Part of it is social conditioning; females are more inclined to doing things socially more so than they already are because they are encouraged by their parents and the people around them to do so; and same with males. Who's buying the toys for the kids? The parents are. Who's buying the clothes? Also the parents. And you see role models and figures of people that would typically be associated with being a particular gender; most children, who are impressionable, are influenced by them.
Genetics and social conditioning aside, it is still possible for a female to appear to have characteristics more commonly associated with being male and vice versa; Sophie Germain was a French mathematician who was discouraged by her parents from studying math. But she did it anyways, with sympathetic male colleagues and candelight reading at night when her parents weren't aware of it. In fact, she impressed the heck out of the genius mathematician, Gauss.
Genetics and social conditioning aside, it is still possible for a female to appear to have characteristics more commonly associated with being male and vice versa; Sophie Germain was a French mathematician who was discouraged by her parents from studying math. But she did it anyways, with sympathetic male colleagues and candelight reading at night when her parents weren't aware of it. In fact, she impressed the heck out of the genius mathematician, Gauss.