The term ‘mechanism’ has been used in two quite different ways in the history of biology. Operative, or explanatory mechanism refers to the step-by-step description or explanation of how components in a system interact to yield a particular outcome . Philosophical Mechanism, on the other hand, refers to a broad view of organisms as material entities, functioning in ways similar to machines — that is, carrying out a variety of activities based on known chemical and physical processes. In the early (...) twentieth century philosophical Mechanism became the foundation of a ‘new biology’ that sought to establish the life sciences on the same solid and rigorous foundation as the physical sciences, including a strong emphasis on experimentation. In the context of the times this campaign was particularly aimed at combating the reintroduction of more holistic, non-mechanical approaches into the life sciences . In so doing, Mechanists failed to see some of the strong points of non-vitalistic holistic thinking. The two approaches are illustrated in the work of Jacques Loeb and Hans Spemann. (shrink)

De Vries' mutation theory has not stood the test of time. The supposed mutations of Oenothera were in reality complex recombination phenomena, ultimately explicable in Mendelian terms, while instances of large-scale mutations were found wanting in other species. By 1915 the mutation theory had begun to lose its grip on the biological community; by de Vries' death in 1935 it was almost completely abandoned. Yet, as we have seen, during the first decade of the present century it achieved an enormous (...) popularity. As this paper has tried to suggest, one of the principal reasons for this was that de Vries' theory served as a banner around which a whole crowd of disaffected Darwinians or anti-Darwinians could rally. However, not all of those who favored de Vries did so for quite the same reasons. Underlying the multitude of views ran several common threads: a dissatisfaction with current Darwinian theory born out of misunderstanding natural selection, a general misunderstanding of the nature of species, and a prejudice against speculative, nontestable theories in biology.Supporters of de Vries were not the only opponents of Darwinism, nor was the mutation theory the only alternative to natural selection. In the early twentieth century a number of theories had been proposed to explain away the problems which Darwin had left unsolved. There was the idea of orthogenesis, championed by the American paleontologists Cope, Osborn and others; organic selection (or orthoplasy) was championed by M. M. Baldwin and C. Lloyd Morgan; there were the concepts of convergent evolution proposed by Hermann Friedmann, the theory of physiological selection by John George Romanes, and the concepts of reproductive divergence by H. M. Vernon. Virtually none of these men either accepted or were strong supporters of the de Vriesian theory, for each had his own particular ‘ism” to advocate as the major factor in evolution. The existence of a large number of such theories, each purporting to be the explanation, was characteristic of evolutionary theory at the turn of the century. It is to a large extent the emphasis on such fragmentary concepts that retarded development of the comprehensive theory of evolution which emerged in the 1920's and 1930's. For the historian, however, a study of these alternative theories is instructive in trying to understand the inherent difficulties which Dawwinian theory posed to biologists at the time. De Vries' mutation theory serves historically as a mirror to reflect the critical mood of a generation hostile to the theory of natural selection.It has often been claimed that it was impossible to understand the mechanism of natural selection until it could be placed in genetic and mathematical terms. It is certainly true that great strides have been made in population genetics and the treatment of evolutionary concepts with mathematical tools in the last forty years. But the very people who developed the genetical and mathematical approach to evolution were already convinced of the essential correctness of Darwinian theory before they started. Advances in an understanding of Mendelian heredity aided greatly in solving one important issue for evolutionists: the origin of variations. And the rigor with which selection acted could best be studied by observing changes in gene frequencies (calculated mathematically) over a number of generations. But as this paper has shown, two of the basic problems which biologists faced in evaluating Darwinian theory at the turn of the century-the nature of species, and the criteria of what constituted an acceptable explanation in biological science-could not be answered directly by mathematics. What mathematical and genetical theory did do was to help convince the skeptics of the validity of the Darwinian proposition.The change in explanatory criteria which many hailed as de Vries' most important contribution to evolutionary theory seems to have been part of a general emergence of twentieth-century biology from the domination of theorizers in the nineteenth. It also marked the emergence of America from the domination of biological, and particularly evolutionary, influence of Europeans. The change occurred in three areas: in the kinds of questions asked: testable versus non-testable; in the kind of data sought: quantitative versus qualitative; and in the kinds of theories proposed: analytical and reductive—the attempt to see complex processes in terms of simpler components-as opposed to synthetic and speculative. Although ultimately wrong in his idea, de Vries and his theories rode high on the wave of “experimentalism” which was the harbinger of a new era in evolutionary theory. (shrink)

We may now ask the question: In what historical perspective should we place the work of Richard Goldschmidt? There is no doubt that in the period 1910–1950 Goldschmidt was an important and prolific figure in the history of biology in general, and of genetics in particular. His textbook on physiological genetics, published in 1938, was an amazing compendium of ideas put forward in the previous half-century about how genes influence physiology and development. His earlier studies on the genetic and geographic (...) distribution of the various species and races of Lymantria contributed soundly to an understanding of the inheritance and development of sex, as well as the genetics of speciation. He was a curious mixture of the experimentalist, empiricist, and theorizer, who could grasp both the large and the small at once and wrap them into the same integrated and coherent package.In insisting on trying to relate genetics to development, Goldschmidt was continually forced to speculate and to forsake experimental fact for generalized theory. In refusing to reconcile a physiological and developmental conception with a corpuscular theory of the gene, he forced himself to substitute for a large body of experimentally verified evidence, vague and general speculations which did not lead in any precise direction. L. C. Dunn summarizes succinctly the effect of Goldschmidt's thinking on the development of genetic theory: Although Goldschmidt's ideas had a considerable influence in directing attention to the developmental processes intervening between genes and characters, they did not lead to the establishment of a general theory of development in genetical terms. In fact, at the end of the period, as signalized by Goldschmidt's book of 1938 [Physiological Gentics] doubt remained whether there was a field with a defined problem which could be identified as developmental genetics.Yet the frequency with which Goldschmidt is cited by later writers suggests that there is a more positive side to his contribution than this. The early Mendelians had recognized the genic constitution of organisms and the Drosophila workers had uncovered in detail the chromosomal mechanism of heredity. These great discoveries were of classical character, solidly based on a multitude of well established facts. By themselves, however, they would not have been sufficient to place genetics in the central position within biology which it was to assume. Beyond the “static” analysis of gene transmission an insight was needed into the dynamic role of genes in cellular physiology, biochemistry, and development. Goldschmidt recognized this aspect and outlined in brilliant generalizations a physiological theory of genetics. Necessarily the prophetic nature of this achievement — romantic in the sense of Ostwald's classification of great scientists and their discoveries — transcended its factual basis. It was the audacity of the theoretician unimpeded by the still scanty data which gave a new focus to biological thought.Some have called Goldschmidt an “obstructionist” in the history of genetics—one whose efforts were largely directed toward useless and continual criticism — challenge for the sake of challenge. As this line of argument goes, time wasted answering Goldschmidt's poorly conceived criticisms could have been better used to pursue new lines of thought within the classical gene theory. Sometimes historians are upbraided for studying the work of such “obstructionists,” or even the work of those whose ideas have later proved to be inadequate. This argument misses the point of history and the lessons which it can teach. Perhaps Goldschmidt did take the time of a number of the classical geneticists who tried to answer his objections to the gene theory; and perhaps many of his own ideas about genes were, by today's view, “wrong.” These are always easier judgments to make by hindsight than at the moment. But that is not the point. Goldschmidt had a considerable influence on his contemporaries, and to dismiss him as an obstructionist because his opponents later proved to be more nearly right, distorts history and obscures significant questions which we might well be asking. It might be valuable to know why Goldschmidt felt compelled to be an iconoclast —and how that impulse, psychological in orgin, led him to overlook critical items of evidence which his opponents considered more carefully. It might also be valuable to try and understand how a contemporary of Goldschmidt or. Morgan really viewed the gene theory — what were its strong and weak point? Such questions are not readily answered by studying the work of only those men who were correct by later standards.Answers to some of the above questions can be gleaned from this study of Goldschmidt — though the first, and most psychologically oriented, question is largely untouched here.On the one hand, Goldschmidt forced classical geneticists to reexamine the foundation of their ideas about the nature, inviolability, and even physical dimensions of genes. He also kept alive the very real problems of gene physiology and its relations to development — a relationship that was given less attention by the Drosophila school in their pursuit of the transmission process. On a broader level he emphasized to the biological community a principle that was in danger of being lost in the enthusiasm surrounding the expansion of the Mendelian-chromosome theory. The point was that all theories in science are transient, logical constructs which should not be held as sacred. Time and again, as the history of science has shown, theories become rigid structures which retard new modes of thought. From Goldschmidt's perspective, the gene theory was in danger of performing just that function, for it was preventing workers from viewing the gene in a functional as well as a structural light.On the other hand, examining the work of critics (or even of outright “obstructionists”) gives the historian an opportunity to observe how the more established community of scholars at some point in time reacts to challenges of its cherished ideas. The fact that many workers in his own day (such as Beadle, Luria, Delbruck, Sturtevant, Bridges, and others), as well as most geneticists today, saw Goldschmidt as having been largely “obstructionist” is useful historical (and/or sociological) data. Clearly, as this paper has tried to show, Goldschmidt's ideas were not all obstructionist, and his viewpoint that genes must be considered functionally was one which was clearly valid, premature as it may have been from an experimental and technique point of view. Perhaps Goldschmidt's major fault was that he developed alternative theories which were not easily testable. Nonetheless, his challenge to a fundamental and established idea brought forth a reaction from many members of the genetic community which indicates how unwilling they were to reconsider the formalized theory on which their work was based. While many of Goldschmidt's criticisms — and particularly his way of making them — arose out of his own idiosyncrasies, they were also a product of his times. His view of the nature of theory-construction, and his rejection of old-style reductionism and mechanism, were part of a growing awareness within the world scientific community that explanations based on reducing complex phenomena to ultimate particles or units were clearly inadequate. The success of the Mendelian-chromosome theory had obscured that fact for many geneticists, but to Goldschmidt it was a point that could not be allowed to pass unnoticed. (shrink)

Viktor Hamburger was a developmental biologist interested in the ontogenesis of the vertebrate nervous system. A student of Hans Spemann at Freiburg in the 1920s, Hamburger picked up a holistic view of the embryo that precluded him from treating it in a reductionist way; at the same time, he was committed to a materialist and analytical approach that eschewed any form of vitalism or metaphysics. This paper explores how Hamburger walked this thin line between mechanistic reductionism and metaphysical vitalism in (...) light of his work on the factors influencing growth of neurons into limb buds, and the discovery of nerve growth factor, work carried out with Rita Levi-Montalcini and Stanley Cohen. (shrink)

This book highlights not only aspects of the career of Everett Mendelsohn, one of the premier historians of biology of our age, but also a wide range of topics that are now grouped under the general heading of science studies. This broad collection includes articles on the relations between science and the military, science as narrative, natural history and conservation, Marxism and science, the Human Genome Project, and the relation of philosophy to the study of embryonic development in the 18th (...) century. This book is essential not only for those who admire Professor Mendelsohn's work but also for those who want a slice of the current field of science studies. Audience: The main readership of this volume consists of historians of science, technology, and medicine, and sociologists of science. The book will also appeal to philosophers of science and biologists. Those interested in Middle Eastern studies will find the discussion of Professor Mendelsohn's political work in this area, as well as the article dealing with his activism in general, of considerable interest. (shrink)