Eukaryotic origins are heavily debated. The author as well as others have proposed that they are inextricably linked with the arrival of a pre‐mitochondrion of alphaproteobacterial‐like ancestry, in a so‐called symbiogenic scenario. The ensuing mutual adaptation of archaeal host and endosymbiont seems to have been a defining influence during the processes leading to the last eukaryotic common ancestor. An unresolved question in this scenario deals with the means by which the bacterium ends up inside. Older hypotheses revolve around the application (...) of known antagonistic interactions, the bacterium being prey or parasite. Here, in reviewing the field, the author argues that such models share flaws, hence making them less likely, and that a “pre‐symbiotic stage” would have eased ongoing metabolic integration. Based on this the author will speculate about the nature of the (endo) symbiosis that started eukaryotic evolution–in the context of bacterial entry being a relatively “early” event–and stress the differences between this uptake and subsequent ones. He will also briefly discuss how the mutual adaptation following the merger progressed and how many eukaryotic hallmarks can be understood in light of coadaptation. Also see the video abstract here https://youtu.be/ekqtNleVJpU. (shrink)

While philosophers of science have marginally discussed concepts such as ‘nutrient’, ‘naturalness’, ‘food’, or the ‘molecularization’ of nutrition, they have yet to seriously engage with the nutrition sciences. In this paper, I offer one way to begin this engagement by investigating conceptual challenges facing the burgeoning field of nutritional ecology and the question of how organisms construct a ‘balanced’ diet. To provide clarity, I propose the distinction between nutrient balance as a property of foods or dietary patterns and nutrient balancing (...) as an evolved capacity to regulate nutrient intake. This distinction raises conceptual and empirical issues, such as what properties constitute this capacity and whether they are the same in all organisms. Additionally, while scientists use the term ‘balancing’, its intension and extension need further clarification. Based on the literature, the properties of external nutrient detection, internal sensing of nutrient levels, and organismal regulation could provide a basic recipe for nutrient balancing. Next, using an evolutionary lens, I examine nutrient acquisition in some prokaryotes, slime molds, simple multicellular eukaryotes, and in the quirks of multicellular metabolism to raise questions about the origins and universality of balancing. Finally, I build on this explication of balance and balancing by considering how obesity and cancer might respectively elucidate problems of organismal nutrient imbalances versus disrupted cellular nutrient balancing. (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)

In order to introduce protists to philosophers, we outline the diversity, classification, and evolutionary importance of these eukaryotic microorganisms. We argue that an evolutionary understanding of protists is crucial for understanding eukaryotes in general. More specifically, evolutionary protistology shows how the emphasis on understanding evolutionary phenomena through a phylogeny-based comparative approach constrains and underpins any more abstract account of why certain organismal features evolved in the early history of eukaryotes. We focus on three crucial episodes of this history: the origins (...) of multicellularity, the origin of sex, and the origin of the eukaryote cell. Despite ongoing uncertainty about where the root of the eukaryote tree lies, and residual questions about the precise endosymbioses that have produced a diversity of photosynthesizing eukaryotes, evolutionary protistology has illuminated with considerable clarity many aspects of protist evolution. Our main message in light of evolutionary protistology is that these ‘other eukaryotes’ are in fact the organisms through which the rest of the eukaryotes should be understood. (shrink)

Much is being written these days about integration, its desirability and even its necessity when complex research problems are to be addressed. Seldom, however, do we hear much about the failure of such efforts. Because integration is an ongoing activity rather than a final achievement, and because today’s literature about integration consists mostly of manifesto statements rather than precise descriptions, an examination of unsuccessful integration could be illuminating to understand better how it works. This paper will examine the case of (...) prokaryote phylogeny and its apparent failure to achieve integration within broader tree-of-life accounts of evolutionary history. Despite the fact that integrated databases exist of molecules pertinent to the phylogenetic reconstruction of all lineages of life, and even though the same methods can be used to construct phylogenies wherever the organisms fall on the tree of life, prokaryote phylogeny remains at best only partly integrated within tree-of-life efforts. I will examine why integration does not occur, compare it with integrative practices in animal and other eukaryote phylogeny, and reflect on whether there might be different expectations of what integration should achieve. Finally, I will draw some general conclusions about integration and its function as a ‘meta-heuristic’ in the normative commitments guiding scientific practice. (shrink)

Protistology, and evolutionary protistology in particular, is experiencing a golden research era. It is an extended one that can be dated back to the 1970s, which is when the molecular rebirth of microbial phylogeny began in earnest. John Archibald, a professor of evolutionary microbiology at Dalhousie University, focuses on the beautiful story of endosymbiosis in his book, John Archibald, One Plus One Equals One: Symbiosis and the Origin of Complex Life. However, this historical narrative could be treated as synecdochal of (...) how the molecular revolution has changed evolutionary biology forever, and that is how Archibald has structured his book. I will address the encompassing theme of molecular methods in detail, but also pay careful attention to the endosymbiosis thread in its own right. (shrink)

The model of major transitions in evolution devised by Maynard Smith and Szathmáry has exerted tremendous influence over evolutionary theorists. Although MTE has been criticized for inconsistently combining different types of event, its ongoing appeal lies in depicting hierarchical increases in complexity by means of evolutionary transitions in individuality. In this paper, we consider the implications of major evolutionary events overlooked by MTE and its ETI-oriented successors, specifically the biological oxygenation of Earth, and the acquisitions of mitochondria and plastids. By (...) reflecting on these missed events, we reveal a central philosophical disagreement over the explanatory goals of major transitions theory that has yet to be made explicit in the literature. We go on to argue that this philosophical disagreement is only reinforced by Szathmáry’s recent revisions of MTE in the form of MTE 2.0. This finding motivates us to propose an alternative explanatory strategy: specifically, an interactionist metabolic perspective on major transitions. A metabolic framework not only avoids many of the criticisms that beset classic and revised MTE models, but also accommodates missing events and provides crucial explanatory components for standard major transitions. Although we do not provide a full-blown alternative theory and do not claim to achieve unity, we explain why foregrounding metabolism is crucial for any attempt to capture the major turning points in evolution, and why it does not lead to unmanageable pluralism. (shrink)

Biological atomism postulates that all life is composed of elementary and indivisible vital units. The activity of a living organism is thus conceived as the result of the activities and interactions of its elementary constituents, each of which individually already exhibits all the attributes proper to life. This paper surveys some of the key episodes in the history of biological atomism, and situates cell theory within this tradition. The atomistic foundations of cell theory are subsequently dissected and discussed, together with (...) the theory’s conceptual development and eventual consolidation. This paper then examines the major criticisms that have been waged against cell theory, and argues that these too can be interpreted through the prism of biological atomism as attempts to relocate the true biological atom away from the cell to a level of organization above or below it. Overall, biological atomism provides a useful perspective through which to examine the history and philosophy of cell theory, and it also opens up a new way of thinking about the epistemic decomposition of living organisms that significantly departs from the physicochemical reductionism of mechanistic biology. (shrink)

The initial relationships between organisms leading to endosymbiosis and the first eukaryote are currently a topic of hot debate. Here, I present a theory that offers a gradual scenario in which the origins of phagocytosis and mitochondria are intertwined in such a way that the evolution of one would not be possible without the other. In this scenario, the premitochondrial bacterial symbiont became initially associated with a protophagocytic host on the basis of cooperation to kill prey with symbiont‐produced toxins and (...) reactive oxygen species (ROS). Subsequently, the cooperation was focused on the digestion stage, through the acidification of the protophagocytic cavities via exportation of protons produced by the aerobic respiration of the symbiont. The host gained an improved phagocytic capacity and the symbiont received organic compounds from prey. As the host gradually lost its membrane energetics to develop lysosomal digestion, respiration was centralized in the premitochondrial symbiont for energy production for the consortium. (shrink)

Environmental heterogeneity is invoked as a key explanatory factor in the adaptive evolution of a surprisingly wide range of phenomena. This article aims to analyze this explanatory scheme of categorizing traits or properties as adaptations to environmental heterogeneity. First it is suggested that this scheme can be understood as a reaction to how heterogeneity adaptations were discounted or ignored in the modern synthesis. Then a positive account is proposed, distinguishing between two broad categories of adaptation to environmental heterogeneity: properties selected (...) for by well-defined patterns of environmental heterogeneity, and properties that help organisms exploit novel patterns of environmental heterogeneity. (shrink)

Philosophers have usually highlighted how the weakness and paucity of historical evidence underdetermine the choice between rival historical explanations. Focusing underdetermination on the link between theory and evidence comes, I argue, with three assumptions: competing hypotheses are easy to generate, investigators agree on the constitution and interpretation of the evidence and a plurality of hypotheses is a useful evil to reach consensus. The last assumption implies that the sustained coexistence of incompatible hypotheses is considered as a scientific failure. I argue (...) that this negative vision of sustained disagreement has monistic undertones. By drawing from a case study in evolutionary biology, this paper defends a form of scientific pluralism. Firstly, I show that underdetermination is not only found at the inferential level but also at the level of the constitution and interpretation of the evidence, on the choice of investigative scaffolds and when interpreting background theories. Because of that, competing hypotheses exhibit a degree of methodological incommensurability. While catastrophic from a monistic standpoint, I defend that scientific pluralism gives a different, and I think richer, account of such situations. On the plus side, competing approaches benefit from their sustained coexistence and interaction. I argue that this generates direct and indirect epistemic goods independently of whether the controversy is solved. Scientific pluralism also shifts our attention from achieving consensus to managing disagreement. The challenge becomes to maintain the conditions for fruitful interactions in a community with incommensurable approaches and heterogeneous expertise. (shrink)

This article is a study of the role and use of evidence in the evaluation of claims in the historical sciences. In order to do this, I develop a “snapshot” approach to Toulmin schemas. This framework is applied to the case of Archezoa, an initially supported then eventually rejected hypothesis in evolutionary biology. From this case study, I criticize Cleland’s “smoking gun” account of the methodology of the historical sciences. I argue that Toulmin schemas are conceptually precise tools that allow (...) for the building of enriched reconstructions of evidential reasoning. From the application of this framework, I discuss three ways in which the construction and use of facts in the historical sciences are theory-laden. Despite its inherent limits, TS are heuristically useful tools to identify epistemic moves that could be further investigated. It also sheds light on the positive roles of speculation in the historical sciences. Finally, I argue that it provides a context-specific and individuated understanding of hypothesis evaluation in the historical sciences. Overall, I think the application of Toulmin schemas to cases of evidential reasoning in the historical sciences is a promising descriptive and heuristic tool for philosophers of science. (shrink)