It may seem a stretch to move from primate behavior to religion and humanism, but there is a logic to it. My interest in these issues started with studies on primate cooperation and conflict resolution, which led me to think about the evolution of empathy and, ultimately, human morality. My first book on this topic, Good Natured (1996), barely mentioned religion, but there are many people for whom morality and religion are inseparable, whereas others contest this connection. I felt it was time to add religious and nonreligious outlooks on life to the mix. They are essential to answering the question why our species so readily divides behavior into right and wrong.
There is also the inclusion of Hieronymus Bosch, who for me has always been a background presence. I named one of the Arnhem chimpanzees, Yeroen, after Bosch, whose first name in Dutch is Jeroen. Knowing my affection for the painter, students who worked with me at the time, in the 1970s, surprised me after my Ph.D. defense with a richly illustrated book on Bosch. Marianne Oertl, a German journalist and a painter herself, added to my interest by illuminating the connection between Bosch and my view of human nature. She saw him as an early humanist, which is also how I portray him in The Bonobo and the Atheist.
In 2009, the American anthropologist Sarah Hrdy and I received honorary doctorates from the University for Humanistics, in Utrecht, which further stimulated my exploration of the humanist angle in discussions with the philosopher Harry Kunneman and others. But, of course, the chief source of my approach to morality has always been my scientific work on the prosocial side of animal behavior. The decades of research that went into this book involved far too many co-workers, students, and funding sources to be mentioned by name. Let me thank my most recent collaborators and team members, who contributed to the findings reported, including the real-life stories that enliven my accounts: Kristin Bonnie, Sarah Brosnan, Sarah Calcutt, Matthew Campbell, Devyn Carter, Zanna Clay, Marietta Dindo, Tim Eppley, Pier Francesco Ferrari, Katie Hall, Victoria Horner, Kristi Leimgruber, Tara McKenney, Teresa Romero, Malini Suchak, Joshua Plotnik, Jennifer Pokorny, Amy Pollick, Darby Proctor, Diana Reiss, Taylor Rubin, Andy Whiten, and Yuko Hattori. I am grateful to the Yerkes National Primate Research Center of Emory University for the opportunity to conduct our studies, and feel grateful to the many monkeys and apes who have participated and become part of my life.
I have over the years interacted with many philosophers, who have sharpened my sense of how their discipline approaches morality. Philosophers have thought about it for several millennia, whereas biologists have only just begun. I thank all of them as well as other experts and friends for their advice and comments on parts of the manuscript: Isabel Behncke, Nathan Bupp, Patricia Churchland, Bettina Cothran, Peter Derkx, Ursula Goodenough, Orin Harman, Sarah Hrdy, Philip Kitcher, Harry Kunneman, Robert McCauley, Ara Norenzayan, Jared Rothstein, and Christopher Ryan. Thomas Vriens of the Jheronimus Bosch Art Center, in Den Bosch, fact-checked some of the sections on the painter, even though I remain solely responsible for the interpretations.
I thank my agent Michelle Tessler for her continued support, and my editor at Norton, Angela von der Lippe, for critical reading of the manuscript. As always, however, the commentator-in-chief has been Catherine, my wife, who eagerly reads my daily production and helps improve the text with her honest opinions. Even better, she pampers me and makes me a happy man.