst, I think, it is undoubtable gender perceptions are strongly influenced by culture, variance across different societies is testimony to this, I do believe there is some cross over as there is a complex interaction between biological and cultural influences, generally. For example different levels of sex hormones have been shown to affect behaviour, the link between testosterone and aggression and Pre-Menstrual Psychosis illustrates this, but whilst variant hormone levels might mean someone is pre disposed to certain behaviours, it does not mean engaging in these behaviours is a pre-requisite. I actually also read a study in New Scientist that noted different hormones levels amongst men in different societies and linked this to aggression. Added to this, persistent patterns of behaviour, experience and thought patterns can actually alter brain physiology and environment can affect gene expression.
So there is a complex interplay between biology and culture, nature and nurture. Thus it would follow that there might be a complex interplay between some sex determined biological differences (which might also differ between different societies) and gender expression. I don't just think all sexually determined differences are distinct enough, because there is variance within the same sex and across different cultures, to label them purely biological differences. Equally, I think, because some less distinct sex determined biological differences can be explained biologically, we cannot say they are purely cultural.
Don't get me wrong, I still think ideas of gender undoubtedly vary across societies and throughout history, thus have a strong cultural influence. However I think we are only just finding out how our biology predisposes us to all sorts of things as well as how our own choices can affect this biology throughout generations.
Where this leaves people, I don't know.