COVER—Jesse Durocher/Getty Images; 1—Courtesy Bonampak Documentation Project, illustrations by Heather Hurst and Leonard Ashby; 3—(clockwise from top left) Helge Andersson, Courtesy Alexander Pryor/University of Exeter, Courtesy Finding Eanswythe, Institute of Archaeology in Belgrade, travellinglight/Alamy Stock Photo; 4—Azoor Photo Collection/Alamy Stock Photo; 8—Bridgeman Images; 9—Helge Andersson; 10—travellinglight/Alamy Stock Photo; 12—Courtesy Alexander Pryor/University of Exeter (2), R.J. Clarke (2); 14—Courtesy Finding Eanswythe (2), ©Mark Hourahane/Diocese of Canterbury, Formative Etlatongo Project; 17—Dr. Nicole Spaulding, Climate Change Institute, University of Maine; 19—Institute of Archaeology in Belgrade (2); 20—Photo by Junkai Yang, Photo by Songmei Hu, M-H. Moncel (2); 22—(clockwise from top left) Wikimedia Commons, Wikimedia Commons, Peter Horree/Alamy Stock Photo, Courtesy José Capriles/Penn State University, Brown University; 23—(clockwise from top left) Courtesy Anagnostis P. Agelarakis/Adelphi University, S. Saleem, Andrew Thomson/Griffith University, Heather Burke, 2020…