Today on MindMatters we discuss complexity scientist Peter Turchin's 2015 book, Ultrasociety: How 10,000 Years of War Made Humans the Greatest Cooperators on Earth. Turchin walks us through 10 millennia of human cultural evolution: from tribes and chiefdoms to the first states and empires, to our modern "ultrasocial" states. Contrary to pet theories and many ingenious hypotheses over the generations, the development of large, complex societies was not the result of agriculture or even ideas--the primer driver has been warfare: the technologies humans have developed to defend and conquer, the cooperation needed for both, and the cultural practices and values that developed and survived as a result.