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.
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