Tuesday, February 15, 2005

It's the detail about eating birds of paradise

that's really memorable in this NYT obituary of Ernst Mayr:

Dr. Mayr went on to fulfill what he called ''the greatest ambition of my youth,'' heading off to the tropics. In the South Pacific, principally New Guinea and the Solomon Islands, Dr. Mayr collected more than 3,000 birds from 1928 to 1930. (He had to live off the land, and every bird, after being skinned for study, went into the pot. As a result, he is said to have eaten more birds of paradise than any other modern biologist.)

The South Seas experience, he once said, ''had an impact on my thinking that cannot be exaggerated.'' For it was his detailed observations of the differences among geographically isolated populations that contributed to his conviction that geography played a crucial role in the origin of species.

Though Darwin titled his book ''The Origin of Species,'' little in the book, in fact, addresses the question of how new species arise. Dr. Mayr determined that when populations of a single species are separated from one another, they slowly accumulate differences until they can no longer interbreed. Dr. Mayr called this allopatric speciation and detailed his arguments in his seminal book ''Systematics and the Origin of Species,'' published in 1942. Today allopatric speciation (''allo,'' from the Greek for ''other,'' and ''patric,'' from the Greek for ''fatherland'') is accepted as the most common way in which new species arise.

''Organic diversity had at last received a convincing explanation,'' Dr. Jerry A. Coyne, an evolutionary biologist at the University of Chicago, wrote of Dr. Mayr's arguments. Dr. Coyne called the book ''one of the greatest achievements of evolutionary biology.''

Similarly, the most commonly held view of what constitutes a species remains the one that Dr. Mayr promoted more than 50 years ago, known as the biological species concept. First explicitly defined by Dr. Theodosius Dobzhansky, it states that populations that can successfully interbreed are the same species and those that cannot are different species. While numerous other species concepts have been proposed and debated, this one continues to reign supreme.

Dr. Mayr's focus on species, both their nature and their origins, appears to have derived from his experiences in the South Pacific. When he went to New Guinea, Dr. Mayr once explained in an interview with Omni magazine, there was a popular school of thinking known as the nominalist school of philosophy that held that species did not, in reality, exist. They were merely arbitrary categories, little more than names.

''But I discovered that the very same aggregations or groupings of individuals that the trained zoologist called separate species were called species by the New Guinea natives,'' Dr. Mayr said. ''I collected 137 species of birds. The natives had 136 names for these birds -- they confused only two of them. The coincidence of what Western scientists called species and what the natives called species was so total that I realized the species was a very real thing in nature.''

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