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"In 1859 Darwin published his theory of common descent through natural selection. I don't think there has ever been a set of theories so heavily attacked or that has had so many alternative theories to face. Look at it now. It stands there, not a dent in it," said Ernst Mayr, (then) Alexander Agassiz Professor of Zoology, Emeritus at Harvard University in 1994. What he didn't say, but didn't need to, to anybody followed a century-long natural selection vs genetics debate all through 20th century, was the seminal role he played to ensure Charles Darwin's work survived unscathed.
Mayr, who significantly contributed to the conceptual revolution that led to the modern evolutionary synthesis of Mendelian genetics and Darwinian evolution, passed away on February 3, 2005, in Bedford, Massachusetts, a few months after he turned 100.
Another major contribution in evolutionary biology by Mayr was to champion of a different form of species formation, allopatric speciation. In his classic 1942 book-- Systematics and the Origin of Species --he proposed that when subpopulations of a species become isolated geographically (because of habitat fragmentation or migration), they diverge evolutionarily over many generations. Evolutionary geneticists, on the other hand, championed saltational speciation: rapid evolution of a new species emerges from a small population partially or totally isolated from the parent popuation due to genetic drift.
Mayr argued 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 was the one of the first to advocate the whole genome, rather than isolated genes, should be studied. He spoofed evolutionary geneticists' attempts to use mathematics to treat individual genes in isolation as "beanbag genetics". Swimming against one of the most powerful currents in modern biology, much of which now deals with molecules rather than organisms, he rejected reductionism wholesale.
Ernst Walter Mayr was born in Bavaria (Germany) in 1904. An avid nature-watcher right from childhood, the family tradition prompted him to go for medical studies. A meeting with the famous German ornithologist Erwin Stresemann, a curator of birds at University of Berlin Museum of Natural History, made him turn to zoology. Under Stresemann's supervision, Mayr earned his phd at a young age of 21 and joined the museum as his assistant. Subsequently, he went on expeditions to New Guinea and Solomon Islands, before taking up a position at the American Museum of Natural History, in New York.
His work here in the 1930s and 1940s established him as a central figure in the neo-Darwinist evolutionary synthesis, a resurgence of evolutionary biology and widely regarded as one of the most important scientific developments of the 20th century. Almost single-handedly, he made the origin of species diversity the central question of evolutionary biology. He also pioneered the currently accepted definition of a biological species: an interbreeding population that cannot breed with other groups. "Evolutionary biology in its first 90 years (1859 to the 1940s) consisted of two widely divergent fields: evolutionary change in populations and biodiversity, the domains of geneticists and naturalists, respectively. Its histories were usually written by geneticists, who often neglected the evolution of biodiversity. As I am a naturalist, I consider this neglect a grave deficiency," Mayr wrote in an essay that marked his 100th birthday.
The philosophy of science at that time was totally dominated by essentialism, entirely unsuitable as a foundation for theories dealing with biological populations. More importantly, the paradigm of Darwinian evolution was not a single theory, as Darwin always insisted, but actually composed of five quite independent theories. Two of these were readily accepted by Darwinians: evolution itself and the branching theory of common descent. The other three -- gradual evolution, the multiplication of species, and natural selection -- were accepted by only a minority of Darwin's followers. Indeed, these three theories were not universally accepted until the so-called Evolutionary Synthesis of the 1940s.
Mayr left the natural history museum in 1953 to become Alexander Agassiz Professor of Zoology at the Harvard University Museum of Comparative Zoology. He stayed at Harvard for the rest of his life, becoming Professor Emeritus in 1975. His many honours include the Japan Prize, the Balzan Prize and the Crafoord Prize, perhaps the most prestigious international award for biologists. His achievements include the description of 26 species and 473 subspecies of birds previously unknown to science, and 25 books, the last of which (What Makes Biology Unique) he completed in time for his centenary. Mayr will also be remembered for valiantly fighting to ensure biology's place as a "true science".