Throughout history, nearly all the people who ordered wars and fought in wars were men, not women. Why Men Make War explains the bio-science behind that distinction-from small differences in the brain, to huge differences in aggression-inciting hormones-all leading to specific traits that prompt women to act for peace, instead of war.

The book takes off with a timely discussion of what makes a man-10 traits that have defined masculinity for thousands of years. It documents the high frequency of wars (28 U.S. wars since 1775) and men's obsessive drive for ever-more-lethal weapons, now intensified by the power of artificial intelligence.

Evolutionary and biological evidence indicates the world will have less war when women have as much political power as men. The book closes by outlining a program to help women achieve that goal.