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 fact... 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. Also in 1997, Mayr's This is Biology was published.

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).