August Weismann is famous for having argued against the inheritance of acquired characters. However, an analysis of his work indicates that Weismann always held that changes in external conditions, acting during development, were the necessary causes of variation in the hereditary material. For much of his career he held that acquired germ-plasm variation was inherited. An irony, which is in tension with much of the standard twentieth-century history of biology, thus exists – Weismann was not a Weismannian. I distinguish three (...) claims regarding the germ-plasm: (1) its continuity, (2) its morphological sequestration, and (3) its variational sequestration. With respect to changes in Weismann’s views on the cause of variation, I divide his career into four stages. For each stage I analyze his beliefs on the relative importance of changes in external conditions and sexual reproduction as causes of variation in the hereditary material. Weismann believed, and Weismannism denies, that variation, heredity, and development were deeply intertwined processes. This article is part of a larger project comparing commitments regarding variation during the latter half of the nineteenth century. (shrink)

Darwin’s classic ‘Origin of Species’ (Darwin 1859) described forces of selection acting upon individuals, but there remains a great deal of controversy about what exactly the status and definition of a biological individual is. Recently some authors have argued that the individual is dispensable – that an inability to pin it down is not problematic because little rests on it anyway. The aim of this paper is to show that there is a real problem of biological individuality, and an urgent (...) need to arbitrate over the current plethora of solutions to it. (shrink)

One central tenet of the Modern Evolutionary Synthesis , and the consensus view among biologists until now, is that all genetic mutations occur by “chance” or at “random” with respect to adaptation. However, the discovery of some molecular mechanisms enhancing mutation rate in response to environmental conditions has given rise to discussions among biologists, historians and philosophers of biology about the “chance” vs “directed” character of mutations . In fact, some argue that mutations due to a particular kind of mutator (...) mechanisms challenge the Modern Synthesis because they are produced when and where needed by the organisms concerned. This paper provides a defense of the Modern Synthesis’ consensus view about the chance nature of all genetic mutations by reacting to Jablonka and Lamb’s analysis of genetic mutations and the explicit Lamarckian flavor of their arguments. I argue that biologists can continue to talk about chance mutations according to what I call and define as the notion of “evolutionary chance,” which I claim is the Modern Synthesis’ consensus view and a reformulation of Darwin’s most influential idea of “chance” variation. Advances in molecular genetics are therefore significant but not revolutionary with respect to the Modern Synthesis’ paradigm. (shrink)

The highly structured mechanisms of cancers, their tendency to occur as a response to environmental stress, and the existence of oncogenes, suggest that neoplasticity may represent more than a biological disfunction. It is proposed that cancer exists as a phylogenetic mechanism serving to promote hyperevolution, albeit at the expense of the ontogeny, that is similar to a process recently discovered in bacterial mutations. Cell-surface-associated nucleic acid in tumorigenic cells and sperm cell vectorization of foreign DNA indicate the existence of essential (...) mechanisms necessary to the occurrence of cancer mediated hyperevolution. An analysis of the proposed mechanism indicates that for mutagenesis of chemical cytology, stress induced neoplasticity confers an evolutionary advantage of more than two orders of magnitude. (shrink)

This paper analyzes the generation and function of hitherto ignored or misrepresented interfield theories , theories which bridge two fields of science. Interfield theories are likely to be generated when two fields share an interest in explaining different aspects of the same phenomenon and when background knowledge already exists relating the two fields. The interfield theory functions to provide a solution to a characteristic type of theoretical problem: how are the relations between fields to be explained? In solving this problem (...) the interfield theory may provide answers to questions which arise in one field but cannot be answered within it alone, may focus attention on domain items not previously considered important, and may predict new domain items for one or both fields. Implications of this analysis for the problems of reduction and the unity and progress of science are mentioned. (shrink)

Studies that compare human and animal behaviour suspend prejudices about mind, body and their relation, by approaching thinking in terms of behaviour. Yet comparative approaches typically engage another prejudice, motivated by human social and bodily experience: taking the lone animal as the unit of comparison. This prejudice informs Heidegger’s and Merleau-Ponty’s comparative studies, and conceals something important: that animals moving as a group in an environment can develop new sorts of “sense.” The study of animal group-life suggests a new way (...) of thinking about the creation of sense, about the body, the brain, and the relation between thinking and nature. (shrink)

Conscious Agency is a major driver of evolution. Artificial Selection (i.e. Conscious Selection by human breeders) was the foil against which Charles Darwin defined Natural Selection. In later work, he extended Artificial Selection to other species. That ability for social (e.g. sexual) selection must have evolved. Jablonka and Ginsburg identify markers of conscious agency, such as Unlimited Associative Learning (UAL), and show that it must have existed at the time of the Cambrian Explosion. To their insights, my commentary argues that (...) the harnessing of stochasticity was also involved in the evolution of the faculty of choice in organisms. (shrink)

The ‘Major Transitions in Evolution’ framework has emerged as the dominant paradigm for understanding the origins of life's hierarchical organization, but it has been criticized on the grounds that it lacks theoretical unity, that is, that the events included in the framework do not constitute a coherent category. I agree with this criticism, and I argue that the best response is to modify the framework so that the events it includes do comprise a coherent category, one whose members share fundamental (...) similarities. Specifically, I recommend defining major transitions as all those, and only those, events and processes that result in the emergence of a new population of evolutionary individuals. Two sorts of change will be required to achieve this. First, events and processes that do not meet this criterion, such as the origins of the genetic code and of human language, should be excluded. Second, events and processes that do meet the criterion, but which have generally been neglected, should be included. These changes would have the dual benefits of making MTEs a philosophically coherent category and of increasing the sample size on which we may infer trends and general principles that may apply to all MTEs. (shrink)

In this work I propose a theory of evolution as a process of unfolding. This theory is based on four logically concatenated principles. The principle of evolutionary order establishes that the more complex cannot be generated from the simpler. The principle of origin establishes that there must be a maximum complexity that originates the others by logical deduction. Finally, the principle of unfolding and the principle of actualization guarantee the development of the evolutionary process from the simplest to the most (...) complex. These logical principles determine the existence of a virtual ideological matrix that contains the sequence of the preformed and folded morphogenetic fields. In this manner, the evolutionary process consists of the sequential unfolding and actualization of these fields, which is motorized by a process of teleologization carried out by the opening consciousness of the forms included in the fields of the ideological matrix. This theory leads to a radical change of perspective regarding the materialist worldview, and places life at the center of the evolutionary process as an activity carried out by a consciousness that seeks to fulfill a purpose by actualizing its own potentialities. (shrink)

According to neo-Aristotelian ethical naturalism, moral goodness is an instance of natural goodness, a kind of normativity supposedly already present in nature in the biological realm of non-human living things. Proponents of this view appeal to Michael Thompson’s conception of a life-form--the form of a living organism--to give an account of natural goodness. However, although neo-Aristotelians call themselves naturalists, they hardly ever consult the science of biology to defend their commitments regarding biological organisms. This has led many critics to argue (...) that the neo-Aristotelian account of natural normativity is out of touch with the findings of modern evolutionary biology. One line of response to this objection, presented by John Hacker-Wright and Micah Lott, claims that the neo-Aristotelian concept of a living organism has to be presupposed in evolutionary biology as long as organisms are the subjects of evolutionary explanation. In this paper, I examine this response by tracing the concept of organism in modern evolutionary biology. I first argue that the Modern Synthesis theory of evolution, which understands evolution as change in gene frequencies within a population, does not presuppose the relevant concept of organism. I then explore an alternative view of evolution that has emerged in the past twenty years from advances in evolutionary developmental biology. I argue that this so called ‘evo-devo’ approach makes room for an explanatory concept of organism that can be reconciled with the neo-Aristotelian view. Moreover, I argue that although the explanatory role of the concept of organism in evolutionary biology is still contentious, the well-established role of this concept in developmental biology can be used to defend the biological commitments of neo-Aristotelian naturalism. (shrink)

The so-called “Baldwin Effect” has been studied for years in the fields of Artificial Life, Cognitive Science, and Evolutionary Theory across disciplines. This idea is often conflated with genetic assimilation, and has raised controversy in trans-disciplinary scientific discourse due to the many interpretations it has. This paper revisits the “Baldwin Effect” in Baldwin’s original spirit from a joint historical, theoretical and experimental approach. Social Heredity – the inheritance of cultural knowledge via non-genetic means in Baldwin’s term – is also taken (...) into consideration. I shall argue that the Baldwin Effect can occur via social heredity without necessity for genetic assimilation. Computational experiments are carried out to show that when social heredity is permitted with high fidelity, there is no need for the assimilation of acquired characteristics; instead the Baldwin Effect occurs as promoting more plasticity to facilitate future intelligence. The role of mind and intelligence in evolution and its implications in an extended synthesis of evolution are briefly discussed. (shrink)

The increasing attention which has been given to social history of science and to the sociological analysis of scientific activity has resulted in a renewed interest in scientific controversies. Furthermore, the rejection of the presentist view of history, according to which those contestants who took what we can identify, with the benefit of modern knowledge, as the ‘right’ stand in a controversy, were right and their opponents were ‘wrong’, left the subject of scientific controversies with many questions. What determines their (...) emergence, course and resolution? When Froggatt and Nevin wrote on the Bio-metric-Mendelian controversy in 1971 they called their article ‘descriptive rather than interpretative’, so they avoided the very questions we would like to ask. Provine, in the same year, concentrated on the strong personalities of the contestants, their clashes, and the scientific arguments in play. But in 1975 Mackenzie and Barnes argued that the controversy could not be accounted for unless recourse was had to sociological factors. Their view has become widely known and figured prominently in 1982 in Steven Shapin's recital of the empirical achievements of the application of the sociological approach. I have returned to this subject because I do not yet feel altogether convinced by Mackenzie and Barnes' analysis. Even if their analysis of the controversy between Pearson and Bateson be accepted, it is not so obvious how effectively it can be used to explain the controversy between Weldon and Bateson, and I am not confident that it is adequate for an understanding of the evolution of their differing views of the mechanism of evolution. (shrink)

The concept of adaptation is employed in many fields such as biology, psychology, cognitive sciences, robotics, social sciences, even literacy and art,1 and its meaning varies quite evidently according to the particular research context in which it is applied. We expect to find a particularly rich catalogue of meanings within evolutionary biology, where adaptation has held a particularly central role since Darwin’s The Origin of Species (1859) throughout important epistemological shifts and scientific findings that enriched and diversified the concept. Accordingly, (...) a conceptual taxonomy of adaptation in evolutionary biology may help to disambiguate it. Interdisciplinary researches focused on adaptation would benefit from such a result. In the present work we recognize and define seven different meanings of adaptation: (1) individual fitness; (2) adaptation of a population; (3) adaptation as the process of natural selection; (4) adaptive traits; (5) molecular adaptation; (6) adaptation as structural tinkering; (7) plasticity. For convenience here, we refer to them as W-, P-, NS-, T-, M-, S- and PL-ADAPTATION. We present the seven meanings in some detail, hinting at their respective origins and conceptual developments in the history of evolutionary thought (references are offered for further deepening). However, it is important to point out that evolution researchers seldom if ever refer to a single meaning purified from the others. This applies also to the authors we cite as representatives of one of the seven meanings. In Discussion and Conclusion draw from our work some future perspectives for adaptation within evolutionary biology. (shrink)

This article presents a reconstruction of the so-called classical, formal or Mendelian genetics, which is intended to be more complete and adequate than existing reconstructions. This reconstruction has been carried out with the instruments, duly modified and extended with respect to the case under consideration, of the structuralist conception of theories. The so-called Mendel’s Laws, as well as linkage genetics and gene mapping are formulated in a precise manner while the global structure of genetics is represented as a theory-net. These (...) results are of methodological, philosophical and didactical relevance. (shrink)

The ArgumentThis paper argues that different epistemic styles exist in science, and that these make up an important unit of analysis for studying science. On occasion these different sets of commitments to ways of doing and knowing about the world may fall along national boundaries. The case presented here examines German and American embryology around 1900 and shows that differences in goals and approaches make up different epistemic styles.In particular, the Germans sought causal mechanical explanations of as many phenomena as (...) possible, guided by strong theories which achieved confirmation when they fit with as much of the available data as possible. The Americans, in contrast, sought definitive facts, as many as possible, which might be quite specific or narrowly based. These facts could lead to empirical generalizations which, in turn, could guide the generation of new knowledge in the form of new facts. Thus, the two epistemic styles emphasized different goals, processes of investigation, and standards of evidence. (shrink)

Exact sciences are described as sciences whose theories are formalized. These are contrasted to inexact sciences, whose theories are not formalized. Formalization is described as a broader category than mathematization, involving any form/content distinction allowing forms, e.g., as represented in theoretical models, to be studied independently of the empirical content of a subject-matter domain. Exactness is a practice depending on the use of theories to control subject-matter domains and to align theoretical with empirical models and not merely a state of (...) a science. Inexact biological sciences tolerate a degree of “mismatch” between theoretical and empirical models and concepts. Three illustrations from biological sciences are discussed in which formalization is achieved by various means: Mendelism, Weismannism, and Darwinism. Frege’s idea of a “conceptual notation” is used to further characterize the notion of a form/content distinction. (shrink)

First the ‘Weismann barrier’ and later on Francis Crick’s ‘central dogma’ of molecular biology nourished the gene-centric paradigm of life, i.e., the conception of the gene/genome as a ‘central source’ from which hereditary specificity unidirectionally flows or radiates into cellular biochemistry and development. Today, due to advances in molecular genetics and epigenetics, such as the discovery of complex post-genomic and epigenetic processes in which genes are causally integrated, many theorists argue that a gene-centric conception of the organism has become problematic. (...) Here, we first explore the causal implications of the following two central dogma-related issues: (1) widespread reverse transcription—arguing for an extension from ‘DNA-genome’ to RNA-encompassing ‘NA-genome’ and, thus, from traditional DNA-centrism to a broader ‘NA-centrism’; and (2) the absence of a mechanism of reverse translation—arguing for the ‘structural primacy’ of NA-sequence over protein in cellular biochemistry. Secondly, we explore whether this latter conclusion can be extended to a ‘functional primacy’ of NA-sequence over protein in cellular biochemistry, which would imply a limited kind of ‘gene/NA-centrism’ confined to the subcellular level of NA/protein-based biochemistry. Finally, we explore the conditions—and their (non)fulfilment—for a more generalised form of gene-centrism extendable to higher levels of biological organisation. We conclude that the higher we go in the biological hierarchy, the more dubious gene-centric claims become. (shrink)

Evo-Devo exhibits a plurality of scientific “cultures” of practice and theory. When are the cultures acting—individually or collectively—in ways that actually move research forward, empirically, theoretically, and ethically? When do they become imperialistic, in the sense of excluding and subordinating other cultures? This chapter identifies six cultures – three /styles/ (mathematical modeling, mechanism, and history) and three /paradigms/ (adaptationism, structuralism, and cladism). The key assumptions standing behind, under, or within each of these cultures are explored. Characterizing the internal structure of (...) the cultures is necessary for understanding how they collaborate or compete, and how they are fragmented or integrated, in the rich interdisciplinary /trading zone/ (Galison 1997) of Evo-Devo. Evo-Devo is an important example of how science can progress through a radical plurality of perspectives and cultures. (shrink)

In the period 1875-1920, a debate about the generality and applicability of evolutionary theory to all organisms was motivated by work on unicellular ciliates like Paramecium because of their peculiar nuclear dualism and life cycles. The French cytologist Emile Maupas and the German zoologist August Weismann argued in the 1880s about the evolutionary origins and functions of sex (which in the ciliates is not linked to reproduction), and death (which appeared to be the inevitable fate of lineages denied sexual conjugation), (...) an argument rooted in the question of whether the ciliates and their processes where homologous to other cellular organisms. In the beginning of the twentieth century, this question of homology came to be less important as the ciliates were used by the British protozoologist Clifford Dobell and the American zoologist Herbert Spencer Jennings to study evolutionary processes in general rather than problems of development and cytology. For them, homology mattered less than analogy. This story illustrates two partially distinct problems in evolutionary biology: first, the question of whether all living things have common features and origins; and second, whether their history and current nature can be described by identical mechanisms. Where Maupas (contra Weismann) made the ciliates qualitatively the same as all other organisms in order to create a cohesive evolutionary theory for biology, Jennings and Dobell made them qualitatively different in order to achieve the same end. (shrink)

In responding to three reviews of Evolution in Four Dimensions (Jablonka and Lamb, 2005, MIT Press), we briefly consider the historical background to the present genecentred view of evolution, especially the way in which Weismann’s theories have influenced it, and discuss the origins of the notion of epigenetic inheritance. We reaffirm our belief that all types of hereditary information—genetic, epigenetic, behavioural and cultural—have contributed to evolutionary change, and outline recent evidence, mainly from epigenetic studies, that suggests that non-DNA heritable variations (...) are not rare and can be quite stable. We describe ways in which such variations may have influenced evolution. The approach we take leads to broader definitions of terms such as ‘units of heredity’, ‘units of evolution’, and ‘units of selection’, and we maintain that ‘information’ can be a useful concept if it is defined in terms of its effects on the receiver. Although we agree that evolutionary theory is not undergoing a Kuhnian revolution, the incorporation of new data and ideas about hereditary variation, and about the role of development in generating it, is leading to a version of Darwinism that is very different from the gene-centred one that dominated evolutionary thinking in the second half of the twentieth century. (shrink)

Samuel Butler is usually remembered for Erewhon, widely considered among the best English satires. He also contributed to philosophical biology in works that collectively compose the nineteenth century's finest statement of the evolutionary argument associated with the name of Lamarck. In writing on evolution, Butler was not presenting science for a popular audience but deliberately intervening in the scientific argument about Darwinism. Surprised by the success of his first venture in philosophical biology, Life and Habit, Butler committed himself to the (...) project of developing an alternative to Darwinism, which he did in three additional volumes, and these are the works canvassed in this “delayed book review.”. (shrink)

This is an epistemologically-driven history of the concept of evolution. Starting from its inception, this work will follow the development of this pregnant concept. However, in contradistinction to previous attempts, the objective will not be the identification of the different meanings it adopted through history, but conversely, it will let the concept to be unfolded, to be explicated and to express its own inner potentialities. The underlying thesis of the present work is, therefore, that the path that leads to the (...) development of the concept of evolution is the path that studies the possibilities of the evolution of concepts, and that the historical reconstruction of its conceptual trajectory will shed light into potential and unexploited possibilities. This methodology will provide useful tools and resources for future developments of the concept. For example, it will define the concept of transmutation as a different conceptual trajectory deviating from the one corresponding to evolution, at the onset of the 19th century. Moreover, epigenesis will not be the opposing concept to evolution, but only to simultaneous and instantaneous generation. It will demonstrate that every important system of epigenesis drew upon some kind of formative power to explain development. More importantly, it will show that the problem of preformation cannot be overlooked, and that some kind of virtual preformation must be considered in order to address the problems of generation and development. (shrink)

The British biologist, philosopher, and psychologist Conwy Lloyd Morgan is widely regarded as one of the founders of comparative psychology. He is especially well known for his eponymous canon, which aimed to provide a rule for the interpretation of mind from behavior. Emphasizing the importance of the context in which Morgan was working—one in which casual observations of animal behavior could be found in Nature magazine every week and psychology itself was fighting for scientific legitimacy—I provide an account of Morgan’s (...) vision for the comparative psychologist qua professional psychologist. To this end, I explore the important connection between Morgan and the evolutionary theorist, philosopher, and psychologist Herbert Spencer. It is from Spencer, I contend, that Morgan inherited a number of his key epistemological and methodological concerns about the nascent science of comparative psychology. This extends all the way to the canon, which only works as intended when paired with a Spencerian understanding of mental evolution as a progressive linear sequence. Far from being an incidental residue of a pre-Darwinian time, hierarchy was intentionally built into the very core of Morgan’s scientific comparative psychology. (shrink)

Advocates of an ‘extended evolutionary synthesis’ have claimed that standard evolutionary theory fails to accommodate epigenetic inheritance. The opponents of the extended synthesis argue that the evidence for epigenetic inheritance causing adaptive evolution in nature is insufficient. We suggest that the ambiguity surrounding the conception of the gene represents a background semantic issue in the debate. Starting from Haig’s gene-selectionist framework and Griffiths and Neumann-Held’s notion of the evolutionary gene, we define senses of ‘gene’, ‘environment’, and ‘phenotype’ in a way (...) that makes them consistent with gene-centric evolutionary theory. We argue that the evolutionary gene, when being materialized, need not be restricted to nucleic acids but can encompass other heritable units such as epialleles. If the evolutionary gene is understood more broadly, and the notions of environment and phenotype are defined accordingly, current evolutionary theory does not require a major conceptual change in order to incorporate the mechanisms of epigenetic inheritance. _1_ Introduction _2_ The Gene-centric Evolutionary Theory and the ‘Evolutionary Gene’ _2.1_ The evolutionary gene _2.2_ Genes, phenotypes, and environments _3_ Epigenetic Inheritance and the Gene-Centred Framework _3.1_ Treating the gene as the sole heritable material? _3.2_ Epigenetics and phenotypic plasticity _4_ Conclusion. (shrink)

Yes, fitness is the central concept of evolutionary biology, but it is an elusive concept. Almost everyone who looks at it seriously comes out in a different place.

This paper has three principal aims: first, through a detailed analysis of the hypotheses and assumptions underlying Weismann’s and Morgan’s disagreement on the nature of animal regeneration, it seeks to readdress the imbalance in coverage of their discussion, providing, at the same time, a fascinating case-study for those interested in general issues related to controversies in science. Second, contrary to Morgan’s beliefs according to which Weismann employed a speculative and unempirical method of scientific investigation, the article shows that Weismann performed (...) experiments, made observations and proposed ‘undogmatic’ theories open to refutation. Third, through the reconstruction of Weismann’s and Morgan’s disagreement, this study illustrates how biology, during the very late nineteenth and early twentieth centuries, was undergoing important changes. I argue that this controversy clearly and convincingly demonstrates how some important epistemic assumptions became increasingly problematic for some members of the younger generations of biologists. At the end of my discussion I will also argue that Weismann and Morgan both had strong well-grounded arguments supporting their conclusions; for this reason I suggest a few factors (“taken-for-granted” beliefs or assumptions) that could explain why their disagreement was doomed to remain unresolved. In particular, I will analyze their diverse explicative interests, their different theoretical concerns and their distinct use of the available evidence. (shrink)

The concept of natural kind is center stage in the debates about scientific realism. Champions of scientific realism such as Richard Boyd hold that our most developed scientific theories allow us to “cut the world at its joints” (Boyd, 1981, 1984, 1991). In the long run we can disclose natural kinds as nature made them, though as science progresses improvements in theory allow us to revise the extension of natural kind terms.

In 1920, Eugen Steinach and Paul Kammerer reported experiments showing that exposure to high temperatures altered the structure of the gonad and produced hyper-sexuality in "heat rats," presumably as a result of the increased production of sex hormones. Using Steinach's evidence that the gonad is a double gland with distinct sexual and generative functions, they used their findings to explain "racial" differences in the sexuality of indigenous tropical peoples and Europeans. The authors also reported that heat induced anatomical changes in (...) the interstitial cells of the gonad were inherited by the heat rats' descendants. Kammerer used this finding to link endocrinology to his long-standing interest in the inheritance of acquired characteristics. The heat rats supported his hypothesis that the interstitial cells of the double gland were the mechanism of somatic induction in the inheritance of acquired characteristics. The Steinach-Kammerer collaboration, Kammerer's use of Steinach's "puberty gland" to explain somatic induction, and his endocrine analysis of symbiosis reveal Paul Kammerer's late career attempt to integrate endocrinology and genetics with the political ideals of Austrian socialism. With them he developed a bioethics that challenged the growing reliance on race in eugenics and instead promoted cooperation over competition in evolution. I relate his attempt to the controversies surrounding the interstitial cells, to the status of extra-nuclear theories of heredity, and to Kammerer's commitment to Austromarxist social reforms during the interwar period. (shrink)

This volume, The Brazilian Studies in the Philosophy and History of Science, is the first attempt to present to a general audience, works from Brazil on this subject. The included papers are original, covering a remarkable number of relevant topics of philosophy of science, logic and on the history of science. The Brazilian community has increased in the last years in quantity and in quality of the works, most of them being published in respectable international journals on the subject. The (...) chapters of this volume are forwarded by a general introduction, which aims to sketch not only the contents of the chapters, but it is conceived as a historical and conceptual guide to the development of the field in Brazil. The introduction intends to be useful to the reader, and not only to the specialist, helping them to evaluate the increase in production of this country within the international context. (shrink)

This paper explores Charles Darwin’s hypothesis of pangenesis through a popular and professional reception history. First published in The Variation of Animals and Plants under Domestication (1868), pangenesis stated that inheritance can be explained by sub-cellular “gemmules” which aggregated in the sexual organs during intercourse. Pangenesis thereby accounted for the seemingly arbitrary absence and presence of traits in offspring while also clarifying some botanical and invertebrates’ limb regeneration abilities. I argue that critics largely interpreted Variation as an extension of On (...) the Origin of Species by Means of Natural Selection (1859), while pangenesis was an extension of natural selection. Contrary to claims that pangenesis was divorced from natural selection by its reliance on the inheritance of acquired characters, pangenesis’s mid nineteenth-century reception suggests that Darwin’s hypothesis responded directly to selection’s critics. Using Variation’s several editions, periodical reviews, and personal correspondence I assess pangenesis popularly, professionally, and biographically to better understand Variation’s impact on 1860s and 70s British evolutionism and inheritance. -/- . (shrink)

Raphael Meldola (1849-1915), an industrial chemist and keen naturalist, under the influence of Darwin, brought new German studies on evolution by natural selection that appeared in the 1870s to the attention of the British scientific community. Meldola's special interest was in mimicry among butterflies; through this he became a prominent neo-Darwinian. His wide-ranging achievements in science led to appointments as president of important professional scientific societies, and of a local club of like-minded amateurs, particularly field naturalists. This is an account (...) of Meldola's early scientific connections and studies related to entomology and natural selection, his contributions to the study of mimicry, and his promotion in the mid-1890s of a more theory driven approach among entomologists. (shrink)

In this essay I discuss the contents and the context of Italian zoologist and entomologist Carlo Emery’s discussion of the germ-plasm theory. August Weismann considered him one of his very few creditable supporters, and encouraged him to publish his theoretical reflections. In his Gedanken zur Descendenz- und Vererbungstheorie, which appeared between 1893 and 1903 as a series of five essays in the journal Biologisches Zentralblatt, Emery developed a very personal account, applying the concept of determinants to problems like atavism, sexual (...) dimorphism, speciation, geographical isolation, transmission of characters, and putting forward, as early as 1903, the idea of a genetic program. (shrink)

The concepts of hierarchical organization, genetic determinism and biological specificity have played a crucial role in biology as a modern experimental science since its beginnings in the nineteenth century. The idea of genetic information and genetic determination was at the basis of molecular biology that developed in the 1940s with macromolecules, viruses and prokaryotes as major objects of research often labelled “reductionist”. However, the concepts have been marginalized or rejected in some of the research that in the late 1960s began (...) to focus additionally on the molecularization of complex biological structures and functions using systems approaches. This paper challenges the view that ‘molecular reductionism’ has been successfully replaced by holism and a focus on the collective behaviour of cellular entities. It argues instead that there are more fertile replacements for molecular ‘reductionism’, in which genomics, embryology, biochemistry, and computer science intertwine and result in research that is as exact and causally predictive as earlier molecular biology. (shrink)

A number of areas of biology raise questions about what is of value in the natural environment and how we ought to behave towards it: conservation biology, environmental science, and ecology, to name a few. Based on my experience teaching students from these and similar majors, I argue that the field of environmental ethics has much to teach these students. They come to me with pent-up questions and a feeling that more is needed to fully engage in their subjects, and (...) I believe some exposure to environmental ethics can help focus their interests and goals. I identify three primary areas in which environmental ethics can con- tribute to their education. The first is an examination of who (or what) should be considered to be part of our moral community (i.e., the community to whom we owe direct duties). Is it humans only? Or does it include all sentient life? Or all life? Or ecosystems considered holistically? Often, readings implicitly assume one or more of these answers; the goal is to make the student more sensitive to these implicit claims and to get them to think about the different reasons that support them. The second area, related to the first, is the application of the different answers concerning the extent of the ethical community to real environmental issues and problems. Students need to be aware of how the different answers concerning the moral community can imply conflicting answers for how we should act in certain cases and to think about ways to move toward conflict resolution. The third area in which environmental ethics can contribute is a more conceptual one, focusing on central concepts such as biodiversity, sustainability, species, and ecosystems. Exploring and evaluating various meanings of these terms will make students more reflective and thoughtful citizens and biologists, sensitive to the implications that different conceptual choices make. (shrink)

En lo que sigue, se reconstruye el dominio de teorías relativas a la herencia biológica, propuestas durante el periodo 1865-1902. Se trata de un episodio científico de mucha controversia y audaces especulaciones, libres de los constreñimientos de un paradigma establecido. En consecuencia, surgieron propuestas muy diversas, para las cuales no empata bien la categoría metateórica de red. De cualquier manera, los elementos teóricos detectados sí guardan vínculos entre sí, debido a que comparten ciertas estructuras, y esto permite introducir mediante un (...) arreglo reticular la idea de dominio, donde la naturaleza de los vínculos no alude a especializaciones de leyes fundamentales sino a la secuencia en el armado de subestructuras. El trabajo explora esta posibilidad combinando el aparato del programa estructuralista con la técnica ordenadora denominada Análisis Formal de Conceptos : en concreto se aplica dicho procedimiento a una muestra de veinte reconstrucciones, de elementos teóricos relativos a la herencia entre 1865 y 1902. (shrink)

Stem cells did not become a proper research object until the 1960 s. Yet the term and the basic mind-set—namely the conception of single undifferentiated cells, be they embryonic or adult, as the basic units responsible for a directed process of development, differentiation and increasing specialisation—were already in place at the end of the nineteenth century and then transmitted on a non-linear path in the form of tropes and diagrams. Ernst Haeckel and August Weismann played a special role in this (...) story. The first coined the term Stammzelle (stem cell), the second was the author of the first cellular stem-tree diagram. Even today, I shall argue, the understanding of stem cells, especially the popular perception, is to a large extent a Haeckelian–Weismannian one. After having demonstrated this, by analysing the terminology, in this essay I will focus on the use of cytogenetic tree diagrams between 1892 and 1925 and on the tacit understanding of stem cells that they transmit. (shrink)

RESUMENEl desarrollo embriológico es un fenómeno que ha inspirado la especulación filosófica desde temprano en la historia del pensamiento. Desde los tiempos de Aristóteles dos modelos conceptuales antitéticos se han utilizado tradicionalmente para comprender la embriogénesis: o el embrión posee ya una forma o estructura, o ésta se forma de nuevo en cada generación. Nuestro objetivo en este artículo es mostrar que el contraste entre la posición preformacionista y epigenética persiste a pesar de los formidables avances teóricos y experimentales de (...) la biología del desarrollo contemporánea. El preformacionismo y la epigénesis han perfeccionado constantemente sus posiciones en el curso de la historia con el fin de responder a los retos conceptuales de la época. Este continuo proceso de transformación ha dado lugar a una convergencia parcial entre las dos posiciones. Sin embargo, vamos a argumentar que, a pesar de los esfuerzos por conciliar ambas posturas, esta antinomia, que se erige como una de las más fundamentales de la biología, no será fácil de superar. ABSTRACTThe process of development of the embryo has inspired philosophical speculation since the advent of Western thought. Since the time of Aristotle two antithetical conceptual models have traditionally been used to understand embryogenesis: either form or structure is preformed in the embryo or it is newly formed with each generation. Our aim in this article is to show that the contrast between the pre-formationist and epigenetic positions persists despite the formidable theoretical and experimental advances of contemporary developmental biology. Pre-formationism and epigenesis have constantly refined their positions in the course of history in order to answer the conceptual challenges of each epoch. This process of continuous transformation has resulted in a partial convergence of the two positions. However, we shall argue that, despite the partial successes of this process of continuous convergence, one of the most fundamental antinomies in biology persists. (shrink)

Early in his career Thomas Hunt Morgan was interested in embryology and dedicated his research to studying organisms that could regenerate. Widely regarded as a regeneration expert, Morgan was invited to deliver a series of lectures on the topic that he developed into a book, Regeneration. In addition to presenting experimental work that he had conducted and supervised, Morgan also synthesized and critiqued a great deal of work by his peers and predecessors. This essay probes into the history of regeneration (...) studies by looking in depth at Regeneration and evaluating Morgan’s contribution. Although famous for his work with fruit fly genetics, studying Regeneration illuminates Morgan’s earlier scientific approach which emphasized the importance of studying a diversity of organisms. Surveying a broad range of regenerative phenomena allowed Morgan to institute a standard scientific terminology that continues to inform regeneration studies today. Most importantly, Morgan argued that regeneration was a fundamental aspect of the growth process and therefore should be accounted for within developmental theory. Establishing important similarities between regeneration and development allowed Morgan to make the case that regeneration could act as a model of development. The nature of the relationship between embryogenesis and regeneration remains an active area of research. (shrink)

Stem-cell nomenclature is in a muddle! So-called stem cells may be self-renewing or emergent, oligopotent (uni- and multipotent) or pluri- and totipotent, cells with perpetual embryonic features or cells that have changed irreversibly. Ambiguity probably seeped into stem cells from common usage, flukes in biology's history beginning with Weismann's divide between germ and soma and Haeckel's biogenic law and ending with contemporary issues over the therapeutic efficacy of adult versus embryonic cells. Confusion centers on tissue dynamics, whether stem cells are (...) properly members of emerging or steady-state populations. Clarity might yet be achieved by codifying differences between cells in emergent populations, including embryonic stem and embryonic germ (ES and EG) cells in tissue culture as opposed to self-renewing (SR) cells in steady-state populations. BioEssays 28: 301–308, 2006. © 2006 Wiley Periodicals, Inc. (shrink)

Heritable traits are predominantly encoded within genomic DNA, but it is now appreciated that epigenetic information is also inherited through DNA methylation, histone modifications, and small RNAs. Several examples of transgenerational epigenetic inheritance of traits have been documented in plants and animals. These include even the inheritance of traits acquired through the soma during the life of an organism, implicating the transfer of epigenetic information via the germline to the next generation. Small RNAs appear to play a significant role in (...) carrying epigenetic information across generations. This review focuses on how epigenetic information in the form of small RNAs is transmitted from the germline to the embryos through the gametes. We also consider how inherited epigenetic information is maintained across generations in a small RNA‐dependent and independent manner. Finally, we discuss how epigenetic traits acquired from the soma can be inherited through small RNAs. (shrink)