Not specific gender roles such as pink for girls and blue for boys, but more general gender roles such as that men are dominating and leader of the family while women are nurturing and caretakers.
hi! it might be worth x-posting this question to /r/AskAnthropology or /r/AskSocialScience
I recommend the book http://www.warandgender.com/
Generally speaking war is a plausible explanation, and you can derive everything else from that.
Chapter 1: http://www.warandgender.com/wgch1.htm