George Gaylord Simpson

George Gaylord Simpson (16 June 1902 – 6 October 1984) was an American paleontologist. Simpson was perhaps the most influential paleontologist of the twentieth century, and a major participant in the modern evolutionary synthesis. 
He was an expert on extinct mammals and their migrations, especially the Great American Interchange between the Americas. Simpson opposed Alfred Wegener's theory of continental drift, so his work on animal migration lacked this idea.
Simpson dispelled the myth that the evolution of the horse was a linear process culminating in the modern "Equus caballus". He coined the word "hypodigm" in 1940, and published extensively on the taxonomy of fossil and living mammals.
Biography.
Born in Chicago, Illinois, Simpson was raised mostly in Denver, Colorado. He got his degrees from Yale University in 1923 and 1926. His dissertation, "American Mesozoic Mammalia" (1929), was the first step in his lifelong interest in the evolution of mammals. After a post-doctoral year at the British Natural History Museum, Simpson returned in 1927 to take up a post in the American Museum of Natural History.
In 1942, Simpson enlisted in the U.S. Army. He served as a Captain, then Major, in Army intelligence, Simpson served with American forces in North Africa and western Europe until 1944. Then he resigned, suffering from a severe bout of hepatitis. He returned home, with two Bronze Stars. He was promoted to Curator (head) of the Department of Geology and Paleontology at the American Museum of Natural History. He also held a post as Professor of Zoology at Columbia University (19451959). He took up his work on early mammals, and worked on the Palaeocene and Eocene faunas of the San Juan Basin, New Mexico. 
He was Curator of the Museum of Comparative Zoology at Harvard University from 1959 to 1970, and a Professor of Geosciences at the University of Arizona until his retirement in 1982.
Major works and awards.
In the 1940s Simpson produced three major works. "Tempo and mode in evolution" (1944), "Principles of classification and a classification of mammals" (1945) and "The meaning of evolution" (1949). Simpson provided a popular account of modern evolutionary theory with emphasis on evidence from the fossil record.
Simpson was awarded the Linnean Society's Darwin-Wallace Medal in 1958. He also received the Royal Society's Darwin Medal "In recognition of his distinguished contributions to general evolutionary theory, based on a profound study of palaeontology, particularly of vertebrates" in 1962. He was awarded the U.S. National Medal of Science in 1965.
Quotes.
These quotations from Simpson give a good idea of the man: