Ernst Mayr, 100; Biologist Explained Species Shifts in Darwin’s Theory of Evolution

Ernst Mayr, the Harvard biologist who took the sweeping evolutionary claims of Charles Darwin and showed how the complex process actually works, died Thursday at a retirement community in Bedford, Mass., after a short illness. He was 100.

Mayr created the first working definition of what a species is and showed how genetics and population movements combined to create new species, an intellectual process known as evolutionary synthesis, which biologist Stephen Jay Gould of Harvard termed “one of the half-dozen major scientific achievements of our century.”

He was also a pioneer in studying the history and philosophy of biology, working tirelessly throughout his life to promote that long-disrespected science to an equal footing with the hard sciences of physics, chemistry and astronomy.

“He’s the Darwin of the 20th century, the defender of the faith,” said science historian Vassiliki Betty Smocovitis of the University of Florida in Gainesville.

Even the Biblical creationists, who fought with him throughout his career, recognized his importance, calling him “the unquestioned dean of the modern evolutionary establishment.”

In biology, said F. Clark Howell of UC Berkeley, “everybody stands in some way in his shadow.”

Mayr’s ideas trace back to Darwin’s 1859 publication, “On the Origin of Species,” which established the concept of natural selection -- better known as survival of the fittest.

In contrast to the Biblical theory that all species on the planet were created in their current form by an almighty power, Darwin reasoned that all creatures were continually developing minor changes that made them either more or less fit to survive in their ecological niches. Those with good changes survived, while those with less propitious ones were weeded out.

Over long periods of time, he theorized, those small changes accumulated until entirely new species were established.

Although Darwin’s conclusion was widely accepted, the question of how those small changes occurred was hotly debated. Many researchers thought that the process of accumulated changes in individual genes required far too much time to occur to account for the great variety of species now present.

They argued that the creation of new species must come from a simultaneous, wholesale genetic mutation, or “systemic mutation,” that led to the instantaneous emergence of “hopeful monsters” sharply different from their parents. Those “monsters” that had adaptive characteristics survived and became new species. Those that did not withered away.

The leading proponent of this idea was geneticist Richard Goldschmidt. In 1939, while Mayr was working at the American Museum of Natural History in New York City, he traveled to Yale to attend a lecture by Goldschmidt.

What he heard so offended him that he vowed, in his own words, to “eliminate” those ideas “from the panorama of evolutionary controversies.”

The series of books, articles and speeches that flowed from that vow, along with the related work of the late Theodosius Dobzhansky and George Gaylord Simpson, did just that, establishing a core of understanding on the topic that has survived for more than half a century. Mayr concluded that the driving force for natural selection was the geographic isolation of small populations.

The foundation for his work was laid two decades earlier on a series of collecting expeditions to New Guinea and the Solomon Islands, in which the newly minted PhD cataloged the majority of the region’s birds. Mayr was often the first white man to have visited many of the regions, enduring hostility, dengue fever, malaria, dysentery and loneliness.

Mayr would shoot the birds and record all their characteristics. Then he would eat them. In his later years, he often joked that he held the world record for the number of birds of paradise consumed. He noted that all the species tasted pretty much the same. The only ones he didn’t like were cormorants, which were “too fishy.”

While cataloging his prizes, he became acutely aware that the existing methods of determining species identifications were woefully inadequate. Two major schools of thought then prevailed. One school, founded by the Swedish botanist Carolus Linnaeus, judged species identity simply by physical appearance.

A more modern school of thought turned to genetics for defining species. But both had their shortcomings. Linnaeans, for example, considered the snow goose and the blue goose of the northern United States separate species because they looked so different. But later workers determined that they are simply color variations of the same bird.

At the opposite extreme, virtually all organisms -- even within the same species -- are slightly different genetically, so geneticists were identifying more species than could be justified.

Mayr offered a more practical definition, concluding that species are groups of animals that can interbreed and produce offspring. Blue geese and snow geese can mate and produce offspring; hence they are the same species. For the first time, biologists had an objective and logical way to distinguish among species.

During his collecting expeditions, Mayr also observed that individual species of birds tended to occur in small geographic pockets physically separated from closely related -- but nonetheless different -- species. Darwin had noticed the same thing in the Galapagos, but didn’t follow the observation to its logical conclusion.

In his landmark 1942 publication, “Systematics and the Origin of Species,” Mayr concluded that it was geographic isolation that led to the formation of new species.

In Australia, for example, climate changes caused the vast forest that once covered the continent to slowly break up into smaller woodlands. The growing deserts between the forests made it difficult or impossible for isolated populations of birds to interbreed.

With a limited gene pool within each forest, small genetic mutations accumulated more rapidly, leading to the development of new populations that were better suited to their new environment. Eventually, these groups became new species, incapable of mating with other descendants of their original ancestors.

In varying degrees, he concluded, the same process was responsible for all natural selection.

His conclusions were quickly accepted. As Mayr later wrote, “That geographic speciation is the prevailing process of speciation ... was no longer questioned after this date.”

Mayr was always somewhat disappointed that he did not receive a Nobel Prize for his work. Such an award was, in fact, impossible, because biology is not one of the prize categories. As Mayr wryly noted, “Darwin wouldn’t have won it, either.”

But he did score a trifecta in becoming the first scientist to win all three of the major prizes in biology: the Balzan Prize in 1983, the International Prize for Biology in 1994, and the Crafoord Prize in 1999. He donated most of the hundreds of thousands of dollars he received from the awards to Harvard’s Museum of Comparative Zoology, the Nature Conservancy and other organizations.

“The money is the least important part of the prize,” he said upon winning the Balzan Prize.

Ernst Walter Mayr was born July 5, 1904, in the Bavarian city of Kempten, near the borders of Austria and Switzerland. His father was a judge, but the family line included a large number of physicians, and he enrolled in the medical school at the University of Greifswald.

His father had been an avid bird-watcher, and young Ernst followed in his footsteps. By the age of 10, he could identify all the local species by their calls.

The lure of nature and travel called him away from what he perceived as the pedestrian life of medicine. “I was curious about far places,” he told the Harvard Alumni Bulletin, “and decided that, as an M.D., I should have but small chance of traveling.”

With the promise of sponsorship from Lord Lionel Walter Rothschild for a collecting expedition to the South Pacific, Mayr broke off his medical studies and completed his doctorate in biology at the University of Berlin in just 16 months.

After his first two expeditions, he was ready to return home, but the American Museum of Natural History needed a quick replacement for a trip to the Solomon Islands, and he signed on.

The successful expedition led to a job at the museum, which he held until he was recruited by Harvard in 1953.

He remained affiliated with that school for the rest of his life, although in his later years, he spent winters in the more accommodating climate of Rollins College in Winter Park, Fla.

He was productive throughout his life, completing five books in his 90s. Overall, he wrote more than 660 scientific papers and 20 books.

His wife of 55 years, Margarete, died in 1990. Mayr told friends at the time that his life was over, but he recovered and continued his work for another 14 years.

He is survived by two daughters, Christa Menzel of Simsbury, Conn., and Susanne Harrison of Bedford; five grandchildren; and 10 great-grandchildren.