He was Professor of Zoology at the University of Chicago from 1929 until he retired in 1962. While at Chicago, Emerson was a coauthor of the synthetic opus, Principles of Animal Ecology (1949) by W.C. Allee et al., which was encyclopedic and credited with stimulating the nascent fields of population and community ecology. Emerson served as President of the Ecological Society of America in 1941, and as President of the Society of Systematic Zoology (now the Society for Systematic Biology) in 1958. He traveled widely and conducted numerous collecting expeditions. In 1940 he became a Research Associate of the AMNH, a position he held until his death in 1976. Alfred Emerson was a contemporary and colleague of various architects of the New Synthesis in evolution biology, including the ornithologist Ernst Mayr, the botanist G. Ledyard Stebbins, the paleontologist George Gaylord Simpson, and the geneticist Theodosius Dobzhansky (Mayr and Simpson both started their careers at the AMNH, then moved to Harvard). He was also a colleague of the influential ant biologist William Morton Wheeler (another Harvard professor whose early career was at the AMNH). Emerson and Wheeler each published a monograph on the termites and ants (respectively) of Zaire and Cameroon, among other areas; both men developed huge, global collections of these insects from their own field work and through acquisitions; and both promoted the concept of the insect colony as a superorganism. Emerson's taxonomy, however, has endured; Wheeler's practice of using subspecies and varieties was strongly rejected by later ant taxonomists. In recognition of Emerson's standing in the scientific community, he was also elected as president of the Society for the Study of Evolution in 1960, as a member of the National Academy of Sciences in 1962, and awarded "Eminent Ecologist" by the Ecological Society of America in 1967. Alfred Emerson remained scientifically active through his retirement until he died, on October 3, 1976 at Lake George, New York.