Ultrasociety: How 10,000 Years of War Made Humans the Greatest Cooperators on Earth

Cooperation is powerful.

There aren’t many highly cooperative species—but they nearly cover the planet. Ants alone account for a quarter of all animal matter. Yet the human capacity to work together leaves every other species standing.

We organize ourselves into communities of hundreds of millions of individuals, inhabit every continent, and send people into space. Human beings are nature’s greatest team players. And the truly astounding thing is, we only started our steep climb to the top of...