• Mariscal C. & Doolittle W.F. Minor Revisions. “Life and Life Only: A Radical Alternative to Life Definitionism” Synthese
    Abstract: To date, no definition of life has been unequivocally accepted by the scientific community. In frustration, some authors advocate alternatives to standard definitions. These include using a list of characteristic features, focusing on life’s effects, or categorizing biospheres rather than life itself; treating life as a fuzzy category, a process or a cluster of contingent properties; or advocating a ‘wait-and-see’ approach until other examples of life are created or discovered. But these skeptical, operational, and pluralistic approaches have exacerbated the debate, rather than settling it. Given the failure of even these approaches, we advocate a new strategy. In this paper, we reverse the usual line of reasoning and argue that the “life problem” arises from thinking incorrectly about the nature of life. Scientists most often conceptualize life as a class or kind, with earthly life as a single instance of it. Instead, we advocate thinking about Earth’s Life (with a capital ‘L’) as an individual, in the way that species are now thought to be. In this view, Life is monophyletic clade that originated with a Last Universal Common Ancestor (LUCA), and includes all its descendants. We can continue to use the category ‘life’ (lower case ‘l’) pragmatically to refer to similarities between various phenomena and Life. But the relevant similarities are a matter of debate, not discovery. The search for other life in the Universe, then, is merely a search for entities that resemble parts of Life in whatever sense astrobiologists find most appealing (e.g. metabolism, evolution, information, etc.). This does not mean that the search for evolved complexity elsewhere in the universe or its creation in the lab are futile endeavours, only that debates over what is or is not alive are. Ironically, finally abandoning the concept ‘life’ may make our searches for evolved complexity more fruitful. We explain why.
  • Mariscal, C. & Fleming L.Z. Forthcoming. “Why We Should Care About Universal Biology”
    Abstract: Our understanding of the universe has grown rapidly in recent decades. We’ve discovered evidence of water in nearby planets, discovered planets outside our solar system, mapped the genomes of thousands of organisms, and probed the very origins and limits of life. The scientific perspective of life-as-it-could-be has expanded in part by research in astrobiology, synthetic biology, and artificial life. In the face of such scientific developments, we argue there is an ever-growing need for universal biology, life-as-it-must-be, the multidisciplinary study of non-contingent aspects of life as guided by biological theory and constrained by the universe. We present three distinct, but connected ways of universalizing biology—with respect to characterizing aspects of life everywhere, with respect to the explanatory scope of biological theory, and with respect to extending biological insights to the structure of nonbiological entities. For each of these, we sketch the theoretical goals and challenges, as well as give examples of current research that might be labeled universal biology.
  • Mariscal, C. & Petropanagos, A. 2016. “CRISPR as a Driving Force: The Model T of Biotechnology.” Monash Review of Bioethics.
    Abstract: The CRISPR system for gene editing can break, repair, and replace tar- geted sections of DNA. Although CRISPR gene editing has important therapeutic potential, it raises several ethical concerns. Some bioethicists worry CRISPR is a prelude to a dystopian future, while others maintain it should not be feared because it is analogous to past biotechnologies. In the scientific literature, CRISPR is often discussed as a revolutionary technology. In this paper we unpack the framing of CRISPR as a revolutionary technology and contrast it with framing it as a value- threatening biotechnology or business-as-usual. By drawing on a comparison between CRISPR and the Ford Model T, we argue CRISPR is revolutionary as a product, process, and as a force for social change. This characterization of CRISPR offers important conceptual clarity to the existing debates surrounding CRISPR. In particular, conceptualizing CRISPR as a revolutionary technology structures regu- latory goals with respect to this new technology. Revolutionary technologies have characteristic patterns of implementation, entrenchment, and social impact. As such, early identification of technologies as revolutionary may help construct more nuanced and effective ethical frameworks for public policy.
  • Booth, A., Mariscal, C. and Doolittle, W.F., 2016. “The Modern Synthesis in the Light of Microbial Genomics.” Annual Review of Microbiology, 70(1).
    Abstract: We review the theoretical implications of findings in genomics for evolutionary biology since the Modern Synthesis. We examine the ways in which microbial genomics has influenced our understanding of the last universal common ancestor, the tree of life, species, lineages, and evolutionary transitions.
    We conclude by advocating a piecemeal toolkit approach to evolutionary biology, in lieu of any grand unified theory updated to include microbial genomics.
  • Scharf C, Virgo N, Cleaves J, Aono M, Aubert N, Aydinoglu A, Barahona A, Barge L, Benner S, Brasser P, Chandru K, Butch C, Cronin L, Danielache S, Hernlund J, Hut P, Ikegami T, Kimura J, Kobayashi K, Mariscal C, McGlynn S, Menard B, Packard N, Pascal R, Pereto J, Rajamani S, Smith E, Switzer C, Takai K, Tian F, Ueno Y, Voytek M, Witkowski O, Yabuta H. 2015. A Strategy For Origins Of Life Research. Astrobiology Dec 1;15(12):1031-42.

  • Powell R, Mariscal C. 2015. “Convergent Evolution as Natural Experiment: The Tape of Life ReconsideredR. Soc. Interface
    Abstract: Stephen Jay Gould argued that replaying the ‘tape of life’ would result in radically different evolutionary outcomes. Recently, biologists and philosophers of science have paid increasing attention to the theoretical importance of convergent evolution—the independent origination of similar biological forms and functions—which many interpret as evidence against Gould’s thesis. In this paper, we examine the evidentiary relevance of convergent evolution for the radical contingency debate. We show that under the right conditions, episodes of convergent evolution can constitute natural experiments that support inferences regarding the counterfactual stability of macroevolutionary outcomes. However, we argue that proponents of convergence have problematically lumped causally heterogeneous phenomena into a single evidentiary basket, in effect treating all convergent events as if they are of equivalent theoretical import. As a result, the ‘critique from convergent evolution’ fails to engage with key claims of the radical contingency thesis. To remedy this, we develop ways to break down the heterogeneous set of convergent events along several dimensions based on the nature of the generalizations they support. Adopting this more nuanced approach to convergent evolution allows us to differentiate iterated evolutionary outcomes that are probably common among alternative evolutionary histories and subject to law-like generalizations, from those that do little to undermine, and may even support, the Gouldian view of life.
  • Mariscal, C. 2015 “Universal Biology: Assessing Universality from a Single Example” In: Dick, S.J. (ed.), The Impact of Discovering Life Beyond Earth, Cambridge: Cambridge University Press.
  • Mariscal C, Doolittle WF. 2015 Eukaryotes first: how could that be? Phil. Trans. R. Soc. B 370: 20140322.
    Abstract: In the half century since the formulation of the prokaryote : eukaryote dichotomy, many authors have proposed that the former evolved from something resembling the latter, in defiance of common (and possibly common sense) views. In such ‘eukaryotes first’ (EF) scenarios, the last universal common ancestor is imagined to have possessed significantly many of the complex characteristics of contemporary eukaryotes, as relics of an earlier ‘progenotic’ period or RNAworld. Bacteria and Archaea thus must have lost these complex features secondarily, through ‘streamlining’. If the canonical three-domain tree in which Archaea and Eukarya are sisters is accepted, EF entails that Bacteria and Archaea are convergently prokaryotic.We ask what this means and how it might be tested.