Here we endorse Hull’s replicator/interactor framework as providing the overarching understanding sought by MacCord and Maienschein. We suggest that difficulties in seeing the regeneration of limbs by salamanders and of forest ecosystems after fires as similar evolutionary processes can be overcome in this framework. In generalizing Dawkins’s “selfish gene” perspective, Hull defined natural selection as “a process in which the differential extinction and proliferation of interactors causes the differential perpetuation of the replicators that produced them”. Although genes and bacteria are (...) simultaneously both replicators and interactors, communities and ecosystems are generally only interactors. As reproducers, members of sexual species are intermediate. Within such species, organisms are indeed the interactors whose “differential extinction and proliferation” causes the “differential perpetuation” of replicators. But sexually-reproducing organisms do not individually replicate, persist, or recur as interactors, and in consequence it is only those genes causing an interactor differential that are specifically perpetuated in the long run. Higher-level interactors may seldom if ever reproduce, but their recurrence does enable the “differential perpetuation” of replicators specifically responsible for their “differential extinction and proliferation”. In offering answers to the question “What are the replicators specifically responsible for the differential extinction and proliferation of such higher-level entities?” we hope to unify adaptive regeneration across scales, from organisms to ecosystems. (shrink)

Diverse living systems possess the capacity for regeneration; that is, they can under some circumstances repair, re-produce, and maintain themselves in the face of disturbance or damage. Think of systems as diverse as forests, microbial biofilms, corals, salamanders, hydra, and human skin cells. This capacity is fundamental to life—without it, many biological systems would be too fragile to cope with stress and would frequently collapse—but because it is multiply realized in wildly different living systems at many scales, finding a common (...) understanding may seem futile, and in fact research has proceeded along independent lines. For example, the sciences of organismal regeneration and ecological regeneration appear to have little more than a nominal relationship. Progress towards unification can be made, we think, by turning to evolutionary theory, specifically by synthesizing recent discussions of the evolution of individuals versus collectives with older literature about replicators versus interactors. This allows us to provide a partial answer in response to MacCord and Maienschein’s call for “basic units and mechanisms” of regeneration, relevant when that process is “adaptive.” We argue that the basics of adaptive regeneration can be understood and generalized through a modification of David Hull’s replicator-interactor framework. (shrink)

The basic thesis of Russell Powell’s Contingency and Convergence: Toward a Cosmic Biology of Body and Mind is that law-like evolutionary processes produce humanlike cognitive capacities, rendering such capacities common in the universe. There is an important caveat; key aspects of human cognition, those that undergird cumulative culture, are entirely contingent and likely very rare. To defend this thesis, Powell marshals a wealth of evidence from a variety of disciplines and develops some singular theoretical tools. Unfortunately, at a number of (...) key points in the book Powell simply ignores contradicting evidence and other plausible approaches to thinking about the history of life on our planet. Thus Powell’s argument is, at best, a weak how possibly argument—another Just-So story mixing science with speculation. Nonetheless, the flaws in the book are instructive. They exemplify how a kind of anthropocentrism continues to shape the philosophy of biology and, arguably, biology itself, placing humans at the apex of evolution and demanding that the study of life must ultimately be about us. In effect, Powell offers a rationalization for why we can treat humans as the measure of all things, asserting our continuity with the rest of life on the planet, while at the same time maintaining our uniqueness. Interrogating his argument proves a useful exercise in identifying why this kind of anthropocentrism is implausible. (shrink)

Over the last three decades, studies in microbiology have exposed a world of diverse and dynamic interactions. Through metagenomic sequencing, complex bacterial communities became visible and proved important for many biological phenomena. As a result of discovering the connection between microorganisms and organisms’ survival, the notion of the holobiont has become prominent and has been suggested as a biological individual. The view of the holobiont as an individual, commonly known as the Hologenome Theory, focuses on the interactions and relations between (...) the host and its symbionts in the host’s development and evolution. Today, the holobiont is at the heart of the debate on the nature of the biological individual, a debate which is connected to the same question about the nature of the individual organism. (shrink)

Over the last three decades, studies in microbiology have exposed a world of diverse and dynamic interactions. Through metagenomic sequencing, complex bacterial communities became visible and proved important for many biological phenomena. As a result of discovering the connection between microorganisms and organisms’ survival, the notion of the holobiont has become prominent and has been suggested as a biological individual. The view of the holobiont as an individual, commonly known as the Hologenome Theory, focuses on the interactions and relations between (...) the host and its symbionts in the host’s development and evolution. Today, the holobiont is at the heart of the debate on the nature of the biological individual, a debate which is connected to the same question about the nature of the individual organism. (shrink)

Phenotypic plasticity, or an organism’s capacity to change its phenotype in response to environmental variation, is a pervasive—perhaps even ubiquitous—feature of the biological world. Accordingly, plasticity research suggests serious implications for biological theory, including evolutionary theory. The theoretical implications of plasticity have growing support from empirical literature documenting the range, extent, and adaptiveness of plasticity. However, the empirical evidence for particular instances of plasticity has still not been adequately scrutinized by biologists or philosophers. After reviewing some important conceptual and theoretical (...) background information, this paper synthesizes some past discussions of the methodology of plasticity studies and provides some novel methodological guidance for plasticity researchers. My conclusion is that not all plasticity studies should carry the same weight: there are patterns we can identify in the features of such studies that should contribute to their credibility. In particular, I argue that some types of organisms and some types of plastic phenotypes are more conducive to the empirical study of plasticity than others. (shrink)

Elliott Sober can be understood as advancing two distinct arguments that similarly conclude that evolutionary theory does not say that Scriven’s infamous twins have the same fitness, despite the twins’ identical genotypes and phenotypes. The first argument relies on denying that evolutionary theory can say that the twins are in the same environment, and the second relies on asserting an epistemic access asymmetry between token fitness and trait fitness. Motivated by good reasons, I respond to both of these arguments by (...) showing that the theory of evolution by natural selection has adequate means for determining whether the twins are in the same environment via causal-probabilistic decomposition, and that equivalence in fitness can be asserted even from a partial theory of fitness, regardless of epistemology. Finally, I point out an absurd result regarding genetic drift as indiscriminate sampling that follows if Sober’s conclusion is true. (shrink)

Within the philosophy of biology, Michael Scriven’s twins has become a well-known thought experiment, due to its being the impetus for various lines of discussion concerning the contentious definition of evolutionary fitness, the distinction between natural selection and genetic drift, and evolutionary environments. As one version of the story goes: two twins who, ex hypothesi, are genotypically and phenotypically the same are located side by side on a mountain. An unfortunate event ensues whereby a lightning strike kills one of the (...) twins, whilst the other twin survives. For added disparity, the surviving twin goes on to proliferate extensively by bearing a large number of offspring. Importantly, it is usually inferred, from the stipulations of the thought experiment, that the twins also have the same evolutionary fitness. The inference is important because the premise that the twins have the same fitness paves way for a number of influential views; most notably, it has led to the propensity interpretation of evolutionary fitness. (shrink)