Both concepts of the holobiont and the immune system are at the heart of an ongoing scientific and philosophical examination concerning questions of the organism’s individuality and identity as well as the relations between organisms and their environment. Examining the holobiont, the question of boundaries and individuality is challenging because it is both an assemblage of organisms with physiological cohesive aspects. I discuss the concept of immunity and the immune system function from the holobiont perspective. Because of the host-microbial close (...) relations of codependence and interdependence, the holobiont is more often than not confused with the host, as the host is the domain in which this entity exists. I discuss the holobiont unique ecological characteristics of microbial assemblages connected to a host in a network of interactions in which the host is one of the organisms in the community but also its landscape. Therefore, I suggest viewing the holobiont as a host-ecosystem and discuss the implication of such a view on the concept of immunity and the meaning of protection. Furthermore, I show that viewing the holobiont as a host ecosystem opens the possibility of using the same ecological definition of boundaries and immunity dealing with an ecological system. Thus, the holobiont’s boundaries and immunity are defined by the persistence of its complex system of interactions integrating existing and new interactions. This way of thinking presents a notion of immunity that materializes as the result of the complex interdependence relations between the different organisms composing the holobiont similar to that of an ecosystem. Taking this view further, I discuss the notion of immunogenicity that is ontologically heterogeneous with various causal explanations of the processes of tolerance and targeted immune response. Finally, I discuss the possible conceptualization of already existing and new biomedical practices. (shrink)

Biological individuality is a notoriously thorny topic for biologists and philosophers of biology. In this paper we argue that biological individuality presents multiple, interconnected questions for biologists and philosophers that together form a problem agenda. Using a case study of an interdisciplinary research group in ecology, behavioral and evolutionary biology, we claim that a debate on biological individuality that seeks to account for diverse practices in the biological sciences should be broadened to include and give prominence to questions about uniqueness (...) and temporality. We show that broadening the problem agenda of biological individuality draws attention to underrecognized philosophical issues and discussions and thereby organizes and enriches the existing debate. (shrink)

Recent attention to complex group-level behavior amongst bacteria has led some to conceive of multicellular clusters of bacteria as individuals. In this article, I assess these recent claims by first drawing a distinction between two concepts of individuality: physiological and evolutionary. I then survey cases that are representative of three different modes of growth: myxobacteria (surface-attached agglomerative growth), Bacillus subtilis (agglomerative growth not attached to a surface), and cyanobacteria (filamentous growth). A closer look at these cases indicates that multicellular individuality (...) among bacteria is remarkably complex. Physiologically, the three cases of multicellular clusters do not form physiological individuals. But matters are different when it comes to evolutionary individuality; although multicellular clusters that grow by agglomeration are not highly individuated, filament-forming groups achieve a relatively high degree of individuality. I also suggest that debates about bacterial multicellular individuality may have been obscured by a failure to see that selection on highly individuated groups is by no means the only mechanism to bring about the complex group-level behaviors that have led some to view bacteria as multicellular individuals. (shrink)

We assess the arguments for recognising functionally integrated multispecies consortia as genuine biological individuals, including cases of so-called ‘holobionts’. We provide two examples in which the same core biochemical processes that sustain life are distributed across a consortium of individuals of different species. Although the same chemistry features in both examples, proponents of the holobiont as unit of evolution would recognize one of the two cases as a multispecies individual whilst they would consider the other as a compelling case of (...) ecological dependence between separate individuals. Some widely used arguments in support of the ‘holobiont’ concept apply equally to both cases, suggesting that those arguments have misidentified what is at stake when seeking to identify a new level of biological individuality. One important aspect of biological individuality is evolutionary individuality. In line with other work on the evolution of individuality, we show that our cases can be distinguished by focusing on the fitness alignment between the partners of the consortia. We conclude that much of the evidence currently presented for the ubiquity and importance of multi-species individuals is simply not to the point, at least unless the issue of biological individuality is firmly divorced from the question of evolutionary individuality. (shrink)

Individuality is an important concept in biology, yet there are many non-equivalent criteria of individuality expressed in different kinds of biological individuals. This article evaluates these different kinds in terms of their capacity to support explanatory generalizations over the systems they individuate. Viewing the problem of individuality from this perspective promotes a splitting strategy in which different kinds make different epistemic trade-offs that suit them for different explanatory roles. I argue that evolutionary individuals, interpreted as forming a functional kind, face (...) difficulties of individuation and explanatory power that are mitigated by relying on more structurally based properties and non-evolutionary kinds. 1Introduction2Kinds of Biological Individuals3Evolutionary Individuals and Functional Kinds4Evolutionary versus Non-evolutionary Kinds of Individuals 4.1Physiological individuality4.2Ecological individuality4.3Developmental individuality5Conclusion. (shrink)

Mechanisms are said to consist of two kinds of components, entities and activities. In the first half of this chapter, I examine what entities and activities are, how they relate to well-known ontological categories, such as processes or dispositions, and how entities and activities relate to each other (e.g., can one be reduced to the other or are they mutually dependent?). The second part of this chapter analyzes different criteria for individuating the components of mechanisms and discusses how real the (...) boundaries of mechanisms are. (shrink)

The definition of biological individuality is one of the most discussed topics in philosophy of biology, but current debate has focused almost exclusively on evolution-based accounts. Moreover, several participants in this debate consider the notions of a biological individual and an organism as equivalent. In this paper, I show that the debates would be considerably enriched and clarified if philosophers took into account two elements. First, physiological fields are crucial for the understanding of biological individuality. Second, the category of biological (...) individuals should be divided into two subcategories: physiological individuals and evolutionary individuals, which suggests that the notions of organism and biological individual should not be used interchangeably. I suggest that the combination of an evolutionary and a physiological perspective will enable biologists and philosophers to supply an account of biological individuality that will be both more comprehensive and more in accordance with scientific practices. (shrink)

Biological individuality is a major topic of discussion in biology and philosophy of biology. Recently, several objections have been raised against traditional accounts of biological individuality, including the objections of monism, theory-centrism, ahistoricity, disciplinary isolationism, and the multiplication of conceptual uncertainties. In this introduction, I will examine the current philosophical landscape about biological individuality, and show how the contributions gathered in this special issue address these five objections. Overall, the aim of this issue is to offer a more diverse, unifying, (...) and scientifically informed conception of what a biological individual is. (shrink)

There is currently a great debate about whether the holobiont, i.e. a multicellular host and its residential microorganisms, constitutes a biological individual. We propose that resident microorganisms have a general and important role in the individuality of the host organism, not the holobiont. Drawing upon the Equilibrium Model of Immunity, we argue that microorganisms are scaffolds of immune capacities and processes that determine the constituency and persistence of the host organism. A scaffolding perspective accommodates the contingency and heterogeneity of resident (...) microorganisms while accounting for their necessity and unifying contributions to host individuality. In our symbiotic view of life, holobionts may not be organisms or units of selection, but macroorganisms cannot persist nor function as individuals without their scaffolding microorganisms. (shrink)

Evolutionary Transitions in Individuality have been responsible for the major transitions in levels of selection and individuality in natural history, such as the origins of prokaryotic and eukaryotic cells, multicellular organisms, and eusocial insects. The integrated hierarchical organization of life thereby emerged as groups of individuals repeatedly evolved into new and more complex kinds of individuals. The Social Protocell Hypothesis proposes that the integrated hierarchical organization of human culture can also be understood as the outcome of an ETI—one that produced (...) a “cultural organism” from a substrate of socially learned traditions that were contained in growing and dividing social communities. The SPH predicts that a threshold degree of evolutionary individuality would have been achieved by 2.0–2.5 Mya, followed by an increasing degree of evolutionary individuality as the ETI unfolded. We here assess the SPH by applying a battery of criteria—developed to assess evolutionary individuality in biological units—to cultural units across the evolutionary history of Homo. We find an increasing agreement with these criteria, which buttresses the claim that an ETI occurred in the cultural realm. (shrink)

A crucial question for a process view of life is how to identify a process and how to follow it through time. The genidentity view can contribute decisively to this project. It says that the identity through time of an entity X is given by a well-identified series of continuous states of affairs. Genidentity helps address the problem of diachronic identity in the living world. This chapter describes the centrality of the concept of genidentity for David Hull and proposes an (...) extension of Hull’s view to the ubiquitous phenomenon of symbiosis. Finally, using immunology as a key example, it shows that the genidentity view suggests that the main interest of a process approach is epistemological rather than ontological and that its principal claim is one of priority, namely that processes precede and define things, and not vice versa. (shrink)

Biological individuals are usually defined by evolutionists through a reference to natural selection. This article looks for a concept of individuality that would hold at the same time for organisms and for communities or ecosystems, the latter being unaffected by natural selection. In the wake of Simon’s notion of “quasi-independence,” I elaborate a concept of “weak individuality” defined by probabilistic connections between sub-entities, read off our knowledge of their interactions. This formal scheme of connections allows one to infer what are (...) the individuals in the domain addressed by the theory of the interactions. The article argues that if ecosystems do not have strong individuality, they still possess a weak individuality, ecological theories providing the values of the variables in the formula for individuality. (shrink)

Criticisms of the “container” model of pregnancy picturing female and embryo as separate entities multiply in various philosophical and scientific contexts during the last decades. In this paper, we examine how this model underlies received views of pregnancy in evolutionary biology, in the characterization of the transition from oviparity to viviparity in mammals and in the selectionist explanations of pregnancy as an evolutionary strategy. In contrast, recent evo-devo studies on eutherian reproduction, including the role of inflammation and new maternal cell (...) types, gather evidence in favor of considering pregnancy as an evolved relational novelty. Our thesis is that from this perspective we can identify the emergence of a newhistoricalindividual in evolution. In evo-devo, historical units are conceptualized as evolved entities which fulfill two main criteria, their continuous persistence and their non-exchangeability. As pregnancy can be individuated in this way, we contend that pregnant females are historical individuals. We argue that historical individuality differs from, and coexists with, other views of biological individuality as applied to pregnancy (the physiological, the evolutionary and the ecological one), but brings forward an important new insight which might help dissolve misguided conceptions. (shrink)

This paper presents what we call ‘Hegel's philosophy of biology’ to a target audience of both Hegel scholars and philosophers of biology. It also serves to introduce a special issue of theHegel Bulletinentirely dedicated to a first mapping of this yet to be explored domain of Hegel studies. We submit that Hegel's philosophy of biology can be understood as a radicalization of the Kantian approach to organisms, and as prefiguring current philosophy of biology in important ways, especially with regard to (...) the nature of biological organization, the role of teleology in biological explanation, and the relation between life and cognition. (shrink)

According to the species-as-individuals thesis(hereafter S-A-I), species are cohesive entities. Barker and Wilson recently pointed out that the type of cohesion exhibited by species is fundamentally different from that of organisms (paradigmatic individuals), suggesting that species are homeostatic property cluster kinds. In this article, I propose a shift in how to approach cohesion in the context of S-A-I: instead of analyzing the different types of cohesion and questioning whether species have them, I focus on the role played by cohesion in (...) the identity of individuals. This shift allows us to recognize why cohesion matters to S-A-I, as well as to reconceive the analogy between species and organisms (paradigmatic individuals), and also allows us to highlight the context sensitivity of both ‘‘cohesion’’ and ‘‘individuals.’’ From this perspective, I identify two problems in Barker and Wilson’s argumentation. Firstly, the authors fail to recognize that species are individuals even if they do not have the same type of cohesion that organisms have. Secondly, their argument relies on a misinterpretation of S-A-I. I conclude that species cohesion is still best framed as a feature of species individuality rather than a feature of species as homeostatic property cluster kinds. The arguments presented here contribute to the re-articulation and reevaluation of S-A-I in the face of contemporary discussions. (shrink)

One of Leibniz’s most original ideas is his conception of the living individual as a hierarchical network of living beings whose relationships are essential to the proper functioning of its organic body. This idea is also valid to explain any existing order in nature that depends on the set of relationships of living beings that inhabit it. Both ideas are present in the conception of the natural world that Leibniz presents in his Monadology through his idea of biological infinitism. According (...) to this idea, nature consists of infinite theatres where living beings unfold their vital functions. Through this idea Leibniz defines both the biological complexity of nature and the living individual, which is in turn a portion of nature that unfolds from an infinite set of inferior living beings. The thesis that I defend in this work is that this Leibnizian understanding of the living individual and the natural complexity that includes infinite hierarchical levels of individuality has a marked ecological sense, as we would say today. This Leibnizian metaphysics of individuality that we could call biological is also interesting in light of the recent studies in the philosophy of biology. (shrink)

Following a previous elaboration of the concept of weak individuality and some examples of its instances in ecology and biology, the article focuses on general features of the concept, arguing that in any ontological field individuals are understood on the basis of our knowledge of interactions, through the application of these general formulas for extracting individuals from interactions. Then, the specificities of the individuality in the sense of this weak concept are examined in ecology; I conclude by addressing the differences (...) between ecosystems and organisms as they appear in the viewpoint of such concept. (shrink)