Contemporary biological research has suggested that some host–microbiome multispecies systems (referred to as “holobionts”) can in certain circumstances evolve as unique biological individual, thus being a unit of selection in evolution. If this is so, then it is arguably the case that some biological adaptations have evolved at the level of the multispecies system, what we call hologenomic adaptations. However, no research has yet been devoted to investigating their nature, or how these adaptations can be distinguished from adaptations at the (...) species-level (genomic adaptations). In this paper, we cover this gap by investigating the nature of hologenomic adaptations. By drawing on the case of the evolution of sanguivory diet in vampire bats, we argue that a trait constitutes a hologenomic adaptation when its evolution can only be explained if the holobiont is considered the biological individual that manifests this adaptation, while the bacterial taxa that bear the trait are only opportunistic beneficiaries of it. We then use the philosophical notions of emergence and inter-identity to explain the nature of this form of individuality and argue why it is special of holobionts. Overall, our paper illustrates how the use of philosophical concepts can illuminate scientific discussions, in the trend of what has recently been called metaphysics of biology. (shrink)

Microbiome research shows that human health is foundationally intertwined with the ecology of microbial communities living on and in our bodies. This challenges the categorical separation of organisms from environments that has been central to biomedicine, and questions the boundaries between them. Biomedicine is left with an empirical problem: how to understand causal pathways between host health, microbiota and environment? We propose a conceptual tool – environmentality – to think through this problem. Environmentality is the state or quality of being (...) an environment for something else in a particular context: a fully perspectival proposition. Its power lies partly in what Isabelle Stengers has called the efficacy of the word itself, contrasting the dominant sense of the word environment as something both external and fixed. Through three case studies, we argue that environmentality can help think about the causality of microbiota vis-a-vis host health in a processual, relational and situated manner, across scales and temporalities. We situate this intervention within historical trajectories of thought in biomedicine, focusing on the challenge microbiome research poses to an aperspectival body. We argue that addressing entanglements between microbial and human lives requires that the environment is brought into the clinic, thus shortening the conceptual gap between medicine and public health. (shrink)

An understanding of the factors behind the evolution of multicellularity is one of today’s frontiers in evolutionary biology. This is because multicellular organisms are made of one subset of cells with the capacity to transmit genes to the next generation and another subset responsible for maintaining the functionality of the organism, but incapable of transmitting genes to the next generation. The question arises: why do somatic cells sacrifice their lives for the sake of germline cells? How is germ/soma separation maintained? (...) One conventional answer refers to inclusive fitness theory, according to which somatic cells sacrifice themselves altruistically, because in so doing they enhance the transmission of their genes by virtue of their genetic relatedness to germline cells. In the present article we will argue that this explanation ignores the key role of policing mechanisms in maintaining the germ/soma divide. Based on the pervasiveness of the latter, we argue that the role of altruistic mechanisms in the evolution of multicellularity is limited and that our understanding of this evolution must be enriched through the consideration of coercion mechanisms. (shrink)

According to the mainstream position in the bioethical definition of death debate, death is to be equated with the cessation of an organism. Given such a perspective, some bioethicists uphold the position that brain-dead patients are dead, while others claim that they are alive. Regardless of the specific opinion on the status of brain-dead patients, the mere bioethical concept of death, according to many bioethicists, has the merit of being unanimous and univocal, as well as grounded in biology. In the (...) present article, we challenge such a thesis. We provide evidence that theoretical biology operates with a plurality of equally valid organismic concepts, which imply different conclusions regarding the organismal status of a brain-dead patient. Moreover, the theoretical biology concepts of an organism are very distant from the view on an organism that appears by way of bioethicists theorizing on death. We conclude that if death is to be understood as the cessation of an organism, there is no single correct answer to the question of whether a brain-dead patient is alive or dead. (shrink)

Much of the debate over the definition and criteria for determining our death has focused on disagreement over the correct biological account of death, i.e., what it means for any organism to die. In this paper, we argue that this exclusive focus on the biology of death is misguided, because it ignores ethical and social factors that bear on the acceptability of criteria for determining our death. We propose that attention shift from strictly biological considerations to ethical and social considerations (...) that bear on the determination of what we call “civil death.” We argue for acceptance of a neurological criterion for determining death on grounds that it is the most reasonable way to synthesize biological, ethical, and social considerations about our death.. (shrink)

Immunology and its philosophy are a primary source for thinking about biological individuality. Through its discriminatory function, the immune system is believed to delineate organism and environment within one generation, thus defining the physiological individual. Based on the paradigmatic instantiations of immune systems, immune interactions and, thus, the physiological individual are believed to last only for one generation. However, in recent years, transgenerationally persisting immune responses have been reported in several phyla, but the consequences for physiological individuality have not yet (...) been explored. In this article, I will introduce an invertebrate immune system that is RNA-based and operates through a heritable silencing/licensing paradigm. I will discuss how such a perspective on immune systems can illuminate our conceptions of individuality. I will particularly introduce an account of immunological individuality that is not restricted to one generation. (shrink)

The hologenome concept of evolution is a hypothesis about the evolution of animals and plants. It asserts that the evolution of animals and plants was partially triggered by their interactions with their symbiotic microbiomes. In that vein, the hologenome concept posits that the holobiont (animal host + symbionts of the microbiome) is a unit of selection. -/- The hologenome concept has been severely criticized on the basis that selection on holobionts would only be possible if there were a tight transgenerational (...) host-genotype-to-symbiont-genotype connection. As our current evidence suggests that this is not the case for most of the symbiont species that compose the microbiome of animals and plants, the opportunity for holobiont selection is very low in relation to the opportunity for selection on each of the species that compose the host microbiome. Therefore, holobiont selection will always be disrupted ‘from below’, by selection on each of the species that compose the microbiome. -/- This thesis constitutes a conceptual effort to defend philosophically the hologenome concept. I argue that the criticism according to which holobiont selection requires tight transgenerational host-genotype-to-symbiont-genotype connection is grounded on a metaphysical view of the world according to which the biological hierarchy needs to be nested, such that each new level of selection includes every entity from below. Applied to hologenomes, it entails that the hologenome is a collection of genomes, and selection of hologenomes is assumed to entail cospeciation of the host with the species that constitute its microbiome. -/- Against that interpretation, I propose the ‘stability of traits’ account, according to which hologenome evolution is the result of the action of natural selection in a non-nested hierarchical world. In that vein, hologenome evolution does not entail cospeciation, and thus it does not require tight transgenerational host-genotype-to-symbiont-genotype connection. By embracing a multilevel selection perspective, I argue that hologenome evolution results from the simultaneous action of natural selection on each of the lineages that compose the microbiome, and on the assemblage composed by the host genome plus the functional traits of its microbiome. Hologenome selection occurs when the evolution of the traits of the microbiome result from their effects on the fitness of the host, and it can take the form of multilevel selection 1, or multilevel selection 2. In both cases, hologenome selection entails the evolution of microbiome traits, as well as evolution of the host genome, rather than cospeciation of lineages. (shrink)

The Central Dogma of molecular biology, which holds that DNA makes protein and not the other way around, is as influential as it is controversial. Some believe the Dogma has outlived its usefulness, either because it fails to fully capture the ins-and-outs of protein synthesis (Griffiths and Stotz, 2013; Stotz, 2006), because it turns on a confused notion of information (Sarkar, 2004), or because it problematically assumes the unidirectional flow of information from DNA to protein (Gottlieb, 2001). This paper evaluates (...) an underexplored defense of the Dogma, which relies on the assumption that the Dogma and the Inheritance of Acquired Traits, a principle which dates as far back as Jean Baptiste-Lamarck, are incompatible principles (Smith, 1993; Judson, 1979; Dawkins, 1970; Cobb, 2017; Wilkins, 2002; Graur, 2018). By appealing to empirical evidence in molecular science, I argue that this apparent incompatibility is indeed merely apparent. I conclude by briefly demonstrating how these considerations bear on the topic of conceptual pluralism in the philosophy of science (Stencel and Proszewska, 2018; Lu and Bourrat, 2018). (shrink)

While agreeing with the main conclusion of Dominic Wilkinson and colleagues (Wilkinson, Butcherine, and Savulescu 2019), namely, that there is no moral difference between treatment withholding and withdrawal as such, we wish to criticize their approach on the basis that it treats the widespread acceptance of withdrawal aversion (WA) as a cognitive bias. Wilkinson and colleagues understand WA as “a nonrational preference for withholding (WH) treatment over withdrawal (WD) of treatment” (22). They treat WA as a manifestation of loss aversion (...) and refer to Kahneman and colleagues (1991), which defined this effect as follows: “the disutility of giving up an object is greater that the utility associated with acquiring it” (194). In a previous work, Wilkinson and Savulescu understood nonequivalence between treatment withholding and withdrawal as a reflection of slightly different, although related, phenomena: status quo bias or omission bias (Wilkinson and Savulescu 2012, 130–131). In neither of these two papers do they describe precisely the relation between these well-known psychological effects and WA, nor do they explain why they treat these effects as examples of nonrational preferences, despite the fact that these issues have been the subject of wide-ranging discussions on the intersection of psychology, economy, and philosophy. (shrink)

The organism is the central entity in biological science. However, consensus with regard to the definition of the underlying concept is lacking. Moreover, several ambiguous life forms exist that challenge current definitions of the term. Based on a comprehensive analysis of the available literature, we provide an overview of the criteria and approaches that have been previously used to define organismality. In addition, we highlight non-paradigmatic biological entities to identify problems that challenge definitions of organismal units. To address these issues, (...) we propose a cross-disciplinary definition of the organism concept and provide a list of key criteria that allow both paradigmatic and non-paradigmatic cases to be unequivocally classified. In this way, our work not only provides newcomers with an overview of this exciting field, but also enhances communication across disciplines. (shrink)

The concept of superorganism has a mixed reputation in biology—for some it is a convenient way of discussing supra-organismal levels of organization, and for others, little more than a poetic metaphor. Here, I show that a considerable step forward in the understanding of superorganisms results from a thorough review of the supra-organismal levels of organization now known to exist among the “unicellular” protists. Limiting the discussion to protists has enormous advantages: their bodies are very well studied and relatively simple, and (...) they exhibit an enormous diversity of anatomies and lifestyles. This allows for unprecedented resolution in describing forms of supra-organismal organization. Here, four criteria are used to differentiate loose, incidental associations of hosts with their microbiota from “actual” superorganisms: obligatory character, specific spatial localization of microbiota, presence of attachment structures and signs of co-evolution in phylogenetic analyses. Three groups—that have never before been described in the philosophical literature—merit special attention: Symbiontida, Oxymonadida and Parabasalia. Specifically, it is argued that in certain cases—for Bihospites bacati and Calkinsia aureus, Streblomastix strix, Joenia annectens and Mixotricha paradoxa and Kentrophoros —it is fully appropriate to describe the whole protist-microbiota assocation as a single organism and its elements as “tissues” or, arguably, even “organs”. To account for this level of biological complexity, I propose the term “structured superorganism”. (shrink)

The units or levels of selection debate concerns the question of what kind of biological systems are stable enough that part of their evolution is a result of the process of natural selection acting at their level. Traditionally, the debate has concerned at least two different, though related, questions: the question of the level at which interaction with the environment occurs, and the question of the level at which reproduction occurs. In recent years, biologists and philosophers have discussed a new (...) aspect of this debate, namely the possibility that certain multi-species consortia formed by a host and its microbiome may act as a unit of selection. This thesis, however, has not been without criticism, as it is doubtful that such consortia could meet the conditions required to achieve the degree of stability that would allow them to experience natural selection. The purpose of this paper is to systematically examine such criticisms and to defend the thesis that the holobiont/hologenome can act as a genuine level of selection both in the form of an interactor and in the form of a reproducer. To do so, it will be argued that the microbiome should be characterized in functional rather than taxonomic terms. (shrink)

This paper addresses the topic of determinism in contemporary microbiome research. I distinguish two types of deterministic claims about the microbiome, and I show evidence that both types of claims are present in the contemporary literature. First, the idea that the host genetics determines the composition of the microbiome which I call “host-microbiome determinism”. Second, the idea that the genetics of the holobiont (the individual unit composed by a host plus its microbiome) determines the expression of certain phenotypic traits, which (...) I call “microbiome-phenotype determinism”. Drawing on the stability of traits conception of individuality (Suárez in Hist Philos Life Sci 42:11, 2020) I argue that none of these deterministic hypotheses is grounded on our current knowledge of how the holobiont is transgenerationally assembled, nor how it expresses its phenotypic traits. (shrink)

Callender [2017] claims that contemporary science demonstrates that there is no objective present and no objective flow of time, especially since all sensed events come from the past, our various senses need different amounts of time to react, and there are enough asymmetries in the physical world to explain our experience of time. This paper holds that, although Callender’s arguments for the subjectivity of the flow of time are unconvincing, the scientific discoveries and arguments he indicates can still be applied (...) to improve theories of the objective flow of time. The paper develops precisely such a theory, one which introduces multiple individual proper presents for all of the objects that make up our world. (shrink)