Open access, freely available online Obituary On the Importance of Being Ernst Mayr “Darwin’s apostle” died at the age of 100 Axel Meyer orn on July 5, 1904, in Kempten in southern Germany, Ernst BMayr passed away peacefully at the Methuselah-like age of 100 on February 3, 2005, in Bedford near Cambridge, Massachusetts. Mayr was, by the accounts of his Harvard colleagues the late Stephen Jay Gould and Edward O. Wilson, not only the greatest evolutionary biologist of the 20th century, but even its greatest biologist overall. Thomas Henry Huxley was dubbed “Darwin’s bulldog” for fi ghting for the acceptance of Darwinian ideas soon after their inception in the last decades of the 19th century. Similarly, Ernst Mayr has been called “Darwin’s apostle” or the “Darwin of the 20th century” for promoting and dispersing Darwin’s hypotheses throughout the past century. Mayr lived for a century and DOI: 10.1371/journal.pbio.0030152.g001 accomplished more than several Ernst Mayr in 1994, after receiving an honorary degree at the University of Konstanz lifetime’s worth of science in different (Photo: University of Konstanz) biological disciplines. Brought up by parents who loved nature and who took then, like many of his contemporaries, In the 1930s, Mayr’s friendship the young Ernst on long hikes, he was in Lamarkian inheritance. Sent by his and interactions with the Russian- exposed to natural history early on, advisor Erwin Stresemann from Berlin born Columbia University population but although birds were his passion and fi nanced by Lord Rothschild, he geneticist Theodosius Dobzhansky, all his life, he was, like Darwin, fi rst had just returned from over two years author of the landmark text Genetics compelled to study medicine. He began of perilous fi eldwork in New Guinea and the Origin of Species published in his studies at Greifswald—a prime and the Solomon Islands. The parallels 1937 [2], started to infl uence his birding spot—and through the chance to the lives of Darwin and Wallace thinking. Mayr’s interests subsequently observation of a rare species of duck may not be coincidental. During these began to diversify beyond taxonomy that had not been seen in Germany for expeditions, forlorn, at times given up into evolutionary biology, and this many years, he came in contact with the for dead, exposed to tropical diseases expansion of his interests culminated Berlin ornithologist Erwin Stresemann, and the danger of headhunters, he in his fi rst, and possibly still most who proposed that he switch to biology. collected the skins of thousands of important book, Systematics and the Mayr abandoned medicine for biology specimens, eating the fl esh of many. Origin of Species, published in 1942 and published his fi rst scientifi c paper Mayr was not only the ornithologist [3]. This was his main contribution to (of a total of almost 700) at the age of who probably tasted the largest number the so-called Modern Synthesis of the 19 in 1923, receiving his Ph.D. from of different species of birds, but he also Humboldt University in Berlin after named 26 new species and over 400 only 16 months of graduate work and new subspecies, more than any other Citation: Meyer A (2005) On the importance of being dissertation research; he was just 22. taxonomist. In over 300 publications Ernst Mayr. PLoS Biol 3(5): e152. Ernst Mayr’s last book (of a total of 25) throughout his life, he discussed and Copyright: © 2005 Axel Meyer. This is an open-access was published in August 2004, a month described the geographic variation and article distributed under the terms of the Creative Commons Attribution License, which permits after he turned 100 [1]. distribution of birds and he also edited unrestricted use, distribution, and reproduction in In 1931, thinking that he would the last eight volumes of the Checklist any medium, provided the original work is properly cited. not be offered a permanent post in of the Birds of the World. His main Germany, he moved from Berlin to the occupation during his 20 years at the Axel Meyer is Professor of Zoology and Evolutionary American Museum of Natural History American Museum was to curate and Biology at the University of Konstanz in Germany. E-mail: [email protected] in Manhattan. In New York he called research the 280 000 specimens of the himself an ornithologist, and believed Rothschild collection. DOI: 10.1371/journal.pbio.0030152 PLoS Biology | www.plosbiology.org 0750 May 2005 | Volume 3 | Issue 5 | e152 1930s and 1940s, a scientifi c sea change species arise, since the criterion of proposed by Nils Eldredge and Gould that came about largely through the reproductive isolation provided a in 1972 [7]. They noted that long contributions of Mayr and Dobzhansky scientifi cally rigorous litmus test. periods of morphological stasis were and other scientists such as Ronald The origin of species is a topic to sometimes interrupted (punctuated) A. Fisher and George G. Simpson. which Darwin himself, in spite of the by short periods of drastic phenotypic Mayr’s fi rst book combined insights promising title of his famous book, change in the fossil record. Somewhat and methods from paleontology, did not say all that much. Mayr’s ironically, Mayr, who considered population genetics, systematics, and understanding of the biogeographic himself a “gradualist” all his life, seems natural history, thus providing a unifi ed distributions of bird species, to have also provided a mechanism for modern evolutionary theory. Patterns overlaid with extensive knowledge variability in rates of evolution along and processes in natural populations about variation in morphology, evolutionary lineages. would now be seen as consistent led him to develop concepts about After establishing the Society for with Darwinian natural selection the geographic mechanisms of the Study of Evolution and serving as and Mendelian mechanisms of speciation—cornerstones for those the fi rst editor of its journal, Evolution, inheritance, and the behavior of genes studying speciation today. The Mayr moved to Harvard University in in populations came to be understood geographic separation of populations, 1953 as the Alexander Agassiz Professor through laboratory population such as by rivers or valleys, he argued, of Zoology and curator of birds at the genetic experiments and theoretical prohibits homogenizing gene fl ow Museum of Comparative Zoology. By mathematical predictions. Mayr was the between them. If such isolated this time, one surely would have labeled last survivor, and historical eyewitness, (termed allopatric) populations him primarily an evolutionary biologist among the architects of the Modern accumulate mutations over time, this rather than an ornithologist. His Synthesis. might lead to the divergence of such interests expanded even further into Ernst Mayr had many fundamental populations from each other, and the theory of systematics—another fi eld insights into evolutionary biology, reproductive isolation might arise as to which he made many contributions and almost every topic of importance a simple byproduct of these separate (see Principles of Systematic Zoology [8]). in evolution was advanced by his evolutionary histories. Mayr staunchly A lifelong and, it seems fair to say, futile ideas. Perhaps his most widely known defended this idea during sometimes fi ght with the then emerging idea of contribution is to the current notion heated debates and further developed cladistics in systematic biology began. of what constitutes a species. Darwin it and other hypotheses regarding Ernst Mayr also served as director of did not think that species were geographic mechanisms of speciation the Museum of Comparative Zoology real in the philosophical sense, but over many decades (outlined in depth before his retirement in 1975 and rather that they were the result of in the 797 pages of Animal Species and oversaw the building of a new addition the human predilection to perceive Evolution [4]). to the museum, whose library was discontinuity among continuously One mechanism of speciation in renamed after him ten years ago. varying individuals. Most biologists particular is still contested (see [5] What of his retirement? Mayr nowadays disagree with Darwin’s view and [6]). Mayr called it “peripatric published 14 of his 25 books in of species, largely because of Mayr’s speciation” or “founder-effect the 30 years that followed after his “biological species concept”. Together speciation.” And it is an idea that offi cial retirement. During the last with Dobzhansky, Mayr developed Ernst Mayr was particularly fond two decades of his life, Mayr began this defi nition of species “as groups of of. He believed it to be his most to think and write more about the interbreeding populations in nature, important contribution to evolutionary history and philosophy of biology. His unable to exchange genes with other biology. This model was again most important work of this period such groups living in the same area” inspired by Mayr’s own natural history was The Growth of Biological Thought [2,3]. Barriers to gene fl ow between observations. He noted that on some [9], a monumental 974 pages. Here, species—termed reproductive isolating New Guinea islands, populations and in later books and publications mechanisms—keep biological species of birds differed markedly from (he also founded the Journal of the distinct through processes such as individuals of the mainland population. History of Biology), he laid out why he species-specifi c mate choice and hybrid He reasoned that this differentiation thought that the philosophy of biology sterility. Although there are theoretical and speciation could result from a is an autonomous science that differs and operational problems with the small number of individuals founding fundamentally from the philosophy biological species concept (e.g., it does the island population. By bringing of science, which, Mayr implied, was not apply to asexually reproducing only a subset of all the genes of the largely derived from physics.