Petersen AK. Peter Turchin, Ultrasociety: How 10,000 Years of War Made Humans the Greatest Cooperators on Earth (Chaplin, CT: Beresta Books, 2015), 274 pp. ISBN: 978-0-99613-953-3. $18.95 pbk, $9.95 ePub; Kindle. JCH. 2018;3(1-2):240-244. doi:10.1558/jch.33933