I think this is begging the question a bit, though. Why would there be an assumption that there are "male" and "female" traits, or indeed differentiated gender roles generally, of not for some degree of inborn psychological (and therefore neurological/endocrinological) differences between men and women? I mean, human brains, or at any rate pre-human mammalian brains, have existed for millions of years before the advent of any human culture. Has there ever been a society that does not distinguish, in some way or another, between gender roles?
Note that this is a very far cry from there simply being a "linear, rational, male" way and a "holistic (whatever that means), intuitive, female" way of thinking - I think it's far more subtle and complex than that. But then, this is just my intuition, so it's probably best taken with a pinch of salt...