Sunday, May 20, 2012

Scientific turnover and the fate of old theory

The Arts and Sciences are often seen as non-overlapping complements, as naturally opposed as North and South, or the two sexes male and female. It's therefore surprising to find someone who can make a significant career in both, not just as an amateur but as a paid professional.

Vladimir Nabokov is best known as the author of the novel Lolita, but before becoming famous for his writing in English, he was a professional lepidopterist, an expert on a group of butterflies known as the Blues. An earlier blog post here highlighted some recent research on "his" group of butterflies.

His two careers were also the subject of an essay by Stephen Jay Gould. Gould used Nabokov's example to examine our attitudes to "genius". If Nabokov was a genius in literature, does it follow that his scientific work was also illuminated by the same genius? Was his scientific writing especially fluent or literary, as some literary critics claim? Gould found that, in the opinion of other professional lepidopterists, Nabokov's scientific work was competent and painstaking, but not especially pathbreaking or profound. Nor was his scientific writing unusually poetic or stylistically striking, in the way that his novels were.

In fact, Gould goes as far as to characterize Nabokov as being somewhat of a "stick in the mud." At the time when he was engaged in his butterfly work full-time at the Museum of Comparative Zoology at Harvard, from 1942 to 1948, a revolution was underway in taxonomy. Where previously the morphological characters, such as wing coloration or genital anatomy (a serious preoccupation of much of entomology!) were the means by which new species were defined, the budding science of cytology (the study of cells) had introduced chromosomes as yet another important character. "Cryptic" species with identical morphology were now being defined on the basis of their differing karyotypes (the number and appearance of the chromosomes). Nabokov rejected the use of chromosomes for defining new species, perhaps as a matter of practicality: pinned butterfly specimens in museums only preserve the morphology, so it would be impossible to distinguish karyotype variants in the museum cabinet.

His autobiography, however, seems to belie this depiction of Nabokov as a rigid conservative. Nabokov spoke about "great upheavals... taking place in the development of systematics." The year that Nabokov started working in the Museum was also the year that Ernst Mayr, by then also an emigre to the United States, published his Systematics and the Origin of Species, the book which established the biological species concept, that species (at least for sexual macroorganisms like birds and insects) are defined by their potential for breeding to produce viable offspring. The new emerging school of taxonomy represented by Mayr were strong champions of geographic variation. Species were not immutable, platonic ideals. The variation represented by geographic "races" or subspecies was just as important as the original "type" of a species. Conceptually, this so-called Neo-Darwinian revolution was when darwinism finally became orthodoxy in taxonomy, the field that had inspired it, nearly a century after the publication of the Origin of Species.

Nabokov was aware of this theoretical revolution - how could he have ignored it? This was a tremendous change from the lepidoptery of his youth, which could well be said to be truly "butterfly collecting". As he observed:
"Since the middle of the [19th] century, Continental lepidopterology had been, on the whole, a simple and stable affair, smoothly run by the Germans. Its high priest, Dr. Staudinger, was also the head of the largest firm of insect dealers. Even now, half a century after his death, German lepidopterists have not quite managed to shake off the hypnotic spell occasioned by his authority. He was still alive when his school began to lose ground as a scientific force in the world. While he and his followers stuck to specific and generic names sanctioned by long usage and were content to classify butterflies by characters visible to the naked eye, English-speaking authors were introducing nomenclaturial changes as a result of a strict application of the law of priority and taxonomic changes based on the microscopic study of organs. The Germans did their best to ignore the new trends and continued to cherish the philately-like side of entomology. Their solicitude for the "average collector who should not be made to dissect" is comparable to the way nervous publishers of popular novels pamper the "average reader"--who should not be made to think. 
"There was another more general change, which coincided with my ardent adolescent interest in butterflies and moths. The Victorian and Staudingerian kind of species, hermetic and homogeneous, with sundry (alpine, polar, insular, etc.) "varieties" affixed to it from the outside, as it were, like incidental appendages, was replaced by a new multiform and fluid kind of species, organically consisting of geographical races or subspecies. The evolutionary aspects of the case were thus brought out more clearly, by means of more flexible methods of classification, and further links between butterflies and the central problems of nature were provided by biological investigations."  
(Speak, Memory: An Autobiography Revisited, pp.122-123)
So it wasn't that Nabokov was a conservative who didn't like change. He had already spanned the era between "hobbyist" and scientific entomology. He was already witness to a revolution (in science, and also in his homeland of Russia). There's a quip I've heard attributed to the physicist Max Planck, that science doesn't progress because people come to accept new theories on the strength of their evidence; it progresses because old scientists who believe the old theories die out. It's certainly an exaggeration, but we are equally certainly products of our education. Every generation in science has its own revolution of understanding, and maybe it's unfair to expect someone to accommodate a second one, just as he or she was getting comfortable with the first!

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