Once We All Had Gills: Growing Up Evolutionist in an Evolving World

14. Embryos Evolving

183 Embryos Evolving How to Do Evo-Devo At Indiana I began thinking about evo-devo as something that should move beyond its mid-twentieth-century form. Over a period of time I developed a parts list of essential elements we would need in order to be able to both ask and answer questions about the evolution of body form. It seemed that it would take a synthetic combination of ideas from several disciplines. These eventually would include developmental genetics , molecular evolution, and genomics on the mechanistic side. But more was needed. The historical disciplines of paleontology and phylogeny would allow us to include the events of the long ago evolutionary past in our analyses. Paleontology would allow us to envision ancestral conditions and patterns of change, and evidence from phylogeny would allow us to map a history of descent. The second essential element was a suitable research organism for addressing experimental questions. That would require an organism that presented concrete evo-devo problems stemming from its evolutionary history and was amenable to experiments designed to answer those questions. The third was to seek mechanisms of evo-devo that were comparable in explanatory power to those of modern developmental and molecular biology. This would allow us to understand the mechanistic bases for particular evolutionary changes. I considered phylogeny to be crucial to the experimental effort, because it is only by incorporating the pattern of descent of evolutionary changes that evolutionary changes in development can be interpreted as arising once in an evolving lineage or evolving independently in separate fourteen 184 Finding Evolution, Founding Evo-Devo lineages. We should be able to set mechanistic explanations into these phylogenies. In cases of convergent evolution of new features, phylogeny would let us unravel the choices nature has in independently responding to similar selective pressures. That would take new phylogenetic data to accomplish.Somyfourthobjectivewastousemolecularbiologytoinfer the phylogenies of the major animal phyla to get a better framework of relationships than previous data had allowed. These goals did not spring fullyformedtomind,andIwasnaïveaboutmuchofwhathadtobedone. In 1975, I tried to rigorously organize my thinking by starting a course in evo-devo for graduate students (the term we first used was devo-evo, but by consensus that eventually flipped to evo-devo because “evolutionary developmental biology” was less clumsy than “developmental evolution ”). I also began writing a book to explore and synthesize the componentsofadiscipline ,andIstartedwhatwasatfirstanuncertainquestfor an experimental system that I could develop to ask evo-devo questions. AsfarasIknowthestartofmygraduatecourseseemstohavetiedan analogous course at Berkeley as one of the first evo-devo courses taught anywhere. I asked my geneticist colleague Thomas Kaufman to join me in teaching that class as part of writing a book. Thom was beginning a massive study of the homoeotic genes that control the layout of body development, and he would assume a major role in a revolution of our understanding of the genes that regulate development in the animal kingdom. We taught the 1977 class together and drafted an outline for what would become the book Embryos, Genes, and Evolution, published in 1983. I hoped that we could provide a guide to the making of a modern evo-devo discipline. The publisher, Macmillan, gave us a small advance and some money to pay a typist for transcription. We opened a joint account at a bank downtown so either of us could write the typist’s checks as needed. We had both our names put on the checks, which amusingly raised a few eyebrows at the bank when we went down together to open a joint checking account. Beth illustrated the book with a large series of superb line drawings. Embryos, Genes, and Evolutionwas important because it was the first attempt to link evolution with the new developmental genetics, and it was the first book to map the course that evo-devo would take. We inte- Embryos Evolving 185 grated theoldertraditions ofthestudyofevolutionofdevelopmentwith new experimental approaches being created in developmental biology. At the time there was no actual discipline of what came to be called evodevo . There was an earlier tradition of embryologists studying evolution ofdevelopment,butbecauseoftechnicallimitations,thatfieldhadeventually petered out. We had to borrow most experimental examples in the book from work done for other reasons than evo-devo. We hoped to stimulate development of a new field that would create its own research questions and experimental systems. We were right in our pointing out of future directions, although our examples seem primitive now. A Day in...