The eukaryote cell is one of the most radical innovations in the history of life, and the circumstances of its emergence are still deeply contested. This paper will outline the recent history of attempts to reveal these origins, with special attention to the argumentative strategies used to support claims about the first eukaryote cell. I will focus on two general models of eukaryogenesis: the phagotrophy model and the syntrophy model. As their labels indicate, they are based on claims about metabolic (...) relationships. The first foregrounds the ability to consume other organisms; the second the ability to enter into symbiotic metabolic arrangements. More importantly, however, the first model argues for the autogenous or self-generated origins of the eukaryote cell, and the second for its exogenous or externally generated origins. Framing cell evolution this way leads each model to assert different priorities in regard to cell-biological versus molecular evidence, cellular versus environmental influences, plausibility versus evolutionary probability, and irreducibility versus the continuity of cell types. My examination of these issues will conclude with broader reflections on the implications of eukaryogenesis studies for a philosophical understanding of scientific contestation. (shrink)

With historical hindsight, it can be little questioned that the view of protozoa as unicellular organisms was important for the development of the discipline of protozoology. In the early years of this century, the assumption of unicellularity provided a sound justification for the study of protists: it linked them to the metazoa and supported the claim that the study of these “simple” unicellular organisms could shed light on the organization of the metazoan cell. This prospect was significant, given the state (...) of cytology circa 1910. In the wake of the major gains made in understanding nuclear division in the last two decades of the nineteenth century, cytology was suddenly confronted with many, seemingly less penetrable, problems. Several aspects of nuclear organization still remained unexplained, and recent research had revealed the presence in the cytoplasm of structures whose functions in cell life were unknown. Classical methods of cytology, relying on descriptive, morphological analysis, seemed ill equipped to resolve these questions.Hertwig's program for protozoology, grounded in the assumption of the fundamental unity of organization in protozoa and metazoa, offered a potential means for investigating these and other problems of cell theory. Linked to mainstream cytology, protozoology was advocated as a means of experimentally investigating key biolobical processes — reproduction, metabolism, and organelle morphology and physiology — less accessible in higher organisms. Protozoa were hailed as prime experimental organisms, in which cell structure and function could be more easily studied. Unlike the metazoan cell, they could be subjected to controlled experiments in which the external environment was modified and the effects monitored. Protozoa offered, in other words, a promising experimental means by which to investigate the cell — its structures and its processes.The success of this program within Germany was soon apparent. In contrast to the rather neglected state of the discipline in 1900, protozoology began to be recognized as more than a somewhat obscure area of study for specialists. In practical terms, this translated into greater numbers of students attracted to the field, increased institutional support for the discipline, and its elevation in status within the biological sciences as new developments, particularly in connection with medical applications, began to draw attention to the field.64The unicellular hypothesis also promoted the internal development of the science. It provided a rationale for introducing the various techniques used in cytology, embryology, physiology, and the new field of biochemistry as suitable research tools for protozoology as well. This vastly extended the research possibilities and facilitated the understanding of, among other things, protozoan organization, modes of reproduction, and evolutionary relationships. The new experimental grounding of the discipline in turn fitted in well with developments in biology at large: in contrast to the descriptive methodology that had predominated in the nineteenth century, this new experimental program placed protozoology at the forefront of the early twentieth-century movement to make biology an experimental science comparable to physics and chemistry.Yet the criticism of the unicellular hypothesis can also be seen as having served a valuable function within the development of the discipline. It focused attention on the study of protists as organisms in their own right, not simply as models for metazoan cells. More generally, it helped to remind biologists of the particular evolutionary assumptions that supported this conception. Dobell and other British critics pointed out, among other things, the association between the theory of recapitulation and the interpretation of protozoa as unicellular organisms. At the time when the recapitulation theory and the germ-layer doctrine were in decline, it was important to stress how these evolutionary ideas also entered into the contemporary concepts of subsidiary specialties. This was as true for protozoology as it was for cell theory itself. The chromidial theory, in its various guises, and the binuclearity hypothesis did in fact contain elements of recapitulationist reasoning, and they were open to criticism for the same kind of overly speculative theorizing that characterized this evolution theory. Dobell's critique forced protozoologists and cell theorists alike to review the theoretical postulates guiding their investigations.In the absence of further historical studies, it is hard to evaluate the consequences of this debate in later years. The issue was not whether protozoa were the precursors of metazoa — both sides accepted this. They disagreed over which particular protozoon had served as the ancestral form, and this, in turn, influenced their stance on the question of unicellularity. The situation is little changed today. Because the former question is still an open one, the latter remains so too. Both of the models for the origin of multicellular organisms — colonies of ciliates versus multinucleate protists — are still presented as possible mechanisms in modern textbooks of evolution. Unable to judge the dispute in terms of the ultimate validity of the competing conceptions, the historian requires other criteria. It perhaps becomes more important to evaluate the issues in the context of the internal and external stimulus they provided the discipline.65 In these terms, and from the present historical vantage point, Hertwig's research program for protozoology, based upon the unicellular hypothesis, appears to have been a successful one. (shrink)

A historical and critical analysis of the concept of the gene that attempts to provide new perspectives and metaphors for the transformation of biology and its philosophy.

What is the relation between things and theories, the material world and its scientific representations? This is a staple philosophical problem that rarely counts as historically legitimate or fruitful. In the following dialogue, the interlocutors do not argue for or against realism. Instead, they explore changing relations between theories and things, between contested objects of knowledge and less contested, more everyday things. Widely seen as the life sciences' first general theory, the cell theory underwent dramatic changes during the nineteenth century. (...) The dialogue establishes that each successive version of the cell theory was formulated -- each identity of the object cell was formed -- around a different material : cork, cartilage, eggs in cleavage, muscle. Such things thus serve as exemplary materials, in ways not described by standard concepts like induction, theory -testing, theory -laden observation, and construction. Still, how can theories and perspective possibly be honed on things if these are apprehended differently by different observers according to their interests, training, culture, or indeed theories? The second part of the dialogue addresses this problem, partly through the verbal and visual schemata that were used by nineteenth-century microscopists and that are comparable to schemata in the visual arts. The third part of the dialogue considers the exemplary materials as a historical sequence, itself needing explanation. Theoretical change devolved partly from wider histories and geographies of the prevalence, availability, or scientific and cultural status of materials such as plants, animals, and muscle. (shrink)

The concept of mechanism in biology has three distinct meanings. It may refer to a philosophical thesis about the nature of life and biology (‘mechanicism’), to the internal workings of a machine-like structure (‘machine mechanism’), or to the causal explanation of a particular phenomenon (‘causal mechanism’). In this paper I trace the conceptual evolution of ‘mechanism’ in the history of biology, and I examine how the three meanings of this term have come to be featured in the philosophy of biology, (...) situating the new ‘mechanismic program’ in this context. I argue that the leading advocates of the mechanismic program (i.e., Craver, Darden, Bechtel, etc.) inadvertently conflate the different senses of ‘mechanism’. Specifically, they all inappropriately endow causal mechanisms with the ontic status of machine mechanisms, and this invariably results in problematic accounts of the role played by mechanism-talk in scientific practice. I suggest that for effective analyses of the concept of mechanism, causal mechanisms need to be distinguished from machine mechanisms, and the new mechanismic program in the philosophy of biology needs to be demarcated from the traditional concerns of mechanistic biology. (shrink)

Genesis: The Evolution of Biology presents a history of the past two centuries of biology, suitable for use in courses, but of interest more broadly to evolutionary biologists, geneticists, and biomedical scientists, as well as general readers interested in the history of science. The book covers the early evolutionary biologists-Lamarck, Cuvier, Darwin and Wallace through Mayr and the neodarwinian synthesis, in much the same way as other histories of evolution have done, bringing in also the social implications, the struggles with (...) our religious understanding, and the interweaving of genetics into evolutionary theory. What is novel about Sapp's account is a real integration of the cytological tradition, from Schwann, Boveri, and the other early cell biologists and embryologists, and the coverage of symbiosis, microbial evolutionary phylogenies, and the new understanding of the diversification of life coming from comparative analyses of complete microbial genomes. The book is a history of theories about evolution, genes and organisms from Lamarck and Darwin to the present day. This is the first book on the general history of evolutionary biology to include the history of research and theories about symbiosis in evolution, and first to include research on microbial evolution which were excluded from the classical neo-Darwinian synthesis. Bacterial evolution, and symbiosis in evolution are also excluded from virtually every book on the history of biology. (shrink)

Is life different from the non-living? If so, how? And how, in that case, does biology as the study of living things differ from other sciences? These questions are traced through an exploration of episodes in the history of biology and philosophy. The book begins with Aristotle, then moves on to Descartes, comparing his position with that of Harvey. In the eighteenth century the authors consider Buffon and Kant. In the nineteenth century the authors examine the Cuvier-Geoffroy debate, pre-Darwinian geology (...) and natural theology, Darwin and the transition from Darwin to the revival of Mendelism. Two chapters deal with the evolutionary synthesis and such questions as the species problem, the reducibility or otherwise of biology to physics and chemistry, and the problem of biological explanation in terms of function and teleology. The final chapters reflect on the implications of the philosophy of biology for philosophy of science in general. (shrink)

Thinking about Biology is intended for biology students who are interested in reflecting on the wider contexts of their studies. This 2003 book encourages students to see that biology does not deliver certainties; it discusses how biological ideas become established facts; it uses history to examine how ideas change, and to show that the biological facts that form the basis of a biology course are likely to change too. Each chapter is based on biological topics, and examines them for their (...) philosophical, social and political implications. Topics covered include the role of natural selection in evolution, the history of ideas about fertilisation and inheritance, vivisection, and reductionism. Genetically modified foods, xenotransplantation, eugenics, and genetic testing are some of the controversial subjects discussed. Thinking About Biology should be essential reading for all college students already taking a biology course, and for those contemplating such a course in the future. (shrink)

The cell theory—the thesis that all life is made up of one or more cells, the fundamental structural and physiological unit—is one of the most celebrated achievements of modern biological science. And yet from its very inception in the nineteenth century it has faced repeated criticism from some biologists. Why do some continue to criticize the cell theory, and how has it managed nevertheless to keep burying its undertakers? The answers to these questions reveal the complex nature of the cell (...) theory and the cell concept on which it is based. Like other scientific ‘laws’, the assertion that all living things are made of cells purchases its universality at the expense of abstraction. If, however, this law is regarded merely as a widely applicable empirical generalization with notable exceptions, it still remains too important to discard. Debate about whether the cell or the organism standpoint provides the more correct account of anatomical, physiological, and developmental facts illustrates the tension between our attempts to express the truth about reality in conceptual terms conducive to a unified human understanding. (shrink)