George G. Simpson (1902-1984) had an enormously successful career for some 50 years during the middle of the twentieth century. Owing to his great intellect, especially his deep analytic skill and broad synthetic insight as well as his single-minded persistence, he produced a large body of published work that became an integral part of modern evolutionary theory. His high level of scientific achievement can be measured by the number and quality of publications, institutional affiliations, honors and awards received, and recognition by the mainstream popular culture. But as David Hull has emphasized, "Unless one pays attention to [the professional relations among scientists], one cannot begin to understand science." To understand Simpson-the-scientist one has to know the social ecology within which he operated, starting with his Colorado playmate and second wife Anne Roe, who convinced him of the value of using small sample statistics in his study of species; Arthur Tieje, a geology instructor at the University of Colorado who encouraged his youthful intellectual ambitions; the opportunities at Yale where he studied under R. S. Lull and discovered a cache of Mesozoic mammals that became the subject of his dissertation; an early field season with W. D. Mathew who then became his mentor; a postgraduate year at the British Museum where he became part of the international paleontological network; and his first employment at the American Museum of Natural History with its extensive collections and library where H. F. Osborn and W. K. Gregory influenced him as did a benefactor, Horace Scarritt, who financed several of Simpson's field expeditions. Others, however, had negative impact on him, including his first wife Lydia Pedroja, the AMNH director Albert Parr, and another museum benefactor and researcher, Childs Frick