Actually, I think your observations show the opposite: i.e. the strength of socialization. Suppose I didn't know your child's gender. The behaviour you describ

Actually, I think your observations show the opposite: i.e. the strength of socialization. Suppose I didn't know your child's gender. The behaviour you described would not sound particularly male or female to me, given my biases. On the other hand, I infer that for you this appears to be typically "boyish" behaviour, and you use this as evidence of strong in-born gender traits. I.e. my daughter does exactly the same thing, but I didn't consider it "girlish". More "babies are duuuumb." One interesting thing about raising an infant is that everyone seems to project different things on to the child, and to have different interpretations of the same events. For instance, my wife and I focus on the fact that our daughter seems strong and smart. Others keep telling us how pretty she is. If she makes certain facial expressions, friends tell us it means one thing, while various relatives all have their own interpretations, that differ from our own interpretation. I don't think your observations confirm anything except your own biases. In case that sounds harsh, I think this is true of all of us. Note that I'm not making the strong claim that there are no gender differences. I just observe that there's much larger variation between individuals than between genders. Finally, I observe that parents treat girls and boys subtly differently even from before birth, and that this can't help but have an effect on their development.