Ernst Walter Mayr (July 5, 1904, Kempten, Germany – February 3, 2005, Bedford, Massachusetts U.S.) was one of the twentieth century's leading evolutionary biologists. He was also a renowned taxonomist, tropical explorer, ornithologist, historian of science, and naturalist. His work contributed to the conceptual revolution that led to the modern evolutionary synthesis of Mendelian genetics, systematics, and Darwinian evolution, and to the development of the biological species concept.
Mayr's theories on speciation remain the leading view of how new species evolve from common ancestors via Darwinian principles, and he provided the theoretical underpinning for the theory of punctuated equilibrium. Apart from biology, his prolific writings include influential works on the philosophy and history of science, and of biology in particular.
Mayr authored over 20 books and published more than 700 scientific papers.
Mayr was an atheist, stating that "there is nothing that supports the idea of a personal God" (Shermer and Sulloway 2000). At the same time, however, he noted that "famous evolutionists such as Dobzhansky were firm believers in a personal God. He would work as a scientist all week and then on Sunday get down on his knees and pray to God." Sometimes there is an assumption of an either-or dichotomy at work between evolutionary theory and religious faith: Either evolution is true or God exists. In reality, however, these two positions are often successful juxtaposed. Of course, the extreme dogmatic positions on the two sides are exclusionary, with the religious concept of young earth creationism unable to reconcile with the long-time periods evident in descent with modification, and the equally dogmatic adherence of some evolutionists to philosophical materialism (that matter is the ground of all existence and spirit either does not exist or is a product of matter) unable to reconcile with belief in God. Yet, there are a wide variety of religious viewpoints that do allow evolutionary change, including those that accept the pattern of evolution (descent with modification) but not the process of natural selection, and those that accept both the pattern and the process.
Mayr was born in Kempten, Germany in 1904 and completed his high school education in Dresden. He planned to become a physician and undertook pre-clinical studies. However, he also was attracted to ornithology, the study of birds. Hull (1988) states that "officially he was enrolled as a medical student, but his true love was ornithology." Mayr was introduced to Erwin Stresemann, a well-known ornithologist at Berlin's Zoological Museum, as a result of Mayr's claimed sighting of red-crested pochards in Germany—a species that had not been seen in Europe for 77 years. After a tough interrogation, Stresemann accepted and published the sighting as authentic. Stresemann offered him a position with the Berlin Museum and the prospect of bird-collecting trips to the tropics on the condition that he completed his PhD studies in 16 months. Mayr completed his PhD in ornithology at the University of Berlin in June 1926 at the age of 21, while also completing (in 1925) his pre-clinical studies at medical school (Diamond 2001). Mayr then accepted the position offered to him at the Museum.
At the International Zoological Congress at Budapest in 1927, Mayr was introduced by Stresemann to banker and naturalist Walter Rothschild (Lord Rothschild's Museum), who asked him to undertake an expedition to New Guinea on behalf of himself and the American Museum of Natural History in New York. There was a desire to "clean up" the outstanding ornithological mysteries of New Guinea, by tracking all of the birds of paradise known only from specimens collected by natives and not yet traced to their home ground (Diamond 2001). In New Guinea, Mayr collected several thousands bird skins (he named 26 new bird species during his lifetime) and, in the process also named 38 new orchid species. Mayr did thorough bird surveys of New Guinea's five most important north coastal mountains. In the process, he was officially reported to have been killed by local tribes; survived severe cases of malaria, dengue, dysentery, and other diseases; and had a forced descent down a waterfall and nearly drowned in an overturned canoe (Diamond 2001). Nonetheless, he succeeded in his mission by reaching the summits of all five mountains and amassing large collections (Diamond 2001). None of the findings were the mysterious missing birds of paradise, leading Stresemann to conclude later that they were thus hybrids between known species (Diamond 2001).
During his stay in New Guinea, Mayr was invited to accompany the Whitney South Seas Expedition to the Solomon Islands. With this expedition, Mayr participated in surveys of birds in several islands in the Pacific.
Mayr received a telegram in 1930 to return to the American Museum of Natural History to identify the tens of thousands of birds specimens collected by the Whitney Expedition (Diamond 2001). In 1931, he accepted a curatorial position at the American Museum of Natural History, where he played the important role of brokering and acquiring the Walter Rothschild collection of bird skins, which was being sold in order to pay off a blackmailer, an unknown woman.
Mayr married Margarete Simon in 1935, and had two daughters with her. (She passed away in 1990.)
During his time at the museum, Mayr produced numerous publications on bird taxonomy, and in 1942, he published his first book, Systematics and the Origin of Species, a text that was renowned for completing the modern evolutionary synthesis.
After Mayr was appointed as curator at the American Museum of Natural History, he influenced American ornithological research by cultivating mentoring relationships with young birdwatchers. Mayr organized a monthly seminar under the auspices of the Linnaean Society of New York. This society, under the influence of J. A. Allen, Frank Chapman, and Jonathan Dwight concentrated on taxonomy and later became a clearing house for bird banding and sight records. There were a group of eight young birdwatchers from the Bronx and later became the Bronx County Bird Club, being led by Ludlow Griscom. Mayr was surprised at the differences between American and German Birding Societies. He noted that the German society was more scientific and concerned with life histories and reports on recent literature. Mayr also encouraged his Linnaean Society seminar participants to take up a specific research project of their own. One of Mayr's seminar participants was Joseph Hickey and under Mayr's influence went on to write A Guide to Birdwatching (1943). Hickey remembered later: "Mayr was our age and invited on all our field trips. The heckling of this German foreigner was tremendous, but he gave tit for tat, and any modern picture of Dr E. Mayr as a very formal person does not square with my memory of the 1930s. He held his own." Mayr's said of his own involvement with the local birdwatchers: "In those early years in New York when I was a stranger in a big city, it was the companionship and later friendship which I was offered in the Linnaean Society that was the most important thing in my life."
Another person that Mayr greatly influenced was Margaret Morse Nice. Mayr encouraged her to correspond with the European ornithologists of the time, and helped her in her landmark study on Song Sparrows.
Mayr joined the faculty of Harvard University in 1953, where he also served as director of the Museum of Comparative Zoology from 1961 to 1970. He retired in 1975 as professor of zoology, showered with honors. He continued, however, for many years on the staff of the museum as professor emeritus.
Following his retirement, Mary went on to publish more than 200 articles, in a variety of journals—more than some reputable scientists publish in their entire careers. Indeed, 14 of his 25 books were published after he was 65. Mayr was 97 years old when he published What Evolution is, and even as a centenarian, he continued to write books. On his 100th birthday, he was interviewed by Scientific American magazine.
Mayr received innumerable awards during his career, including the National Medal of Science, the Balzan Prize, the Sarton Medal of the History of Science Society, and the International Prize for Biology. In 1939, he was elected a Corresponding Member of the Royal Australasian Ornithologists Union. He was never awarded a Nobel Prize, but he noted that there is no Prize for evolutionary biology, and that Darwin would not have received one, either. Mayr did win a 1999 Crafoord Prize. That prize honors basic research in fields that do not qualify for Nobel Prizes and is administered by the same organization as the Nobel Prize.
Mayr was co-author of six global reviews of bird species new to science (listed below).
As a traditionally trained biologist with little mathematical experience, Mayr was often highly critical of early mathematical approaches to evolution, such as those of J. B. S. Haldane, famously calling in 1959 such approaches "bean bag genetics." He maintained that factors such as reproductive isolation had to be taken into account. In a similar fashion, Mayr was also quite critical of molecular evolutionary studies such as those of Carl Woese. He dismissed Richard Goldschmidt's mechanism for speciation as speciation by means of "hopeful monsters," an epithet that caught on (Hull 1988).
In many of his writings, Mayr rejected reductionism in evolutionary biology, arguing that evolutionary pressures act on the whole organism, not on single genes, and that genes can have different effects depending on the other genes present. He advocated a study of the whole genome rather than of isolated genes only. He also agreed with Dobzhansky that speciation is a populational affair (Hull 1988).
Mayr was an outspoken defender of the scientific method, and one known to sharply critique science on the edge. As a notable recent example, he criticized the search for aliens as conducted by fellow Harvard professor Paul Horowitz as being a waste of university and student resources, for its inability to address and answer a scientific question.
Hull noted in 1988 that "Mayr was—and still is—an outgoing man who is very much at home at professional meetings and conferences, where he vigorously and tirelessly defends his views. He makes no distinctions between august experts and hesitant graduate students. He is as willing to spend time setting one straight as the other."
Between 1937 and 1947, neo-Darwinism or the modern evolutionary synthesis integrated Charles Darwin's theory of evolution by natural selection, Gregor Mendel's theory of genetics as the basis for biological inheritance, and mathematical population genetics. This was one of the most significant, overall developments in evolutionary biology since the time of Darwin. Bowler (1988) stated that there is "a sense in which the emergence of the modern synthetic theory can be seen as the first real triumph of Darwinism."
Essentially, neo-Darwinism introduced the connection between two important discoveries: the units of evolution (genes) with the mechanism of evolution (natural selection). By melding classical Darwinism with the rediscovered Mendelian genetics, Darwin's ideas were recast in terms of changes in allele frequencies. Neo-Darwinism thus fused two very different and formerly divided research traditions, the Darwinian naturalists and the experimental geneticists.
Mayr's 1942 work, Systematics and the Origin of Species, was one of the four canonical works of the modern evolutionary synthesis, joining those of G. G. Simpson Tempo and Mode in Evolution, G. Ledyard Stebbins Variation and Evolution in Plants, and Theodosius Dobzhansky Genetics and the Origin of Species. Mayr himself places the key dates for the development of the synthesis between 1937, with Dobzhansky's work, and an international symposium at Princeton, New Jersey, January 2-4, 1947, which marked the formal completion of the synthesis (Hull 1988; Mayr 1982). The modern synthesis remains the prevailing paradigm of evolutionary biology.
Hull (1988) claimed that Mayr wrote his work "in white-hot indignation," in response to Richard Goldschmidt's The Material Basis of Evolution (1940).
Charles Darwin's famous book "The Origin of Species" presented a theory for how species evolve and change over time. Although Darwin did not provide details on how a new species arises, he viewed speciation as a gradual process. If Darwin was correct, then when new incipient species are forming there must be a period of time when they are not yet distinct enough to be recognized as species. Darwin's theory suggested that there was often not going to be an objective fact of the matter, on whether there were one or two species.
Darwin's book triggered a crisis of uncertainty for some biologists over the objectivity of species, and some came to wonder whether individual species could be objectively real—i.e., have an existence that is independent of the observer (Johnson 1908; Bailey 1896).
While neither Darwin nor anyone else in his time knew a definitive answer to the "species problem"—how multiple species could evolve from a single common ancestor—Ernst Mayr approached the problem with a new definition for the concept "species'." Ernst Mayr's 1942 book, Systematics and the Origin of Species, was a turning point for the species problem. In it he wrote about how different investigators approach species identification, and he characterized these different approaches as different species concepts. He wrote that a species is not just a group of morphologically similar individuals, but a group that can breed only among themselves, excluding all others. When populations of organisms get isolated, the sub-populations will start to differ by genetic drift and natural selection over a period of time, and thereby evolve into new species. He also developed the idea that most significant and rapid genetic reorganization occurs in extremely small populations that have been isolated, the "Founder Principle."
Mayr perspective on what constitutes a species came to be called the Biological Species Concept (BSC), which is that a species consists of populations of organisms that can reproduce with one another and that are reproductively isolated from other such populations. Mayr was not the first to define "species" on the basis of reproductive compatibility. Many others before Mayr had suggested this idea, as Mayr (1982) makes clear in his book on the history of biology. For example, Mayr discusses how Buffon proposed this kind of definition of "species" in 1753. The idea of shared reproduction within species is even contained in the Biblical myth of Noah's ark, in which each species was preserved by saving a reproductive pair.
Theodosius Dobzhansky was a close contemporary of Mayr's and the author of a classic book, that came out a few years before Mayr's, that was about the evolutionary origins of reproductive barriers between species (Dobzhansky 1937). Many biologists credit Dobzhansky and Mayr jointly for emphasizing the need to consider reproductive isolation when studying species and speciation (Mallet 2001; Coyne 1994).
After articulating the biological species concept in 1942, Mayr played a central role in the species problem debate over what was the best species concept. After Mayr's 1942 book, many more species concepts were introduced. Some, such as the Phylogenetic Species Concept (PSC), where designed to be more useful than the BSC for actually deciding when a new species should be described. However, not all of the new species concepts were about identifying species, and some concepts were mostly conceptual or philosophical.
Mary staunchly defended the biological species concept against the many definitions of "species" that others proposed. Mayr was persuasive in many respects and from 1942 until his death in 2005, he and the biological species concept (BSC) played a central role in nearly all debates on the species problem. For many, the Biological Species Concept was a useful theoretical idea because it leads to a focus on the evolutionary origins of barriers to reproduction between species. But the BSC has been criticized for not being very useful, because it is not very much for deciding when to identify new species. It is also true that there are many cases where members of different species will hybridize and produce fertile offspring when they are under confined conditions, such as in zoos. One fairly extreme example is that lions and tigers will hybridize in captivity, and at least some of the offspring have been reported to be fertile. Mayr's response to cases like these is that the reproductive barriers that are important for species are the ones that occur in the wild. But even so it is also the case that there are many cases of different species that are known to hybridize and produce fertile offspring in nature.
His theory of peripatric speciation (a more precise form of allopatric speciation which he advanced) based on his work on birds, is still considered a leading mode of speciation and was the theoretical underpinning for the theory of punctuated equilibrium.
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