Abstract
Do trees of life have roots? What do these roots look like? In this contribution, I argue that research on the origins of life might offer glimpses on the topology of these very roots. More specifically, I argue (1) that the roots of the tree of life go well below the level of the commonly mentioned ‘ancestral organisms’ down into the level of much simpler, minimally living entities that might be referred to as ‘protoliving systems’, and (2) that further below, a system of roots gradually dissolves into non-living matter along several functional dimensions. In between non-living and living matter, one finds physico-chemical systems that I propose to characterize by a ‘lifeness signature’. In turn, this ‘lifeness signature’ might also account for a diverse range of biochemical entities that are found to be ‘less-than-living’ yet ‘more-than-non-living’.
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Notes
The term “protoliving system” has been used in origins of life studies with the meaning of rudimentary, primordial -and potentially minimal- living systems (Fox 1991) It is with this meaning that I use the term here. This meaning might be found to be synonymous to that of “protocell” even though protoliving systems do not require, strictly speaking, to be cell-like. Also, the term “protocell” is now often used in synthetic biology with a broader meaning, for instance including systems made out of non-prebiotically compatible compounds or resulting from artificial life research (e.g. Rasmussen et al. 2009) than the initial meaning it had in origins of life studies (e.g. Krampitz and Fox 1969; Stillwell 1980; de Duve 1991).
Such dimensions might correspond to properties of “list-based” definitions or relate to the functioning characteristics of the models involved in “model-based” definitions of life.
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Acknowledgments
An earlier version of this paper was presented at the Perspectives on the Tree of Life workshop, sponsored by the Leverhulme Trust and held in Halifax, July 2009. I am indebted to several participants for valuable comments, and to Maureen O’Malley and John Dupré for providing such a valuable brainstorming platform. I also thank Jacques Reisse of the Université Libre de Bruxelles and Jean Gayon at the Université Paris 1—Panthéon Sorbonne for stimulating discussions, as well as two anonymous referees for their insightful comments. Support from the CNRS interdisciplinary program “Origines des planètes et de la vie” and from the Fondation Louis D. of the Institut de France is gratefully acknowledged.
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Malaterre, C. Lifeness signatures and the roots of the tree of life. Biol Philos 25, 643–658 (2010). https://doi.org/10.1007/s10539-010-9220-8
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DOI: https://doi.org/10.1007/s10539-010-9220-8