Petersen, A. K. 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. https://doi.org/10.1558/jch.33933.