Genetic equations alone can't explain evolution
The study of evolutionary biology traveled a divided road following publication of The Origin of Species, with disagreement and poor communication among specialists from different scientific fields. Not until the 1930s and ‘40s did the roads draw together in what came to be known as the “Evolutionary Synthesis.”
“We inherit the effects of the Synthesis,” says Miranda Paton, the Center’s 2011-12 Horning Fellow in the History and Philosophy of Science. “All of us—scientists and non-scientists alike—have been invited to understand Charles Darwin’s 1859 idea as well as evolutionary biology’s enduring research questions and philosophical problems in terms established by an influential generation of scientists eager to describe the causes of evolution in genetic terms.”
The central question was whether Mendelian genetics could be reconciled with gradual evolution by means of natural selection. A second issue was whether the broad-scale changes seen by paleontologists could be explained by changes seen in local populations.
“By the early 1890s, the problems of inheritance and gradual adaptation had already solidified as the central research problems that linked all students of evolution,” said Paton. “Those problems also produced a series of debates among biologists approaching the study of evolution from different disciplines that seemed to disrupt the process of scientific unification all students of evolution expected and sought.”
After 1900, those who addressed these questions by way of short-term experimental studies gained control of theoretical debate. “Geneticists—and many others—separated the problems of adaptation and speciation during this period, contributing to the general faith that short-term and population level analysis of mutation and selection could be taken as adequate proxies for all of evolution in the wild.”
By the early 1930s, mathematically-inclined geneticists had developed elegant techniques for modeling evolution in quantitative terms. “But can that kind of science really deliver all that Darwin promised? Can we just ‘scale up’ from an equation describing the dance between genetic mutation and natural selection’s culling hand to explain how new species are formed, the patterns of life’s branching pedigree we see, or the slow perfection of marvelous adaptations like eyes and wings?”
The Synthesis (a term that originated with Julian Huxley’s 1942 book Evolution: The Modern Synthesis) drew together ideas from branches of biology that had previously diverged. For Paton, the division between geneticists and paleontologists—“the two disciplines separated by the greatest distance of any pair in evolutionary biology”—is of particular interest.
Her book in progress, Vertebrate Paleontology and the Evolutionary Synthesis, 1894-1944, follows the waxing and waning reputations of two American students of vertebrate paleontology—Henry Fairfield Osborn (1857-1935)and George Gaylord Simpson (1902-1984)—as they negotiated with the rise of genetics during the first half of the 20th century. Though hardly headliners in the history of evolutionary theory, Osborn and Simpson were deeply influential in their respective generations, and paleontology itself was a central pillar of evolutionary research in the 19th century.
“And that’s why Osborn and Simpson are the stars of this story, and the relationship between paleontology and genetics are of interest to me,” said Paton. “Accounting for the development of a branch of biology or a scientist we admire is easy but risks presentism—that is, we’re likely to account for their greatness in the terms we currently accept. Explaining how important scientists and ideas were gradually made wrong or irrelevant promises a deeper, more critical look at the structure of a science.”
A new round of unified work on evolution now underway is leading to neologisms that show up in headlines, book titles and webpages. “Students of ‘Evo Devo’ are taking a sophisticated look at the relationship between genes and selection, asking how individual organisms develop from their genetic blueprints and become those living organisms whose fitness is actually tested by their environment.
“The development of ecology, population biology and ethology demand even more complexity. Those who advocate for ‘Evo-Devo-Eco’ acknowledge that a full understanding of evolution will come from an even broader understanding of the particular sorting criteria natural selection creates, and how those determiners of life, death and reproduction change over time. In other words, what makes an organism—or even a set of genes—‘fit’ or ‘unfit’ really requires fuller understanding of that organism’s membership in a very complicated ecological niche. Paleobiologists who can investigate long-term patterns of climate change and geographic distribution add another piece to be fit into the grand evolutionary puzzle.”
Paton did her doctoral work at Cornell University with William B. Provine, historian of population genetics and evolution. Before coming to OSU as a Postdoctoral Fellow, she taught at the Paleontological Research Institution in Ithaca, New York, and at Yale University. During winter term, she will teach the history of science course “Theory of Evolution and Foundation of Modern Biology.”
“I’m especially looking forward to this seminar. It’s a chance to see what Oregon’s science and humanities students will do with the important, complicated and beautiful problems evolutionary biology presents to all of us.”