There are some studies with monkeys and chimps and depending on their biological gender they do prefer to play with dolls or so on. It is hard to say to what extent "chimp society" is conditioning them - I would say not that much as if I recall the dolls and boyish alternatives were placed there for the study so there shouldn't be much of a societal effect. At least to me those studies reinforce my pre-existing bias for thinking that gender isn't exclusively a social construction. At the very least I really think pregnancy and the easier breast feeding "breaks the symmetry" if nothing else (hormones?) does.
For example, in chimp society the girl chimps will possibly be emulating behaviour of the adult females:
http://news.nationalgeographic.com/news ... evolution/The study with monkeys is with introduced toys:
http://www.newscientist.com/article/dn1 ... 1YhmmSztXcIf you are interested you can google for more info on the studies and make your own conclusions.
It warrants much more research in my opinion, but I wouldn't be surprised that there is a small biological component that gets amplified significantly by society.
I certainly agree that to a great extent gender roles are mostly a social construction - I'm talking about stuff like watching sports "is for guys" or "cooking is for women". It is also my opinion that reinforcing that kind of stuff is pervasive and sometimes it is even hard to notice that some conditioning is happening (but it is). I think it was even in this forum that I read someone giving an example: a baby girl picks up "girl toys", the grandparents find it cute and smile at her. Conversely they don't pay much attention to the baby if she picks up boys' toys. That is extremely subtle but is already conditioning.
Whether that is in the end positive or detrimental to society as a whole is a different topic. I think a lot of women are actually very happy about the status quo (and actually a lot of discrimination against women going against societal gender roles comes from other women, perhaps more so than from men). Same goes for men, and those that go against societal gender roles getting lots of backlash from other men. This doesn't mean it doesn't suck for the minorities challenging the societal roles but at least it makes one wonder if the "oppressive" majority is indeed being well served by the societal gender roles.