Ernst Mayr

The German-born American evolutionary biologist Ernst Mayr (born 1904) helped lead the modern synthesis of evolutionary theory. Mayr made major contributions to ornithology, evolutionary theory and the history and philosophy of biology. He is best known for his work on speciation—how one species arises from another.

Ernst Mayr was born in Kepten Germany, near the borders of Austria and Switzerland on July 5, 1904. He was one of three sons of Helene Pusinelli Mayr and Otto Mayr, who was a judge. The Mayr family valued education and Mayr and his brothers were provided with a broad education that included the study of Latin and Greek. All three sons became professionals. As a boy, Mayr developed a keen interest in birdwatching—an interest that remained with him for life. Mayr began to study medicine in 1923 at the University of Greifswald, but within two years he became so enthralled with the evolutionary works and studies of Charles Darwin that he switched his studies from medicine to zoology. His interest in birds had led him to the German ornithologist Erwin Stresemann, who induced him to make the switch to zoology. As his mentor, Stresemann had a great influence on Mayr's thinking as well as his career. Starting with his earliest work, Mayr saw the value of asking evolutionary questions in biogeographical studies, and he consistently argued for an evolutionary basis to species concepts. Conversely, he used biogeography and taxonomy in the effort to explain evolution where in 1926 he received his Ph.D. in zoology. Soon afterward he became the zoological museum's assistant curator.

Following his doctoral degree in zoology from the University of Berlin in 1926, Mayr became an assistant curator in the university's museum. His chance to explore was provided by the wealthy zoologist and collector Lord Walter Rothschild the next year when Mayr agreed to lead his expedition for ornithological exploration and collection in the mountains of Dutch New Guinea. Although the trip was not easy, his success gave him experience and fame in the ornithological world; invitations for expeditions immediately followed, including one to New Guinea for the University of Berlin and the Whitney South Sea expedition to the Solomon Islands for the American Museum of Natural History, New York. This led to his appointment to work on the collected material at the museum in New York. When the museum bought Rothschild's enormous bird collection in 1931, Mayr was an obvious choice for curator, and he became a permanent staff member—and a naturalized U.S. citizen. He married Margarete Simon in 1935; they had two daughters.

The experiences and insights crowded into these years in the South Pacific were to stimulate Mayr's thinking about biology and the development of species for decades to come. In a number of monographs during the 1930s, as he worked on the taxonomy of South Pacific birds, Mayr turned to the theoretical problems of distinguishing species. More complex than its modest title implies List of New Guinea Birds (1941) explores the ways closely related species can be distinguished from one another and variations can arise within a species. This work and two field guides for South Pacific birds included bio-geographical work that led him to the idea that natural population groups might provide the proper basis for differentiations. Stephen Jay Gould wrote that Mayr "sharpened his notion of species as fundamental units in nature and deepened his understanding of evolution." Also, he had worked with Rothschild's curators Ernst Hartert and Karl Jordan, pioneers of both a biological species concept and the use of subspecific names reflecting geography.

During the 1930's and 1940's biologists accepted the broad premise of Darwin's theory about evolution—that species change and evolve through a process called natural selection. Mayr realized, along with many taxonomists and other biologists, that reform was needed in the concept of species, for the traditional dependence on morphological difference was misleading. Mayr argued brilliantly for a new synthesis, to wed species concepts more firmly to genetics and to the updated Darwinian theory being produced by population geneticists and evolutionary theorists in many subdisciplines. Neo-Darwinism stresses natural selection of genetic differences within populations as the fundamental cause of evolution, and Mayr's biological species concept reflects the reality of populations in the history of life. His "new systematics" thus defines a species as a genetically interacting group, isolated in reproduction from others.

Biologists embraced the revised concept, for it also made species into a real entity, and not merely an arbitrary grouping. Moreover, the variation seen within species became a biologically important phenomenon. Mayr, more than anyone else, led the promotion of the biological species concept and introduced evolutionary genetics to taxonomists with his highly influential Systematics and the Origin of Species (1942).

This book also argued that in the evolving of new species the crucial step is reproductive (genetical) isolation, by whatever means. Rejecting current alternative theories of rapid speciation by mutation or Lamarckism, Mayr's geographical speciation process depends on the gradual accumulation of small changes under natural selection; the usual causes would be environmental change or geographical barriers establishing local, isolated populations.

The decline of Darwinism within biology that had persisted since the late 1800s was reversed after the 1930s, with natural selection again regarded as a fundamental cause of evolution. By answering the speciation question with ideas from genetics and from ecological studies, Mayr became an important architect and spokesman for the modern synthesis of evolutionary theory. He also was instrumental in the founding of the Society for the Study of Evolution and its journal Evolution, serving as its first editor from 1947 to 1949. His theories about speciation not only found general acceptance but won Mayr great respect as well. E.O. Wilson commented that "He gave taxonomy an evolutionary perspective. He got the show on the road."

Mayr resigned his curatorship in 1953 and moved to Harvard University's Museum of Comparative Zoology; he was director of that museum from 1961 to 1970. In further work on speciation theory he emphasized the founder effect, in which changes start with isolation of a small subpopulation, carrying a limited gene pool and perhaps living in changed environmental circumstances. Mayr's field experience led him to conclude that selection would operate in this way often on the periphery of a species' range, allowing what he termed peripatetic speciation. Presented as a staunchly neo-Darwinian position, especially in his landmark Animal Species and Evolution (1963), this speciation theory does allow rapid change in founder populations and has led some evolutionists, such as Stephen Jay Gould, to argue for a less gradual mode of evolution. Mayr maintained the adequacy of the Modern Synthesis position, as so ably expounded in his 1963 book.

Always interested in a wide range of subjects, Mayr also wrote influentially on the philosophy and history of biology. Summing up and expanding upon his many papers is The Growth of Biological Thought (1982), which presents his historical analysis of ideas about the organization and evolution of life.

Already honored with numerous degrees and medals, Mayr was the recipient in 1984 of the Balzan prize, considered to be the equivalent of the Nobel Prize for the biological sciences. He also holds ten honorary degrees, was elected to the National Academy of Sciences, received the Darwin-Wallace Medal in 1958, the Linnean Medal in 1977, the Gregor Mendel medal in 1980 and the Darwin Medal of the Royal Society in 1987. In 1994, at the age of 90, Mayr was awarded the prestigious Japan Prize by the Committee on the International prize for biology.

In an 1983 interview in Omni, Mayr discussed many of the concerns that he expressed throughout his career "Man must realize that he is part of the ecosystem and that his own survival depends on not destroying that ecosystem". He remained pessimistic about the future of the human race. When Mayr retired from Harvard as professor emeritus of zoology in 1975, Stephen Jay Gould observed that he really only changed careers—from a scientist he became a historian of science. In 1991, at age 87, he published another carefully wrought discussion of evolution One Long Argument in which he stated "the basic theory of evolution has been confirmed so completely that modern biologists consider evolution simply a fac…. Where evolutionists today differ from Darwin is almost entirely on matters of emphasis. While Darwin was fully aware of the probabalistic nature of selection, the modern evolutionist emphasizes this even more. The modern evolutionist realizes how great a role chance plays in evolution."

In 1997, The Science of the Living World was released to great acclaim by the scientific community. In it Mayr managed to condense the complicated history of biological thought. He tried to promote a view of knowledge acquisition called evolutionary epistemology which suggests that human understanding evolves like life itself.

Further Reading

Mayr anthologized his most influential articles, with an autobiographical and explanatory section, in his Evolution and the Diversity of Life (1976). He is also included in the McGraw-Hill Modern Men of Science, vol. II (1968). His own works include List of New Guinea Birds (1941); Systematics and the Origin of the Species (1942); Animal Species and Evolution (1963); The Growth of Biological Thought (1982); One Long Argument (1991); The Science of the Living World (1997). □

Mayr, Ernst

American Biologist and Ornithologist 1904-

Ernst Mayr, one of the cofounders of the "Modern Synthesis" in evolutionary biology (along with Theodosius Dobzhansky, George Gaylord Simpson, and G. Ledyard Stebbins), is a naturalized American citizen born in Kempten, Germany. The Modern Synthesis sought to integrate Charles Darwin's theory of natural selection with the recent development of population genetics by R. A. Fisher, Sewall Wright, and J. B. S. Haldane.

Mayr showed an ardent interest in birds from an early age and took only eighteen months to complete his doctoral program in ornithology at the Berlin Natural History Museum (1926). In 1928 he began leading a series of ornithological expeditions to New Guinea, the Philippines, and the Solomon Islands. His field guides to the birds of these areas continue to be used by scholars of ornithology.

After his Pacific forays, Mayr joined the staff of the American Museum of Natural History (AMNH) in New York City in 1931 and was appointed curator of its ornithology collection in 1932, a position he would hold for over twenty years. During this time, he described twenty-six new bird species and 410 subspecies. In the style of Darwin, his intellectual hero, Mayr used his accumulated knowledge of natural history to gain insight into broad evolutionary questions. His work at AMNH focused on systematics: the classification, genealogy, and defining boundaries of species and populations. Mayr's classic "biological species concept" won wide acceptance among scientists in its time, and continues to structure many scientist's thinking about species: "species are groups of actually (or potentially) interbreeding natural populations which are reproductively isolated from other such groups." This definition has led to the identification of many previously unknown species. Mayr's contribution to systematics is reflected in two seminal works: Systematics and the Origin of Species (1942), where the biological species concept was presented, and Methods and Principles of Systematic Zoology (1953).

Mayr left AMNH in 1953 to become the Alexander Agassiz Professor of Zoology at Harvard's Museum of Comparative Zoology, a position he still holds today as emeritus faculty; in 1961, he was appointed director of the museum. At Harvard, Mayr shifted his intellectual focus from systematics to speciation (how species are formed) and other general questions in evolutionary biology. He published Animal Species and Evolution, a major synthesis of evolutionary theory, in 1963. Mayr has been a leading advocate of population thinking—the notion that species are best understood by taking into account the fact that traits vary among individuals—in the classification and study of living things. According to Mayr, speciation typically occurs as a result of geographic separation, and therefore from a reduction of gene flow, between large parent populations and small founder populations.

Mayr is an eminent scholar in the history of evolutionary biology, and his recent career is marked by two major works on the subject, The Growth of Biological Thought (1982) and One Long Argument: Charles Darwin and the Genesis of Modern Evolutionary Thought (1991).

Mayr's accomplishments have earned him numerous honors, including the National Medal of Science (1970), the U.S. government's highest award for scientific research, and the Royal Swedish Academy of Science's Crafoord Prize (1999).

Gil G. Rosenthal

Bibliography

Mayr, Ernst. Evolution and the Diversity of Life: Selected Essays. Cambridge, MA: Harvard University Press, Belknap Press, 1997.

Ernst Mayr

1904

German-American Evolutionary Biologist

Ernst Mayr was one of the scientists who helped develop the so-called "modern synthesis" of evolutionary theory, combining evolution, genetics, and speciation. He also developed and promoted the widely accepted biological concept of species, which also provided an explanation of how new species evolve.

Mayr was born in Kempten, Germany, on July 5, 1904. The son of a judge, he had a comprehensive early education and took a particular interest in birds. In college, he first studied medicine at the University of Greifswald in Berlin from 1923-26, but became more and more intrigued by zoology, particularly after he met noted ornithologist Erwin Stresemann. Mayr's meeting with Stresemann was prompted by Mayr's 1923 sighting of a bird that had not been seen in Europe for decades. With encouragement from Stresemann, Mayr transferred to the zoology program at the University of Berlin, and earned his doctorate in the field summa cum laude in 1926.

Upon graduation, Mayr remained at the University of Berlin as assistant curator in its zoological museum until 1932. While in that position, Mayr headed three scientific expeditions to New Guinea and the Solomon Islands from 1928-30, and spent much of the remainder of his time identifying and classifying the birds he saw and collected on those trips. His reputation as a skilled ornithologist grew, and he accepted a position as associate curator in 1932, and a promotion to curator in 1934, at the American Museum of Natural History in New York, where he stayed until 1953. During this time, he also became a U.S. citizen. From the museum, Mayr moved on to Harvard University in 1953 as Alexander Agassiz Professor of Zoology and in 1961 also took on the title of director of the Museum of Comparative Zoology. He retired from Harvard in 1975, and now holds the title of professor emeritus from that university.

During his long and accomplished career, Mayr intertwined evolutionary concepts with his studies of animal variation. One of the first major problems he addressed was the definition of a species: When was one organism sufficiently different from another so that they could be termed separate species? With an eye toward the ideas behind evolution, and particularly the role of genetics, he promoted a biological concept of species. Under this definition, two different species cannot interbreed. This reproductive isolation is necessary to prevent gene flow between them. Different species may be reproductively isolated for a number of reasons. For example, the two species may live in different habitats, they may breed at different times of the year, or the males of one species may not exhibit the courtship behaviors that attract females of the other species. Before Mayr's definition, species were delineated in a more subjective manner, such as whether they looked fairly similar.

Following this definition, he also explained how new species could evolve. For example, he explained how a small population of one species could be separated from the main population. Because the small population had a limited gene pool, its successive generations could develop different characteristics. If the offshoot group's characteristics became sufficiently different from the original group so that individuals of the two groups could not reproduce, the offshoot population would, by definition, be a separate species.

Mayr's 1942 book, Systematics and the Origin of Species, further coalesced evolution, genetics, and speciation, and paved the way for the "modern synthesis" of evolutionary theory.

The author of 20 books, Mayr has received a number of prestigious honors, including the Balzan Prize in 1983, the International Prize for Biology in 1994, and the Crafoord Prize for Biology in 1999.

LESLIE A. MERTZ

MAYR, Ernst

MAYR, Ernst. American (born Germany), b. 1904. Genres: Biology, Philosophy. Career: Assistant Curator, Zoological Museum, University of Berlin, 1926-32; Whitney Research Associate in Ornithology, 1931-32, Associate Curator, 1932-44, and Curator, Whitney-Rothschild Collection, 1944- 53, American Museum of Natural History, NYC; Alexander Agassiz Professor of Zoology 1953-75, and Director, Museum of Comparative Zoology, 1961-70, Emeritus Professor, 1975-, Harvard University, Cambridge, MA. Founded Society for the Study of Evolution, 1946; Founding Editor, Evolution, 1947-49. Publications: List of New Guinea Birds, 1941; Systematics and the Origin of Species, 1942; Birds of the Southwest Pacific, 1945; (with J. Delacour) Birds of the Philippines, 1946; (with E.G. Linsley and R.L. Usinger) Methods and Principles of Systematic Zoology, 1953; Animal Species and Evolution, 1963; Principles of Systematic Zoology, 1969; Populations, Species, and Evolution, 1970; Evolution and the Diversity of Life, 1976; (with W.B. Provine) The Evolutionary Symbiosis, 1980; The Growth of Biological Thought, 1982; Towards a New Philosophy of Biology, 1988; One Long Argument, 1991; This Is Biology, 1997; What Evolution Is, 2001; (with J. Diamond) The Birds of Northern Melanesia, 2001. Address: 207 Badger Ter, Bedford, MA 01730-1286, U.S.A.