"The Evolution of Cooperation", Martin Nowak, Professor of Biology and Mathematics at Harvard University and Director of the Program for Evolutionary Dynamics. Discusses: why cooperation, not competition, has always been the key to the evolution complexity; the mysteries of cooperation, from the rise of multicellular life to Good Samaritans, an from cancer treatment to the success of large companies; how cooperation, not competition, is the defining human trait. A Bemis Free Lecture.