In The Better Angels of Our Nature, Pinker presents data showing that human violence, while is still very much with us today, has been gradually declining. Moreover, he says, "over the long sweep of history, women have been and will be a pacifying force. Traditional war is a man's game: tribal women never band together to raid neighboring villages." As mothers, women have evolutionary incentives to maintain peaceful conditions in which to nurture their offspring and ensure that their genes survive into the next generation. 

Skeptics immediately reply that women have not made war simply because they have rarely been in power. If they were empowered as leaders, ....'