The year was either 1989 or 1990. I have not been able to locate, in my messy office, my original handwritten notes from the lecture. (I’ll find them, however — it’s just a matter of digging through boxes.) The speaker was Professor Mark B. Adams of the University of Pennsylvania, a historian of science and expert on the development of neo-Darwinian theory in the United States and Russia. The lecture occurred in Chicago’s annual Conceptual Foundations of Science lecture series, organized by Bob Richards, a member of my PhD committee.
Adams’s announced title was something like “Big Evolution and Little Evolution: The History of the Difference.” Adams had spent a great deal of time working closely with Theodosius Dobzhansky, interviewing him in particular about the micro- versus macro-evolution distinction that figures prominently in Dobzhansky’s 1937 book, Genetics and the Origin of Species, one of the founding documents of the Modern Synthesis. Laying out his case, Dobzhansky argues that macroevolution (i.e., transformation above the species level) is nothing more than micro (within species) evolution, scaled with time, with higher taxonomic category differences arising roughly proportionately to the time elapsed.
But Dobzhansky also expresses this equivalence “reluctantly” (1937, p. 12). Why that enigmatic adverb, however, for a smooth continuum of evolutionary transformation, about which Dobzhansky was apparently so convinced?
Adams learned that Yuri Filipchenko (1882-1930), the Russian geneticist whom Dobzhansky idolized as his mentor, had coined the terms “microevolution” and “macroevolution” precisely because Filipchenko denied the equivalence of the two processes. Inescapable qualitative differences existed in these phenomena, which entailed that they must be treated as separate domains of biological inquiry.
But, by equating them, where time elapsed is the only real difference, Dobzhansky was contradicting his mentor, albeit doing so “reluctantly.” In 1973, two years before Dobzhansky’s death, Adams put the question to him directly, at a field station in Yosemite:
It was from his mentor that [Dobzhansky] adopted the microevolution, macroevolution terms that his 1937 book made standard. He also noted that his mentor had created those neologisms in 1927 (when Doby was his assistant and protégé) to distinguish varieties and species from genera and higher taxa, to make the case that, however useful in understanding the former, genetics could not illuminate the latter, namely, evolution. Yet, a decade later, now at Columbia, Dobzhansky deployed his mentor’s neologisms to argue just the opposite! I was puzzled, and I asked him, given his enormous respect for his mentor, how he accounted for the difference. I was expecting a technical answer. (Was it the influence of the Morgan School, his work with lady beetles, or some experience he had had?) Instead, he shrugged and said, almost indifferently, “He bet on the wrong horse.” …“Bet”? “On the wrong horse?” I was startled, having never (in my innocence) thought of science as a “horse race” or a “betting” matter. That comment changed my perception. This was not a scientist who had been certain of his own approach, but rather someone who realized it might have gone either way, and chose the option that, if it turned out to be right, would both justify and empower his newly coined specialty, “population genetics.” In subsequent years, I began to explore the evolutionary synthesis in greater detail, losing patience with triumphalist accounts, and gradually developing the views and evidence for this paper. (p. 224)
The Wrong Horse
Filipchenko bet on the wrong horse in part, because in the U.S., creationists were pressuring evolutionary theory from without. In his lecture, Adams explained that Dobzhansky had corresponded for years with the geneticist Frank Lewis Marsh (1899-1992), an Adventist creationist educated at the Universities of Chicago and Nebraska (PhD). The Dobzhansky estate would not allow this correspondence to be published, however, so only historians who traveled to the Dobzhansky archive could see the material. Adams writes:
In this context, we should consider the utility of the definition of the word “evolution” deployed by Dobzhansky — “a change in the genetic composition of populations” (Dobzhansky 1937: 11). The self-evident conclusion is clear: evolution is not a “theory” but a demonstrable (indeed a demonstrated!) fact. Perhaps in the United States, the battle to establish the validity of evolution in the face of creationist religious opposition solidified the identification between the general theory and those experimental researches that could demonstrate, and thereby “prove,” that theory “as a fact.” This situation may well have encouraged individual scientists to downplay their reservations about the macroevolutionary question in order to protect evolutionary biology as a whole: uncertainties about mechanism may have seemed less pressing when the validity of evolution itself was under attack, especially when those uncertainties were being deployed by the creationists to disprove evolution. Dobzhansky’s extensive correspondence with one scientific creationist [i.e., Marsh] suggests that this criticism weighed, at least on this central figure in forging the evolutionary synthesis in America.” (pp. 217-8)
Adams’s lecture was so electrifying that immediately after it, my dissertation director, Bill Wimsatt, walked across the room to where I was sitting, and said with a smile, “Well, Paul — that’s one for you.” Since 1989-90, I have looked for the publication of the lecture. Nothing.
Until this year. Springer has at last published Mark Adams’s long-delayed “Little Evolution, BIG Evolution: Rethinking the History of Darwinism, Population Genetics, and the ‘Synthesis’” in the equally fascinating anthology, Natural Selection: Revisiting Its Explanatory Role in Evolutionary Biology (474 pp.), edited by Richard Delisle of the University of Lethbridge. The volume is available for purchase here. Some things are worth waiting for.