Biologists and historians often present natural history and molecular biology as distinct, perhaps conflicting, fields in biological research. Such accounts, although supported by abundant evidence, overlook important areas of overlap between these areas. Focusing upon examples drawn particularly from systematics and molecular evolution, I argue that naturalists and molecular biologists often share questions, methods, and forms of explanation. Acknowledging these interdisciplinary efforts provides a more balanced account of the development of biology during the post-World War II era.

Experimental taxonomy was a diverse area of research, and botanists who helped develop it were motivated by a variety of concerns. While experimental taxonomy was never totally a taxonomic enterprise, improvement in classification was certainly one major motivation behind the research. Hall's and Clements' belief that experimental methods added more objectivity to classification was almost universally accepted by experimental taxonomists. Such methods did add a new dimension to taxonomy — a dimension that field and herbarium studies, however rigorous, could not (...) duplicate. Nonetheless, experimental techniques were never completely divorced from traditional taxonomic methods. In practice, all experimental taxonomists employed a combination of descriptive and experimental methods. Most researchers freely acknowledged a debt to traditional taxonomy. Furthermore, the greater rigor of twentieth-century taxonomy was not due entirely to experimentalism. Both the experimental and descriptive aspects of taxonomy were improved by the increased use of quantitative methods, particularly statistics.52From the beginning, a number of experimental taxonomists were interested primarily in classification. But many approached their research from fields other than taxonomy. These botanists were concerned primarily with ecological and genetic problems rather than with classification. There is little indication that they drew a sharp distinction: for example, taxonomic and cytogenetic conclusions were interwoven in Babcock and Stebbins' 1938 study of Crepis 53 (this was even more true of Babcock's final mongraph on the genus, published in 1947). Similarly, the extensive series of monographs, “Experimental Studies on the Nature of Species,” initiated by the Carnegie Institution group in 1940 combined ecological, cytogenetic, and taxonomic conclusions. Indeed, the significance of the major projects completed by experimental taxonomists was largely due to the fact that they were comprehensive studies rather than strictly taxonomic or cytogenetic.In a general sense, the primary motivation behind much of experimental taxonomy was evolutionary. Beginning in the second decade of the century Hall and Clements exhorted taxonomists to take an explicitly evolutionary perspective on research. Hall undoubtedly spoke for the majority of experimental taxonomists when he stated, “If there be anything at all to organic evolution, then taxonomy is dealing with the products of evolution and it is this that gives to taxonomy both its highest mission and its greatest responsibility.”54Aside from a common interest in evolution, however, the theoretical orientations of experimental taxonomists were varied. This diversity is strikingly illustrated by the evolutionary views of members of the Carnegie Institution research group. Experimental taxonomy was initiated by Clements as one aspect of his Lamarckian study of adaptation and speciation. In contrast, Hall's research was inspired by a broad concern for evolutionary problems. Hall rarely referred to specific evolutionary mechanisms; rather, he applied a general conception of evolutionary processes to deduce phylogenetic relationships. His later associates at the Carnegie Institution explicitly dissociated themselves from Clements' theoretical framework. The neo-Darwinian interpretations of adaptation and speciation presented by Clausen, Keck, and Hiesey could hardly have been more different than those of Clements. However, this major shift in theoretical orientation should not obscure significant similarities between the research of Clements and later Carnegie workers. In terms of research problems and methodology, the first volume of “Experimental Studies on the Nature of Species” was an extension of the Clementsian research program. Clausen, Keck, and Hiesey's monograph was the mature discussion of transplant experimentation that Clements had very tentatively initiated during the first decades of the twentieth century. The bond that linked the members of the Carnegie Institution research group to experimental taxonomists in general was one of shared methodology rather than common theoretical orientation. While Clements' evolutionary views were eventually repudiated, his enthusiasm for innovative experimental methods was shared by later workers.The development of experimental taxonomy faced significant problems. During the period 1920–1950 this area of botanical research remained a hybrid discipline. The aims and scope of experimental taxonomy were never articulated in a completely unified manner. Consequently, even among experimental taxonomists, there were disagreements over the relation of their research to other botanical endeavors. Even though experimental taxonomy had close ties with general taxonomy, a number of experimental taxonomists questioned the “taxonomic” nature of their research55. Even to the extent that this hybrid discipline could be identified as a branch of taxonomy, problems arose. Taxonomists, as we have seen, were justifiably skeptical of what appeared to be a rapid influx of untested methods and ideas. Experimental taxonomists were not merely incorporating well-accepted methods from ecology and cytogenetics; during the period 1920–1950 the fields from which experimental taxonomists borrowed were themselves undergoing major theoretical and methodological changes. Despite problems and conflicts, experimental taxonomists did contribute improvements to classification. Furthermore, they made significant contributions to plant ecology and evolutionary genetics.The development of experimental taxonomy indicates that twentieth-century botanists were not necessarily isolated in naturalist and experimentalist camps. The joint session of taxonomists, cytologists, and geneticists at the 1926 International Congress of Plant Sciences indicates communication among specialists fairly early in the century. The papers and commentaries presented during this session do not reveal the hostility and intolerance that supposedly characterized encounters between experimentalists and naturalists. Nor do they suggest incompatible conceptual worlds separating geneticists and taxonomists.Discussions between taxonomists and other specialists were not limited to a single international congress. Particularly during the 1930s discussions among specialists appear to have been fairly widespread. Groups such as the Biosystematists and the Society for the Study of Systematics in Relation to General Biology served as forums for discussion among biologists from a variety of disciplines. The naturalist-experimentalist dichotomy tends to obscure the broad research interests of a number of prominent twentieth-century botanists. Most of the experimental taxonomists cannot be characterized adequately as either naturalists or experimentalists. Traditionally trained taxonomists such as Hall, Keck, and Turrill throughout their careers participated in both experimental and herbarium research. And a number of specialists in fields other than taxonomy took an active interest in taxonomic problems, not necessarily limited to experimental aspects. For example, Anderson suggested a number of innovations to make herbarium collections more amenable to statistical analysis.This historical study of experimental taxonomy indicates a different relationship between experimentalism and taxonomy than that portrayed by the naturalist-versus-experimentalist dichotomy. F. E. Clements originated experimental taxonomy as a revolt against descriptive botany. In retrospect, this revolution was not vigorously waged and was not successfully completed. Experimental taxonomy was never an entirely experimental approach to botanical research. Even the most ardent advocates of experimentalism relied heavily on methods inherited from traditional taxonomy. Moderate exponents of experimental taxonomy stressed the compatibility of experimental methods, field observation, and herbarium techniques. Attempts to fuse cytogenetics, ecology, and taxonomy during the period 1920–1950 resulted in an impressive body of research. However, this fusion constituted neither a repudiation of descriptive botany nor a complete revision of taxonomic theory of practice. (shrink)

During the early 1960s, Morris Goodman used a variety of immunological tests to demonstrate the very close genetic relationships among humans, chimpanzees, and gorillas. Molecular anthropologists often point to this early research as a critical step in establishing their new specialty. Based on his molecular results, Goodman challenged the widely accepted taxonomie classification that separated humans from chimpanzees and gorillas in two separate families. His claim that chimpanzees and gorillas should join humans in family Hominidae sparked a well-known conflict with (...) George Gaylord Simpson, Ernst Mayr, and other prominent evolutionary biologists. Less well known, but equally significant, were a series of disagreements between Goodman and other prominent molecular evolutionists concerning both methodological and theoretical issues. These included qualitative versus quantitative data, the role of natural selection, rates of evolution, and the reality of molecular clocks. These controversies continued throughout Goodman's career, even as he moved from immunological techniques to protein and DNA sequence analysis. This episode highlights the diversity of methods used by molecular evolutionists and the conflicting conclusions drawn from the data that these methods generated. (shrink)

Beginning in the mid-1930s the comparative physiologists Laurence Irving and Per Fredrik Scholander pioneered the study of diving mammals, particularly harbor seals. Although resting on earlier work dating back to the late nineteenth century, their research was distinctive in several ways. In contrast to medically oriented physiology, the approaches of Irving and Scholander were strongly influenced by natural history, zoology, ecology, and evolutionary biology. Diving mammals, they argued, shared the cardiopulmonary physiology of terrestrial mammals, but evolution had modified these basic (...) adaptive processes in extreme ways. In particular, seals’ remarkable ability to hold breath, lower metabolism, produce energy anaerobically, and resist asphyxiation, provided a sharp contrast with terrestrial mammals, including humans. This diving physiology was an extreme elaboration of a general regulatory mechanism that allowed seals and other diving mammals to remain active underwater for extended periods. The decrease in heart rate referred to as bradycardia or the “diving reflex” was highly developed in diving mammals, but also found in less developed form in many other organisms faced by asphyxia. It therefore served as a kind of “master switch” for lowering metabolism in diving, hibernation, parturition, drowning, and other physiological responses involving lack of oxygen. Studying bradycardia unified a wide diversity of physiological phenomena, while also providing a context for contrasting the physiological responses of various species, including humans. Conducted in the laboratory and the field, this research served as a bridge between a comparative physiological ecology focused on non-human species and a human-centered general physiology. (shrink)

Ecology has often been characterized as an immature scientific discipline. This paper explores some of the sources of this alleged immaturity. I argue that the perception of immaturity results primarily from the fact that historically ecologists have based their work upon two very different approaches to research.

During the decades following World War II diverse groups of American biologists established a variety of distinctive approaches to organismal biology. Rhetorically, organismal biology could be used defensively to distinguish established research traditions from perceived threats from newly emerging fields such as molecular biology. But, organismal biologists were also interested in integrating biological disciplines and using a focus on organisms to synthesize levels of organization from molecules and cells to populations and communities. Part of this broad movement was the development (...) of an area of research variously referred to as physiological ecology, environmental physiology, or ecophysiology. This area of research was distinctive in its self-conscious blend of field and laboratory practices and its explicit integration with other areas of biology such as ecology, animal behavior, and evolution in order to study adaptation. Comparing the intersecting careers of Knut Schmidt-Nielsen and George Bartholomew highlights two strikingly different approaches to physiological ecology. These alternative approaches to studying the interactions of organisms and environments also differed in important ways from the organismal biology championed by leading figures in the modern synthesis. (shrink)

Bergmann’s rule and Allen’s rule played important roles in mid-twentieth century discussions of adaptation, variation, and geographical distribution. Although inherited from the nineteenth-century natural history tradition these rules gained significance during the consolidation of the modern synthesis as evolutionary theorists focused attention on populations as units of evolution. For systematists, the rules provided a compelling rationale for identifying geographical races or subspecies, a function that was also picked up by some physical anthropologists. More generally, the rules provided strong evidence for (...) adaptation by natural selection. Supporters of the rules tacitly, or often explicitly, assumed that the clines described by the rules reflected adaptations for thermoregulation. This assumption was challenged by the physiologists Laurence Irving and Per Scholander based on their arctic research conducted after World War II. Their critique spurred a controversy played out in a series of articles in Evolution, in Ernst Mayr’s Animal Species and Evolution, and in the writings of other prominent evolutionary biologists and physical anthropologists. Considering this episode highlights the complexity and ambiguity of important biological concepts such as adaptation, homeostasis, and self-regulation. It also demonstrates how different disciplinary orientations and styles of scientific research influenced evolutionary explanations, and the consequent difficulties of constructing a truly synthetic evolutionary biology in the decades immediately following World War II. (shrink)

H. B. D. Kettlewell's field experiments on industrial melanism in the peppered moth, Biston betularia, have become the best known demonstration of natural selection in action. I argue that textbook accounts routinely portray this research as an example of controlled experimentation, even though this is historically misleading. I examine how idealized accounts of Kettlewell's research have been used by professional biologists and biology teachers. I also respond to some criticisms of David Rudge to my earlier discussions of this case study, (...) and I question Rudge's claims about the importance of purely observational studies for the eventual acceptance and popularization of Kettlewell's explanation for the evolution of industrial melanism. (shrink)

The distinction between taxonomic plant geography and ecological plant geography was never absolute: it would be historically inaccurate to portray them as totally divergent. Taxonomists occasionally borrowed ecological concepts, and ecologists never completely repudiated taxonomy. Indeed, some botanists pursued the two types of geographic study. The American taxonomist Henry Allan Gleason (1882–1975), for one, made noteworthy contributions to both. Most of Gleason's research appeared in short articles, however. He never published a major synthetic work comparable in scope or influence to (...) the ecological texts of Clements, Schimper, and Warming.Despite exceptions such as Gleason, most plant geographers throughout the twentieth century have emphasized the distinction between ecological and taxonomic plant geographies. Why have these distinct traditions developed? In his book Geographical Ecology, Robert MacArthur has suggested a psychological explanation for the dichotomy: “Unraveling the history of a phenemenon has always appealed to some people and describing the machinery of the phenomenon to others... The ecologist and physical scientist tend to be machinery oriented, whereas paleontologists and most biogeographers tend to be history oriented.”46Without necessarily rejecting MacArthur's explanation, my study suggests a more complex relationship between taxonomic and ecological plant geographies. At the turn of the century a group of botanists self-consciously defined a new area of botanical research. These ecologists defined their new discipline in opposition to what they believed was a moribund, nineteenth-century, natural-history tradition. They turned from historically oriented, descriptive, taxonomic plant geography to experimental physiology. The new ecological plant geography was to focus on communities rather than on species, on proximate environmental causes rather than on historical explanations, and on physiological experiments rather than on morphological descriptions.As we look back, much of the “revolt from morphology” was rhetorical. Ecologists never completely replaced species as units of distribution, nor did they set geography on an explicitly physiological basis. Indeed, much of early ecological research was, quite simply, descriptive. Plant communities were defined in terms of dominant species, representative life forms, or general physiognomy. The underlying physiological basis for community characteristics was more often assumed than demonstrated by experiments.Despite the fact that ecological plant geography was not a truly physiological specialty, it was significantly different from more traditional taxonomic plant geography. First, ecologists were less explicitly evolutionary in their approach than were taxonomists. Following Darwin, most taxonomic plant geographers viewed distribution in historical terms. In contrast, early ecologists tended to ignore the traditional geographic problems. Most ecologists were skeptical of historical explanations, emphasizing instead the proximate, environmental causes of distribution. While some nineteenth-century biogeographers had studied the correlation between climate and vegetation, twentieth-century ecologists focused much more sharply on the interactions between plant and environment. Plant ecologists did not place biogeography on a physiological basis, but by emphasizing physiology they laid the foundation for a more detailed understanding of adaption. This emphasis on physiology and environmental causation was a second distinguishing characteristic of ecological plant geography. Finally, the idea of the plant community, articulated by Eugenius Warming in 1895, provided ecologists with a unique perspective on the distribution of plants. For early ecologists, the community was more than an assemblage of species; it was an integrated unit. The distribution of these units became the major focus of ecological plant geography. Communities never completely replaced species as geographic units, and the distinction between flora and vegetation was often blurred. Nonetheless, ecologists were innovative in studying the distribution of structurally and functionally integrated groups of plants.In the twentieth century plant geography has occupied an anomalous position in biology. It has not developed into an autonomous discipline, nor has it been incorporated into the developing discipline of ecology. Ecologists and taxonomists have pursued fairly distinct styles of geographic research, with the result that two relatively independent approaches to the study of plant distribution have persisted. (shrink)

This article examines the changing status of tropical biology by considering the origins and early development of the Barro Colorado Island Biological Laboratory. Today the laboratory is part of a large diversified tropical research center operated by the Smithsonian Institution. However, for most of its history the laboratory led a tenuous existence. Both the early problems and eventual success of the institution can only be explained by considering the interaction of various intellectual, institutional, and broader social factors.