Ernst Mayr

OBITUARY

Obituary

Feb 10th 2005
From The Economist print edition

Ernst Mayr, evolutionary biologist, died on February 3rd, aged 100

CHARLES DARWIN'S most famous book is called “On the Origin of Species by Means of Natural Selection”. That is not, however, what it is actually about. Natural selection is there in abundance. Darwin shows how small, heritable variations that improve survival and reproduction will accumulate over the millennia. He also shows that groups of similar species have descended from common ancestors. But on the origin of those species—exactly how one ancestral species divides into many—the book is largely silent.

Darwin did not know the answer to this question, and nor did anyone else until Ernst Mayr, a biologist working at the American Museum of Natural History in New York, enlightened them.

First, in 1942, he published “Systematics and the Origin of Species”. This got to the heart of the problem by defining what a species actually is—not a group of individuals that look alike, but a group that can breed among themselves but not with others. That now-routine observation cleared the way to ask how such “reproductive isolation” comes about. Mr Mayr's answer was that bits of large interbreeding populations sometimes get isolated from the main (climate change may break up a range, for example). Natural selection will then do its work on the isolated sub-populations. To the extent that these sub-groups throw up different genetic mutations for selection to work on, and are subjected to different selective pressures, they will evolve in different directions. Eventually, they will become new species.

No doubt, many biologists reacted to this idea in the way that Thomas Henry Huxley reacted to Darwin's when he first heard it: “How extremely stupid not to have thought of that.” But it was Mr Mayr who did the thinking, and thus solved what Darwin and his contemporaries referred to as “the species problem”—in other words, why life on Earth is so diverse. By doing so, he joined a select group of biologists who, in the mid-20th century, rescued Darwin's idea from obfuscation and misunderstanding. Huxley was known as “Darwin's bulldog” for his sturdy public defence of his reclusive friend's ideas. These biologists—Mr Mayr, Theodosius Dobzhansky and George Gaylord Simpson in particular—deserve, perhaps, to be known as Darwin's retrievers.

The neoDars

It was not that biologists had given up on evolution by the 1940s—quite the contrary. But they had got very confused about its mechanism. Darwin himself started the confusion in later editions of “On the Origin”, by retreating from natural selection as the sole mechanism of evolution, and even tinkering with the idea of the inheritance of acquired characteristics.

The geneticists of the early 20th century did not help. They rediscovered the laws of inheritance first developed 40 years earlier by Gregor Mendel, an unsung Moravian monk. They also discovered the idea of genetic mutation. But instead of linking these things to natural selection, they came up with the idea of “saltation”—in other words, sudden mutational shifts from one well-adapted species to another. Nor, the geneticists complained, had there been enough time for natural selection to do its work, given what they had discovered about the rate at which mutations occur, and the fact that most mutations are deleterious. It was all a bit of a mess.

Darwin's retrievers cut through this muddle. Dobzhansky integrated genetics into what became known as the neoDarwinian synthesis with his work on fruit flies. Simpson provided the palaeontology with a classic study of the evolution of horses. Mr Mayr's contribution was to tackle the question of speciation head-on and solve it. (The question of time was disposed of by physicists, who gave radioactive dating to the world, and thus showed it is billions of years old, and also donated nuclear fusion, which has kept the sun shining for those billions of years.)

Mr Mayr's advantage over the laboratory-bound biologists who had hijacked and diluted Darwin's legacy was that, like Darwin, he was a naturalist—and a good one. He identified 26 new species of bird, more than anyone else now alive, and 38 species of orchid. He was born in Bavaria and studied medicine, but found he preferred birdwatching. He arrived in America by a circuitous route that took in New Guinea, the Solomon Islands and Tring, a small town in southern England where Lord Rothschild, a rich naturalist, had established a private museum. He moved to New York when his patron had to sell his collection of bird specimens to the American Museum in order to pay off a blackmailer. Mr Mayr, who helped to broker the deal, relocated with the collection.

Mr Mayr did well in America, ending up in the Alexander Agassiz chair of zoology at Harvard, showered with honours, and proving the fitness of his own genes by living for more than a century. It is an irony, though, that his adopted country is the one place in the developed world where the neoDarwinian explanations that he and his colleagues created are not the commonplace of the schoolbooks, and where many people prefer to cling to the campfire tales of Genesis, rather than face the awesome thesis that Mr Mayr helped to elucidate.

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