George Gaylord Simpson Bibliography

George Gaylord Simpson, (born June 16, 1902, Chicago, Ill., U.S.—died Oct. 6, 1984, Tucson, Ariz.), American paleontologist known for his contributions to evolutionary theory and to the understanding of intercontinental migrations of animal species in past geological times.

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Simpson received a doctorate from Yale University in 1926. He chose for the subject of his thesis the mammals of the Mesozoic Era, which are important for the understanding of mammalian evolution, although evidence of their existence consists mainly of tantalizing fragments of jaws and teeth. The materials were located chiefly in the Peabody Museum at Yale and the British Museum in London. Simpson produced substantial quarto monographs on the two collections, making his reputation as an able worker in mammalian paleontology.

In 1927 he joined the staff of the American Museum of Natural History, New York City, where he was to continue research in paleontology for three decades. The first 15 years were highly productive; he published about 150 scientific papers, many of considerable importance. A few dealt with lower vertebrates, but nearly all were on mammalian paleontology. In his first years in New York City he was interested in the fauna of Florida of the Neogene Period and the Pleistocene Epoch (the Pleistocene, which followed the Neogene Period, began about 2.6 million years ago and ended about 11,700 years ago). He published a number of works on this topic. For the most part, however, his interests were in the early history of mammals, and most of his publications in the 1930s were concerned with this field. He studied the Cretaceous mammals of Mongolia and North America, especially the Paleocene fauna of the latter continent (the Paleocene Epoch began about 65.5 million years ago and ended about 55.8 million years ago). This resulted in a major work on the Paleocene fauna of the Fort Union Formation of Montana, in which about 50 mammals of a variety of primitive types were found. The breadth of his studies of mammalian evolution led to the writing of a detailed classification of mammals that is standard in the field.

In the early Cenozoic a series of mammalian fauna lived in South America that were quite unlike those of any other continent. Those of the Neogene and Pleistocene forms were fairly well known, but little was known of the earlier history of the peculiar South American groups. Hence, in the early 1930s he made three expeditions to Patagonia to collect new material and re-study specimens already described; as a result of these efforts, the early history of the Neogene mammals of South America became vastly better known. He published several dozen papers on these forms in the late 1930s and afterward two volumes summarizing their early history.

During World War II Simpson did staff work for the U.S. Army, principally in North Africa. On his return to the American Museum, he became curator in charge of the active department of paleontology, as well as a professor at Columbia University. This restricted the time available for research, but his scientific productivity remained undiminished. While his descriptive work in paleontology continued, his interests spread to other fields. The possibility of applying mathematical methods to paleontology had already led to his coauthorship of a work on quantitative zoology. A consideration of the successive faunas of the various continental areas led to studies of the problems of the intercontinental migrations of animal species. Problems of taxonomy and classification are intimately connected with evolutionary studies, and, in addition to giving a thorough consideration of principles of classification in his work on mammalian classification, he published in 1961 a volume on The Principles of Animal Taxonomy. In a series of lectures which appeared in book form as The Meaning of Evolution in 1949, he discussed the philosophical implications of the acceptance of evolutionary theory, which attracted worldwide attention. In the postwar period there was a renewed study of evolutionary theory by geneticists, systematists, and paleontologists. Simpson took a major part in such studies; his principal publications in the area were his volumes Tempo and Mode in Evolution (1944; reissued 1984) and Major Features of Evolution (1953).

In 1958 Simpson left New York City to spend a decade as an Alexander Agassiz Professor of Vertebrate Paleontology at the Harvard Museum of Comparative Zoology. After that he moved to Tucson, Ariz., where he became professor of geosciences at the University of Arizona, a post from which he retired in 1982. He continued to publish widely. Later works include Splendid Isolation: The Curious History of South American Mammals (1980), Why and How: Some Problems and Methods in Historical Biology (1980), and Fossils and the History of Life (1983).

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George Gaylord Simpson (June 16, 1902 – October 6, 1984) was one the most influential paleontologist of the twentieth century and a major figure in the modern evolutionary synthesis, helping to integrate paleontology into this newly emerging synthetic theory. His works, Tempo and Mode in Evolution (1944) and Principles of Classification and a Classification of Mammals (1945), were particularly instrumental in this respect.

An expert on extinctmammals and their intercontinental migrations, Simpson is also noted for dispelling the view that the evolution of the horse was a linear process culminating in the modern Equus caballus and for anticipating such concepts as punctuated equilibrium.

One of Simpson's famous quotes is, "man is the result of a purposeless and natural process that did not have him in mind." This is one of the dogmas in evolutionary science. It involves an almost religious-like belief, since in reality, while there is a lot of evidence for the theory of descent with modification (the pattern of evolution), the theory of evolution by natural selection (the process or mechanism) on the macroevolutionary level remain an unproven extrapolation from processes on the microevolutionary levels.


Early years

George Gaylord Simpson was in Chicago on June 16, 1902, the first son and third and last child of Joseph A. Simpson, a lawyer, and Helen J. (Kinney) Simpson (Laporte). His father handled railroad claims as an attorney, but became involved in land speculation and mining, which led to there moving briefly to Wyoming, and then in 1903, to Denver (Laporte 2007b). Simpson had a strict, fundamental Presbyterian upbring, but was to reject formal religion by the early teens (Laporte).

In 1910, he talked his parents into the purchase of the eleventh edition of the Encyclopedia Britannica, which he contributed to the purchase of, and he read it straight through (Laporte 2007b, 2007c). He graduated from elementary school in 1914, at the age of 11, having completed 8 grades in 6 years, and graduated high school in 1918, close to his sixteenth birthday.

In 1918, at the age of 16, Simpson entered the University of Colorado at Boulder, but his father lost his mine in Alma, Colorado, and with the family finances at a low point, he briefly dropped out (Laporte 2007b). After returning to the University of Colorado, he stayed until his senior year, 1922, when he transfered to Yale because he was advised it was the best place to study geology and paleontology. In 1923, he secretly married Lydia Pedroja, despite it being contrary to Yale's regulations. In June, 1926, he completed his Ph.D. in geology in Yale.

Professional life

In 1927, Simpson took a position as assistant curator in vertebrate paleontology at the American Museum of Natural History and in 1928, was promoted to associate curator. By 1932, Simpson was formally separated form Lydia and had custody of one daughter, Helen, while one daughter lived with the maternal grandmother, and his two other daughters with Lydia were under her custody (Laporte 2007c). However, in late 1932, Lydia was committed to a mental hospital and Simpson's parents cared for these two daughters. Lydia had had a history of mental problems even before meeting Simpson (Laporte 2007b). In 1932, Simpson began to live with Anne Roe, a childhood friend, who also had obtained a Ph.D., from Columbia University in psychology, and had divorced her husband in 1932. Simpson would gain a divorce from Lydia in April 1938, and marry Anne a month later (Laporte 2007b).

In 1942, Simpson became the first elected President of Society of Vertebrate Paleontology. In 1942, after the Director of the American Museum of Natural History disbanded the department of vertebrate paleontology, to Simpson's dismay, he was promoted to curator of fossil mammals, but in December of that year he started duty with the U.S. Army as a captain in military intelligence—after completing a six-week course in one week (Laporte 2007c). In August 1944, slowly recovering from a hepatitis infection, Major Simpson was released from duty with two Bronze Stars. The same year, Simpson became the chairman of the newly created Department of Geology and Paleontology at the American Museum of Natural History, and in 1945, he also took a position as professor of vertebrate paleontology in the department of zoology at Columbia University.

Simpson's classic work, Tempo and Mode in Evolution, was published in 1944. In this work, he integrated paleontology within the modern evolutionary synthesis (Hull 1988). In 1949, he published a popular account of modern evolutionary theory from the point of view of paleontology, The Meaning of Evolution, which was to become widely sold and translated into ten languages.

Simpson was Professor of zoology at Columbia University and curator of the Department of Geology and Paleontology at the American Museum of Natural History from 1945 to 1959. In 1958, he gave up chairmanship of the Department and resigned shortly thereafter from the American Museum, taking an appointment as professor at the Museum of Comparative Zoology of Harvard University. He was curator of the Museum of Comparative Zoology at Harvard University from 1959 to 1970.

In 1963, when Anne was made a professor at Harvard University, Simpson and his wife became the first husband-wife couple to be full professors at Harvard (Laporte 2007c).

In 1968, Simpson was appointed professor of Geosciences at the University of Arizona, from which he retired in 1982, at the age of 80. He continued part-time with the Museum of Comparative Zoology at Harvard until 1970 as well.

In 1984, Simpson's final book, Discoverers of the Lost World, was published, which, like his first, Attending Marvels, is about South America (Laporte 2007c). On Saturday, October 6, Simpson died of heart failure in a Tuscon hospital. A manuscript he was working on, dealing with extinction, was posthumously published the next year.


Stephen J. Gould summarized the catch-22 of his personality (Hull 1988):

He couldn't tolerate a toady, for his intellectual honesty was too great and his perceptions too acute to misidentify this genre. But neither could he bear disagreement, however gently expressed. He took offense easily, placing the worse possible interpretation on any event that displeased him. This bitterness seemed so inconsistent with the grandeur of his prose, the generosity of his vision, the warm and expansive humanism of his general writings.


"Man is the result of a purposeless and natural process that did not have him in mind" (Simpson 1967, p. 345). "I don't think that evolution is supremely important because it is my specialty; it is my specialty because I think it is supremely important" (Larson 2004). "The regular absence of transitional forms is not confined to mammals, but is an almost universal phenomenon, as has long been noted by paleontologists."


  • Attending Marvels (1931)
  • Mammals and Land Bridges (1940)
  • Tempo and Mode in Evolution (1944)
  • The Meaning of Evolution (1949)
  • Horses (1951)
  • Evolution and Geography (1953)
  • The Major Features of Evolution (1953)
  • Life: An Introduction to Biology (1957)
  • Principles of Animal Taxonomy (1961)
  • This View of Life (1964)
  • The Geography of Evolution (1965)
  • Penguins (1976)
  • Concession to the Improbable (1978)
  • Splendid Isolation (1980)
  • The Dechronization of Sam Magruder (posthumously published novella, 1996)


  • Gould, S. J. 2002. The Structure of Evolutionary Theory. Cambridge, MA: The Belknap Press of Harvard University Press.
  • Gould, S. J. 2007. George Gaylord Simpson. The Stephen Jay Gould Archive. Retrieved December 22, 2007.
  • Hull, D. L. 1988. Science as a Process: An Evolutionary Account of the Social and Conceptual Development of Science. Chicago: The University of Chicago Press.
  • Laporte, L. F. 2007a. George Gaylord Simpson: Introduction. UC Santa Cruz: Information Technology Services. Retrieved December 22, 2007.
  • Laporte, L. F. 2007b. George Gaylord Simpson: Biography. UC Santa Cruz: Information Technology Services. Retrieved December 22, 2007.
  • Laporte, L. F. 2007c. George Gaylord Simpson: Chronology. UC Santa Cruz: Information Technology Services. Retrieved December 22, 2007.
  • Larson, E. J. 2004. Evolution. Modern Library. ISBN 0679642889
  • Miller, R. 1990. George Gaylord Simpson. In R. Miller, The Encyclopedia of Evolution. New York: Facts on File. ISBN 0816014728
  • Public Broadcasting Service. 2007. George Gaylord Simpson]. PBS. Retrieved December 22, 2007.
  • Simpson, G. G. 1967. The Meaning of Evolution. New Haven: Yale University Press.


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Reconstruction, left forefoot skeleton (third digit emphasized yellow) and longitudinal section of molars of selected prehistoric horses. Simpson's detailed analysis in Horse (1951) countered the popular idea of a single-line of evolution of the horse from a fox-sized hoofless ancestor (Miller 1990).


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