specializing in mammalian evolution, who also studied mammal migrations, Simpson obtained his Ph.D. from Yale University in 1926, for a thesis on Mesozoic mammals, and then joined the staff of the American Museum of Natural History, in New York City, becoming curator in 1942. In 1945 he moved, as a professor, to Columbia University. From 1959 to 1970 he was Alexander Agassiz Professor of Vertebrate Palaeontology at the Museum of Comparative Zoology at Harvard University, and in 1967 was appointed professor of geosciences at the University of Arizona. His studies of fossil mammals, especially those of Madagascar, led him initially to oppose the theory of continental drift. Simpson proposed that the dispersion of species occurred along sweepstakes dispersal routes.