Russell Powell

Recent work on inheritance systems can be divided into inclusive conceptions, according to which genetic and non-genetic inheritance are both involved in the development and transmission of nearly all animal behavioral traits, and more demanding conceptions of what it takes for non-genetic resources involved in development to qualify as a distinct inheritance system. It might be thought that, if a more stringent conception is adopted, homologies could not subsist across two distinct inheritance systems. Indeed, it is commonly assumed that homology relations cannot survive a shift between genetic and cultural inheritance systems, and substantial reliance has been placed on that assumption in debates over the phylogenetic origins of hominin behavioral traits, such as male-initiated intergroup aggression. However, in the homology literature it is widely accepted that a trait can be homologous—that is, inherited continuously in two different lineages from a single common ancestor—despite divergence in the mechanisms involved in the trait’s development in the two lineages. In this paper, we argue that even on an extremely stringent understanding of what it takes for developmental resources to form a separate inheritance system, homologies can nonetheless subsist across shifts between distinct inheritance systems. We argue that this result is a merit of this way of characterizing what it is to be an inheritance system, that it has implications for adjudicating between alternative accounts of homology, and that it offers an important cautionary lesson about how to reason with the homology concept, particularly in the context of cultural species

Synthetic biology is an emerging discipline that aims to apply rational engineering principles in the design and creation of organisms that are exquisitely tailored to human ends. The creation of artificial life raises conceptual, methodological and normative challenges that are ripe for philosophical investigation. This special issue examines the defining concepts and methods of synthetic biology, details the contours of the organism–artifact distinction, situates the products of synthetic biology vis-à-vis this conceptual typology and against historical human manipulation of the living world, and explores the normative implications of these conclusions. In addressing the challenges posed by emerging biotechnologies, new light can be thrown on old problems in the philosophy of biology, such as the nature of the organism, the structure of biological teleology, the utility of engineering metaphors and methods in biological science, and humankind’s relationship to nature

Any serious ethical discussion of the enhancement of human nature must begin with a reasonably accurate picture of the causal-historical structure of the living world. In this Comment, I show that even biologically sophisticated ethical discussions of the biomedical enhancement of species and speciel natures are susceptible to the kind of essentialistic thinking that Lewens cautions against. Furthermore, I argue that the same evolutionary and developmental considerations that compel Lewens to reject more plausible conceptions of human nature pose equally serious problems for some prominent critiques of biomedical enhancement that presuppose the existence of a “given” biological potential that can be distorted by agentic cultural influences

Stephen Jay Gould argued that replaying the “tape of life” would result in a radically different evolutionary outcome. Some biologists and philosophers, however, have pointed to convergent evolution as evidence for robust replicability in macroevolution. These authors interpret homoplasy, or the independent origination of similar biological forms, as evidence for the power of natural selection to guide form toward certain morphological attractors, notwithstanding the diversionary tendencies of drift and the constraints of phylogenetic inertia. In this paper, I consider the implications of homoplasy for the debate over the nature of macroevolution. I argue that once the concepts of contingency and convergence are fleshed out, it becomes clear that many instances of homoplasy fail to negate Gould’s overarching thesis, and may in fact support a Gouldian view of life. My argument rests on the distinction between parallelism and convergence, which I defend against a recent challenge from developmental biology. I conclude that despite the difficulties in defining and identifying parallelism, the concept remains useful and relevant to the contingency controversy insofar as it underscores the common developmental origins of iterated evolution

The precautionary principle (“the Principle”) has been widely embraced as the new paradigm for contending with biological and environmental risk in the context of emerging technologies. Increasingly, it is being incorporated into domestic, supranational, and international legal regimes as part of a general overhaul of health and environmental regulation.1 Codifications of the Principle typically are vague, with their content intentionally left for scholars to debate, decision makers to interpret, and the courts to flesh out through case law. Generally speaking, the Principle holds that scientific uncertainty will not be a bar to preventive regulatory action, and that decision makers should err on the side of ..

Many philosophers invoke the "wisdom of nature" in arguing for varying degrees of caution in the development and use of genetic enhancement technologies. Because they view natural selection as akin to a master engineer that creates functionally and morally optimal design, these authors tend to regard genetic intervention with suspicion. In Part II, we examine and ultimately reject the evolutionary assumptions that underlie the master engineer analogy (MEA). By highlighting the constraints on ordinary unassisted evolution, we show how intentional genetic modification can overcome many of the natural impediments to the human good. Our contention is that genetic engineering offers a solution that is more eff icient, reliable, versatile, and morally palatable than the lumbering juggernaut of Darwinian evolution. In Part III, we evaluate a recent attempt to ground precautionary enhancement heuristics in adaptive etiology. Our problem with this approach is two-fold: first, it is based on the same "strong adaptationist" interpretation of evolution that motivates the flawed MEA, and second, the etiological concept of function on which it relies provides indirect and potentially misleading information about the likely consequences of genetic intervention. We offer instead enhancement criteria based on causal relationships in ontogeny. We conclude that rather than grounding a presumption against deliberate genetic modification, the causal structure of the living world gives us good moral reason to pursue it

A common worry about the genetic engineering of human beings is that it will reduce human genetic diversity, creating a biological monoculture that could not only increase our susceptibility to disease but also hasten the extinction of our species. Thus far, however, the evolutionary implications of human genetic modification remain largely unexplored. In this paper, I consider whether the widespread use of genetic engineering technology is likely to narrow the present range of genetic variation, and if so, whether this would in fact lead to the evolutionary harms that some authors envision. By examining the nature of biological variation and its relation to population immunity and evolvability, I show that not only will genetic engineering have a negligible impact on human genetic diversity, but also that it will be more likely to ensure rather than undermine the health and longevity of the human species

There is a tendency in both scientific and humanistic disciplines to think of biological evolution in humans as significantly impeded if not completely overwhelmed by the robust cultural and technological capabilities of the species. The aim of this article is to make sense of and evaluate this claim. In Section 2 , I flesh out the argument that humans are ‘insulated’ from ordinary evolutionary mechanisms in terms of our contemporary biological understandings of phenotypic plasticity, niche construction, and cultural transmission. In Section 3 , I consider two obvious objections to the above argument based on the growing literatures related to gene-culture coevolution and recent positive selection on the human genome, as well as a pair of less common objections relating to the connection between plasticity, population size and evolvability. In Section 4 , I argue that both the ‘human evolutionary stasis argument’ and its various detractor theories are premised on a fundamental conceptual flaw: they take evolutionary stasis for granted, since they fail to conceive of stabilizing selection as a type of evolution and drift as a universal tendency that dominates in the absence of selection. Without the continued operation of natural selection, the very properties that are purported to reduce the evolutionary response to selection in humans would themselves drift into non-functionality. I conclude that properly conceived, biological evolution is a permanent and ineradicable fixture of any species, including Homo sapiens

A number of authors have pointed to “convergent evolution” as evidence for the central role of natural selection in shaping predictable trajectories of macroevolution. However, there are numerous conceptual and empirical difficulties that arise in broadly appealing to the frequency of homoplasy as evidence for a non-contingently constrained adaptational design space. Most important is the need to distinguish between convergent (externally constrained) and parallel (internally constrained) evolution, and to consider how the respective frequencies of these significantly different sources of homoplasy affect a strong adaptationist view of life. In this paper, I critically evaluate Simon Conway Morris’s use of the homoplasy literature to support his argument for a non-contingent, counterfactually stable account of macroevolutionary pattern. In so doing, I offer a conception of parallelism which avoids the charge that it differs from convergence merely in degree and not in kind. I argue that although organisms sharing a homoplastic trait will also share varying degrees of homology, it is the underlying developmental homology with respect to the generators directly causally responsible for the homoplastic event that defines parallel evolution and non-arbitrarily distinguishes it from convergence. The notion of “screening-off” is used to distinguish the proximal generators of a homoplastic trait from its more distal genetic causes (such as a master control gene).

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.

Traditional conservative arguments against the possibility of moral progress relied on underevidenced assumptions about the limitations of human nature. Contemporary thinkers have attempted to fill this empirical gap in the conservative argument by appealing to evolutionary science. Such “evoconservative” arguments fail because they overstate the explanatory reach of evolutionary theory. We maintain that no adequate evolutionary explanation has been given for important features of human morality, namely cosmopolitan and other “inclusivist” moral commitments. We attribute these evolutionarily anomalous features to a capacity for open-ended normativity, which presents a serious obstacle to theorists who wish to draw substantive moral and political lessons from human evolutionary history