Kovalevsky’s reputation has always remained firm in the small fraternity of vertebrate paleontologists. In the first years of this century, Henry Fairfield Osborn, America’s leader in the field, marked Kovalevsky’s work as “the first attempt at an arrangement of a great group of mammals upon the basis of the descent theory.” He then added:
If a student asks me how to study paleontology, I can do no better than direct him to the Versuch einer natürlichen Classification der fossilen Hufthiere [An Attempt at a Natural Classification of Fossil Hoofed Mammals—Kovalevsky’s most important German publication] . . . This work is a model union of the detailed study of form and function with theory.
The Belgian paleontologist Louis Dollo, Europe’s leader in the field, praised Kovalevsky as “the first to study systematically the great problems of paleontology on the basis of evolution . . . No paleontologist had ever joined such an intimate knowledge of details with such an amplitude of concepts.” In his major work (La paléontologie éthologique, 1909), Dollo proposed a heroic epitome by depicting the history of paleontology as a forward march from foolishness to illumination in three progressive stages, each marked by a prototype: the “époque fabuleuse, ou empirique,” centered upon the fanciful early-eighteenth-century work of the Swiss savant J. J. Scheuchzer; the “époque morphologique, ou rationelle,” marked by the great Georges Cuvier in the early nineteenth century; and the culminating “époque transformiste [evolutionary], ou définitive” symbolized by the brilliant work of Kovalevsky.
We may identity the source of Kovalevsky’s fame, and his enduring place in the history of the natural sciences, in two summary statements.
1. Kovalevsky made the first substantial application of evolutionary theory—specifically, Darwin’s version based on natural selection—to lineages of fossil organisms. (Others had published evolutionary interpretations based on vague and confused views about mechanisms of change, but Kovalevsky rigorously applied Darwin’s theory of natural selection, primarily by seeking correlations of altered anatomy with changing external environment, and then developing functional, or adaptive, interpretations of the evolutionary transformations.) Moreover, Kovalevsky was a consistent Darwinian at a time when the great majority of scientists, although persuaded of evolution’s truth by Darwin’s arguments, rejected natural selection as an important mechanism of change. (In fairness, Kovalevsky’s commitment need not record any superior insight or observation based on fossils, but arose largely from Darwin’s exalted status among the Russian intelligentsia, as discussed previously in this essay.)
In his English monograph of 1874, Kovalevsky wrote:
The wide acceptance by thinking naturalists of Darwin’s theory has given a new life to paleontological research; the investigation of fossil forms has been elevated from a merely inquisitive study of what were deemed to be arbitrary acts of creation to a deep scientific investigation of forms allied naturally and in direct connection with those now peopling the globe.
As a good example of his focus on adaptation to changing environments as the motor of evolution, Kovalevsky argues, later in the same monograph, that horses evolved their strong single toe for life on hard, dry plains (a new environment following the evolution of grasses in the Miocene epoch), while hoofed mammals living in soft and swampy ground required a broad foot and therefore retained several toes:
If the lateral digits are still retained in the Suidae [pigs] it is chiefly owing to the fact that the Hogs live generally in marshy places and on muddy river-banks, where a broad foot is of great importance for not allowing them to sink deeply into the mud. But if, by some geological change, their habitat should be transformed into dry grassy plains, there can be no reasonable doubt that they would as readily lose their lateral digits as the Paleotheroids [horse ancestors, in Kovalevsky’s view] have lost theirs . . . in becoming transformed into the monodactyle [one-toed] Horse.
2. Kovalevsky documented the most famous evolutionary story of all—the transformation of a small, many-toed ancestor with low—crowned teeth into the large-bodied, single-toed, long-toothed modern horse. Moreover, Kovalevsky identified, correctly we still think, the primary adaptive basis of this transformation—an environmental shift from browsing leaves in woodlands and marshes, to grazing of grasses and running on the open plains. Kovalevsky tied this transition to the Miocene evolution of grasses, and the subsequent development of extensive plains and savannahs as a new habitat ripe for exploitation. He explained reduction of toes as an adaptation for running on hard ground, and the evolution of high-crowned teeth as a necessary response to new diets of tough grasses with their high content of potentially tooth-eroding silica.
Thomas Henry Huxley had worked on the same problem, and had proposed a similar evolutionary sequence, but Kovalevsky provided so much more documentation that primary credit for this seminal story fell to the Russian scientist (with Huxley’s blessing). Kovalevsky and Huxley reconstructed the evolutionary sequence of horses as passing through a linear series of four successive stages, all based on European fossils (see the accompanying evolutionary tree, reproduced from Kovalevsky’s German monograph of 1876): from the Eocene Paleotherium, to the early-Miocene three-toed Anchitherium, to the late-Miocene Hipparion, to Equus, the modern horse.
Kovalevsky had no misgivings about the factuality of his sequence. He wrote about the first step in his English monograph of 1874: “There can be, in my opinion, no reasonable doubt that the Horse descended from the Paleotherium.” He expressed equal assurance about step two in his French treatise of 1873: “In its skeleton, Anchitherium is a genus so intermediary, so transitional, that if the theory of transmutation were not already so firmly established, this genus would have provided one of the most important pillars of support” (my translations throughout). His German monograph of 1876 exuded confidence in the full sequence of four steps: “We have a form in the upper Eocene, which must surely be counted as an ancestor of horses; and we now have apparently persuasive data that this form, Paleotherium medium, evolved through the Miocene Anchitherium and Hipparion to modern horses.” The French monograph of 1873 made the same claim in a more succinct and forceful manner: “There can be no reasonable doubt that the four forms—Paleotherium medium, Anchitherium, Hipparion and the horse—form a relationship of direct descent.”
I would add a third point, more technical and professional and therefore not part of Kovalevsky’s public reputation, to explain his high status among working paleontologists. Kovalevsky won kudos for his meticulous attention to descriptive detail. I have quoted the few general comments from his publications; the bulk of his text provides exhaustive information about every bump on every bone and every nubbin on every tooth. Moreover, Kovalevsky did not engage in such laborious work for the mindless and obsessive reasons that motivate many practitioners, but explicitly because he viewed this level of detail as a prerequisite for adequate documentation of such grand ideas as evolution, natural selection, and adaptation. Directly following his paean to Darwin from his English monograph (quoted earlier), and as an excuse for such flowery generality, he wrote: “The foregoing observations are intended only as a sort of apology for the somewhat minute osteological details into which it seemed to me necessary to enter in my description.”
Kovalevsky began his French treatise of 1873 with his most explicit defense of detailed empiricism as a scientific method. He states that he was able to succeed in documenting the intermediary status of Anchitherium only because he had so many more fossils to study:
I was able to obtain more complete material than any of my predecessors possessed. A monograph on Anchitherium now offers, following all the beautiful conquests of Darwinian theory, an irresistible charm for all evolutionary naturalists.
But Kovalevsky, true to the foremost ideal of objectivity, then denies that any a priori preference for evolution could have influenced his interpretations. In the best tradition of Sergeant Friday—“just the facts, ma’am”—he states that he had reached an ines
capable conclusion by freeing his mind of preconceptions and letting the fossils speak in their undeniable factuality:
Nevertheless, one must not think that I began this work with a preconceived aim. Quite to the contrary; I interrogated the material in an impartial manner, and I give the response that the fossils furnished to me.
With this brave claim, we come to a wonderful irony that raises the story of Vladimir Kovalevsky from an antiquarian tale for the heartstrings, to a lesson of central relevance for the practice of modern science. Kovalevsky developed a case study that remains preeminent as a triumphant tale of evolution documented in the fossil record. (Does any paleontological museum not include an evolutionary “line” of horses?) He expressed complete confidence in his sequence of four European genera. He won his reputation for unsurpassed care in meticulous and detailed description. He strongly espoused the classic doctrine of utter objectivity in observation, and he claimed that the fossils themselves had dictated an unimpeachable factual conclusion.
And Kovalevsky was wrong—for a clear and interesting reason that brings no discredit upon his work. He and Huxley had regarded the sequence of four European fossils as an unbroken lineage of direct transformation—that is, as a series of ancestors and descendants. They did not realize—and could not have done so in the absence of published evidence—that horses had evolved in America and had migrated several times into Europe. The three “ancestors” of Kovalevsky’s sequence—Paleotherium, Anchitherium, and the European Hipparion—are all side branches that migrated to Europe and became extinct without issue in their new and peripheral home. (As a historical irony that would cost the Aztecs dearly and greatly facilitate the bloody schemes of the Conquistadores, horses then died out in America, leaving the Old World descendants of yet another migration as the source of all modern horses.) Kovalevsky’s four genera did represent a temporal series of stages in a trend, but not—as he had asserted so confidently—a direct sequence of filiation. He had, so to speak, misidentified an indirect series of my paternal grandpa’s brother, my mother’s brother, and me, as a direct genealogy of my paternal grandpa, my father, and me.
The denouement occurred in an interesting manner when T. H. Huxley made his only trip to the United States to present an inaugural lecture for the opening of Johns Hopkins University, and to participate in several other events—including a lecture in New York on the evolution of horses—surrounding America’s centennial celebration of 1876. He visited the American paleontologist O. C. Marsh at Yale and, in great excitement mixed with a bit of chagrin, saw enough beautifully transitional fossils to know that Europe had been a periphery, and America a breeding ground. Marsh later wrote of his magnificent show-and-tell:
He [Huxley] then informed me that this was new to him, and that my facts demonstrated the evolution of the horse beyond question, and for the first time indicated the direct line of descent of an existing animal. With the generosity of true greatness, he gave up his own opinions in the face of new truth and took my conclusions.
Huxley scrapped his New York lecture, and hastily prepared a new version.
If science, as a stereotype proclaims, truly operated as an automatic process of objective documentation, then we should castigate Kovalevsky—for he firmly advertised his conclusions as factually driven and truly proven thereby. Moreover, if theories rest upon crucial cases, as another stereotype holds, then don’t we call evolution itself into question by scratching Kovalevsky’s horses from the race of life? Doesn’t Kovalevsky then become an incubus rather than a hero—an unwitting foil for creationists rather than a preeminent student of evolutionary paleontology—because his error might give comfort to the enemy?
We need, instead, to reject these simplistic stereotypes and heed Marsh’s wise statement about “the generosity of true greatness.” The only universal attribute of scientific statements resides in their potential fallibility. If a claim cannot be disproven, it does not belong to the enterprise of science. New fields (like evolutionary paleontology in Kovalevsky’s day) based on imperfect data (the fossil record) are especially subject to error—and brave scientists must do their best and risk the consequences, secure in the knowledge that corrected mistakes (however personally embarrassing to the perpetrator) bring as much clarity as valid discoveries.
Moreover, truly grand and powerful theories—evolution preeminently among them—do not and cannot rest upon single observations. Evolution is an inference from thousands of independent sources, the only conceptual structure that can make unified sense of all this disparate information. The failure of a particular claim usually records a local error, not the bankruptcy of a central theory. Kovalevsky mistook a series of collateral relatives for a true genealogical sequence, but the notion of genealogy itself does not fall thereby. If I mistakenly identify your father’s brother as your own dad, you don’t become genealogically rootless and created de novo. You still have a father; we just haven’t located him properly.
With this tale of Kovalevsky’s fruitful error, we come face to face with the interesting and conjoined issues of the relationship between fact and theory in science, and the phenomenon of being right for the wrong reason. Theory and fact are equally strong and utterly interdependent; one has no meaning without the other. We need theory to organize and interpret facts, even to know what we can or might observe. And we need facts to validate theories and give them substance. Kovalevsky made an eminently useful and rather wonderful mistake. He grasped the explanatory power of a new and correct theory that would reformulate all of biology—and he yearned to apply this idea to difficult but crucial data. He reached a premature conclusion that was only half wrong in misidentifying collateral relatives as direct ancestors. But he provided the first powerful example of a workable methodology (inferences about adaptation from anatomical changes in paleontological sequences) that can, with better data, document and support the most important theory subject to adjudication by the fossil record.
Lest anyone doubt the power of being right for the wrong reason, consider the central incident in the intellectual life of Kovalevsky’s hero, Charles Darwin. Thanks to his obsessive habits of record keeping, we can reconstruct the sources of Darwin’s eureka when, in early 1837, he recognized that evolution must be true. Darwin first learned that he had been wrong in allocating many small birds from the Galápagos Islands to several distantly related families. All, in fact, were finches. How could adjacent islands house separate species of such closely related birds? He then learned that the distinctive rhea (a large flightless bird) he had collected in southern Patagonia belonged to a new species (named Rhea darwinii in his honor by his ornithological consultant, John Gould). Why, Darwin wondered, did two so closely related birds share contiguous geographic territories, the ordinary rhea to the north, and Darwin’s new species to the south?
Darwin pondered these two examples of geographic replacement among closely related modern birds. He then made a brilliant analogy: If both finches and rheas replace each other in space, then shouldn’t temporal succession also occur in continuity—that is, by evolution rather than successive creation? Darwin had collected large fossil mammals in South America. He regarded one genus, later named Macrauchenia, as a relative of the modern guanaco. If the two rheas are maximally related and geographically contiguous, then the two camel-like creatures, the extinct Macrauchenia and the modern guanaco, as temporally contiguous, must also be joined by blood. In other words, temporal sequence must record evolutionary transformation. Eureka! Darwin jotted the key insight into a private notebook: “The same kind of relation that common ostrich [rhea] bears to Petisse [the new species, Rhea darwinii], extinct guanaco to recent; in former case position, in latter time.”
What a portentous moment; what a crux in the history of human thought! But Darwin based his brilliant analogy, and his astoundingly correct general conclusion, on a flub in particulars—an error that he could not have recognized, and that did not affect the validity of his larger insight. South America
had been an island continent for tens of millions of years before the Isthmus of Panama rose just a few million years ago (see chapter 20). Several independent orders of mammals had evolved on South America, though most perished following climatic changes and the influx of North American species after the isthmus formed. (The outstanding set of survivors, South America’s grand indigenous group, includes sloths, armadillos, and anteaters of the unique order Edentata.)
One of these extinct and independent orders, the Litopterna, included creatures uncannily convergent upon unrelated mammals of other continents. (In the evolutionary phenomenon of convergence, distantly related groups evolve similar forms, as a result of independent adaptation to common environments. Ichthyosaurs are reptiles, and dolphins are mammals—but they both look and work like fishes.) One group of litopterns evolved an amazing resemblance to horses, including a parallel loss of toes, culminating in Thoatherium, the one-toed litoptern! Another group, represented by Macrauchenia, converged upon the New World camels. Since true camels later crossed the Isthmus of Panama and colonized South America (to survive today as llamas, guanacos, and alpacas), we can hardly blame Darwin for inferring a genealogical tie between modern guanacos and the remarkably similar but unrelated fossil Macrauchenia. Richard Owen, England’s greatest anatomist and Darwin’s friend in these early years (see chapter 6), had affirmed the link of Macrauchenia to modern guanacos.
Leonardo’s Mountain of Clams and the Diet of Worms Page 15