Primer: Drosophila September 3, 2008Posted by Will Thomas in EWP Primer.
Tags: Drosophila, genetics, Robert Kohler, Thomas Hunt Morgan
What value do historians of science gain from locating a point of origin? Scientists, I think, like origins, because it’s customary to give credit where credit is due in scientific papers. Historians can find origins very useful, because they often reveal a certain motivation or meaning in a tradition, which was later lost even as the tradition persisted. There’s probably a certain satisfaction to be found in looking at some point in history, and finding that “before this point in time, this idea did not exist.” But there are dangers as well. Meanings change notoriously over time, so when we look for the origin of this or that belief that we hold today, though we may recognize it in the past, it would look quite different to those who “came up” with it. Origins are also slippery in other ways. We often find that when we track them down, some new “predecessor” presents itself, and we’re stuck chasing a constantly retreating mirage. Thus, when we bother to track things down, we should make sure we gain value from the act of tracking.
In the case of genetics, there’s a well-known tradition that dates the study of genetics back to the monk Gregor Mendel and his famous green and yellow peas (get out your Punnett squares, class). There’s even a historical scandal suggesting that Mendel cooked his data: statistically it’s too good. But why should we really care about Mendel? I mean, it’s good to know about him, and it’s good to know how others have viewed him and used his precedent to further their own work, but there’s not much value in worrying too much about him, specifically. His work wasn’t used or even known until 35 years after its publication in an obscure journal, when it was unearthed by Hugo DeVries and Carl Correns, who were part of a thriving botanical/laboratory-biology culture circa 1900 that was already deep in theorization about how traits were passed down from generation to generation. (In 1905, the British biologist William Bateson coined the term “genetics” to describe what this intellectual program was all about, and “Mendelian” came to describe a particular approach within this broader program.)
In the history of genetics, there are a lot of places to pin down points of origin for various insights, to the point where it may be much more interesting to try and identify points of significance. In the history of genetics, the exploitation of Drosophila, or fruit fly, by the American embryologist Thomas Hunt Morgan, surely qualifies. Over decades, Morgan and his large research team refined what had begun as piecemeal speculation and study into a robust, carefully controlled research program. By carefully breeding fruit flies, they created standard breeds with standard genetic characteristics that could be traced through subsequent generations. The group mapped Drosophila chromosomes (already presumed to be the place where traits were passed down), locating specific genes on them, and demonstrated how those genes were passed down and expressed. They also elucidated the process of evolution, charting spontaneous mutations within their Drosophila population. In 1915 Morgan and his group published the results of their early research in The Mechanisms of Mendelian Inheritance.
Morgan’s significance reaches much further, however. He created a culture of genetics research, wherein the Drosophila work became a baseline, a model for genetic understanding. In practice, knowing the genetics of the Drosophila became a proxy for a more general understanding of genetic mechanisms in all organisms, to the point that other groups also used the Drosophila for their own general genetic research: even now, Drosophila crops up unusually often in research papers. Further still, the thoroughness the Drosophila work helped cement a specifically British-American tradition in early-20th-century genetic research that focused on the functions of the chromosomes rather than expressed traits.
The key source on T. H. Morgan and his Drosophila research is a fairly recent classic in the science studies literature: Robert Kohler’s Lords of the Fly: Drosophila Genetics and the Experimental Life (1994). The book is widely cited for demonstrating the standardization of a living organism so as to serve as a piece of laboratory equipment, as well as for demonstrating how Morgan and his crew built a global genetics empire, how they coordinated the mores of a group laboratory culture, etc, etc. If you’re a historian, you know this drill. Kohler’s sociological point (already fairly commonplace in ’94) has been copied and pasted into the science studies case study literature again and again. Talk about standardized apparatus! What continues to make Kohler’s book essential reading is the fact that the Morgan group’s use of fruit flies is, by any measure, crucial to know about because of its originating and continuing importance as a central tradition in genetics research, which is a central tradition of 20th-century biology. Now, if I could only keep the buggers out of my garbage!