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In recent years, the explanatory term "scaffold" has been gaining prominence in evolutionary biology. This notion has a long history in other areas, in particular, developmental psychology. In this paper, we connect these two traditions and identify a specific type of explanatory strategy shared between them, namely scaffolding explanations. We offer a new definition of "scaffold" anchored in the explanatory practices of evolutionary biologists and developmental psychologists that has yet to be clearly articulated. We conclude by offering a systematic overview of the various dimensions of scaffolding explanations that further suggests both their usefulness and range of application. [ABSTRACT FROM AUTHOR]

The transition to multicellularity is perhaps the best-studied of the “major evolutionary transitions”. It has occurred independently multiple times within the eukaryotes alone, and multicellular organisms comprise virtually the entirety of Earth’s macrobiota. However, the theoretical framework used to study the major evolutionary transitions does not neatly accommodate the evolution of complex multicellularity as a process distinct from the evolution of multicellularity more generally. Here, I attempt to fill this explanatory gap. I will first give an overview of research on the major evolutionary transitions, focusing on multicellularity, and demonstrate that the theoretical framework so far utilised does not provide us with sufficient conceptual tools to explain crucial phenomena that call for explanation, such as the evolution of organs and organ systems. I will then discuss our current understanding of early metazoan evolution as paradigmatically exemplifying the evolution of complex organisation in a multicellular system, specifically regarding three core processes enabling it, namely modularisation, subfunctionalisation, and integration, allowing the provision of a general account of the evolution of complex from simple multicellularity that is potentially applicable to other such cases such as the evolution of land plants. This paves the way for a revised account of major evolutionary transitions which incorporates the evolution of complex organismal traits following the evolution of minimal autonomous reproducers while marking a shift of emphasis from reproducers to organisms. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The paper links discussions of two topics: biological individuality and the simplest forms of mentality. I discuss several attempts to locate the boundary between metabolic activity and 'minimal cognition.' I then look at differences between the kinds of individuality present in unicellular life, multicellular life in general, and animals of several kinds. Nervous systems, which are clearly relevant to cognition and subjectivity, also play an important role in the form of individuality seen in animals. The last part of the paper links these biological transitions to the evolutionary history of subjective experience. [ABSTRACT FROM AUTHOR]

Microbes are generally thought of as unicellular organisms, but we know that many microbes live as parts of biofilms-complex, surface-attached microbial communities numbering millions of cells. Some authors have recently argued in favour of reconceiving biofilms as biological entities in their own right. In particular, some have claimed that multispecies biofilms are evolutionary individuals (Doolittle in Biol Philos 28:351-378, ; Ereshefsky and Pedroso in PNAS USA 112(33): 10126-10132 ). Against this view, I defend the conservative consensus that selection acts primarily upon microbial cells. [ABSTRACT FROM AUTHOR]

We argue that the transition from unicellular to multicellular (MC) systems raises important conceptual challenges for understanding agency. We compare several MC systems (from bacterial swarms to colonies and plants, and to lower metazoans) displaying different forms of collective behavior, and we analyze whether these actions can be considered organismically integrated and attributable to the whole. We distinguish between a 'constitutive' and an 'interactive' dimension of organizational complexity, and we argue that MC agency requires a radical entanglement between the related processes which we call 'the constitutive-interactive closure principle'. We explain in detail that this is not possible without a regulatory center functionally integrating the two dimensions, and we also argue that, in turn, this type of regulation would not be possible without a special type of organization between the cells required for the development and maintenance of systems capable of integrated behavior. [ABSTRACT FROM AUTHOR]

In this paper we explore the organizational conditions underlying the emergence of organisms at the multicellular level. More specifically, we shall propose a general theoretical scheme according to which a multicellular organism is an ensemble of cells that effectively regulates its own development through collective (meta-cellular) mechanisms of control of cell differentiation and cell division processes. This theoretical result derives from the detailed study of the ontogenetic development of three multicellular systems ( Nostoc punctiforme, Volvox carteri and Strongylocentrotus purpuratus) and, in particular, of their corresponding cell-to-cell signaling networks. The case study supports our claim that a specific type of functional integration among the cells of a multicellular ensemble (namely, a regulatory control system consisting in several inter-cellular mechanisms that modulate epigenesis and whose operation gets decoupled from the intra-cellular metabolic machinery), is required for it to qualify as a proper organism. Finally, we argue why a multicellular system exhibiting this type of functionally differentiated and integrated developmental organization becomes a self-determining collective entity and, therefore, should be considered as a second-order autonomous system. [ABSTRACT FROM AUTHOR]

Inclusive fitness theory was not originally designed to explain the major transitions in evolution, but there is a growing consensus that it has the resources to do so. My aim in this paper is to highlight, in a constructive spirit, the puzzles and challenges that remain. I first consider the distinctive aspects of the cooperative interactions we see within the most complex social groups in nature: multicellular organisms and eusocial insect colonies. I then focus on one aspect in particular: the extreme redundancy these societies exhibit. I argue that extreme redundancy poses a distinctive explanatory puzzle for inclusive fitness theory, and I offer a potential solution which casts coercion as the key enabler. I suggest that the general moral to draw from the case is one of guarded optimism: while inclusive fitness is a powerful tool for understanding evolutionary transitions, it must be integrated within a broader framework that recognizes the distinctive problems such transitions present and the distinctive mechanisms by which these problems may be overcome. [ABSTRACT FROM AUTHOR]