Ernst Mayr (ĕrnst mīr), 1904–2005, American zoologist and author, b. Kempten, Germany. He began his career in Berlin and emigrated to the United States in 1931, where, until 1953, he was associated with the American Museum of Natural History in New York. From 1953 to 1975 he was professor of zoology at Harvard. In 1940, Mayr refined the definition of the term species to "groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups." Along with Theodosius Dobzhansky and George Gaylord Simpson, he helped formulate the synthetic theory of evolution, putting together the theories of Charles Darwin and the genetic principles of Gregor Mendel. Mayr was also a noted ornithologist and a pioneer in the study of the history and philosophy of biology. His books include Animal Species and Evolution (1963), The Growth of Biological Thought (1982), Principles of Systematic Zoology (1980), This Is Biology (1997), and What Evolution Is (2001).