International Society for History, Philosophy, and Social Studies of Biology


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Program

WEDNESDAY, JULY 8  /  09:00 - 10:30  /  DS-R515
Organized session / standard talks
Explaining a four billion year old phenomenon (1): Life and its chemical origins
Organizer(s):

Christophe Malaterre (Université du Québec à Montréal, Canada); Carol Cleland (University of Colorado Boulder, United States)

Life’s originated on Earth around four billion years ago. How do scientists go about explaining this ancient event for which no telling traces remain? Several contemporary theories currently coexist, some favouring metabolism-first approaches, others genes-first approaches. All aim at bridging the gap from non-living matter to living matter. In this session and round-table, three philosophers and two scientists investigate some of the key problems that arise in origins of life research: What considerations ground the distinction between metabolism-first and genes-first theories? Is the origin of life distinct from the origin of evolution? How does chemical evolution relate to biological evolution? What role does thermodynamics play in chemical evolution? How do scientists test hypotheses about the origins of life? And do they?


A legacy of Aristotle: Metabolism-first vs. genes-first theories of the origins of life

Carol Cleland (University of Colorado Boulder, United States)

There is widespread agreement among biologists and philosophers of biology that two characteristics of familiar life are foundational: the capacity to (O) self-organize and maintain self-organization (aka metabolize) for an extended period of time and (R) reproduce and (in light of Darwin’s theory) transmit to progeny adaptive characteristics. Precursors of O and R are found in the writings of Aristotle, who identified “nutrition” (O) and “reproduction” (R) as essential to life, debated which was more fundamental, and argued that both involve what (from a contemporary perspective) amounts to a peculiar form of causation: internally generated, goal-directed causal processes. Contemporary theories of the origins of life echo Aristotle in privileging either metabolism or (genetic-based) reproduction as essential to life. Like Aristotle, they struggle with making sense of the nature of the causation involved. Tacit appeals to causal processes that are self-generating and goal-directed are routine in discussions of the origins of life, e.g., the “spontaneous assembly” of chemically improbable, primordial biomolecules, such as peptides or small RNA molecules, from more basic molecular components, and the “emergence” of proto-organisms from complex autocatalytic, chemical reaction systems. These notions of causation are difficult to make sense of in terms of ordinary, undirected causal processes familiar from the physical sciences. This raises the question as to whether a more fruitful account of the origins of life might be achieved by abandoning the theoretical framework for biology bequeathed to us by Aristotle. Such a move would parallel the abandonment of Aristotle’s ideas in chemistry and physics, which were followed by rapid advances in scientific understanding. Indeed, viewed from a historical perspective, it is somewhat surprising that biology is still so closely wedded to Aristotelian ideas.


The plague of equilibrium in modern origin of life theories

Elizabeth Griffith (University of Maryland, United States)

One overarching problem plaguing leading origin of life theories is the transition from non-living components to an independent, nominally living, system. Life is known to be a highly out-of-equilibrium system. Our cells maintain gradients through actively pumping material into and out of them on a regular basis, thereby avoiding the tendency to achieve equal concentrations of the material in question on both sides of the barrier. In order to transition from non-life to life, thermodynamic equilibrium must be overcome to ultimately achieve this characteristic disequilibrium. Stemming from their differing levels of analysis, RNA and small molecule (SM) world theories have different problems in this respect. The RNA world stems from a biological level of analysis, originating in the historical discovery of the ribozyme in modern life followed by the extrapolation to the origin of life. Work performed under the premise of the RNA world arguably approaches the transition from non-life to life producing systems that mimic many of the functions of modern life. However, many of these functions still succumb to, or are even dictated by, the principles of thermodynamic equilibrium. In contrast, the SM world stems from a chemical level of analysis and hence concentrates on self-organized and self-propagating chemical systems. Through this concentration on catalysis, SM world studies have focused on the problem of equilibrium, even achieving propagating disequilibrium through time. However, it is difficult to envision an autocatalytic system propagating through time as an example of early life, suggesting that although disequilibrium is a necessary condition for life, it is not sufficient. In these respects, the RNA world and SM world theories face different problems in regards to the transition from non-life to life, which will be discussed in more detail.


Making sense of "chemical evolution"

Christophe Malaterre (Université du Québec à Montréal, Canada)

The concept of “chemical evolution” aims at explaining how non-living matter has evolved into living matter on the primitive Earth. Endowed with a rich historical legacy, it has come to occupy a central place in scientific debates on the origins of life. It also generates much controversy: for some, it consists in Darwinian evolution applied to chemical systems (Calvin 1961); for others, it is precisely the type of evolution that happened before Darwinian evolution (Joyce 2002, de Duve 2005). Pioneering research in systems chemistry and synthetic biology is fuelling the debate even more by providing radically novel insights into possible prebiotic evolutionary processes like molecular cooperation, the emergence of competition among protocells or the role of simple physical effects in the transition to life (Budin and Szostak 2011). This contribution aims at explicating the concept of “chemical evolution” in the light of such recent advances in origins of life studies. I propose to construe “chemical evolution” as a composite theory that draws upon several evolutionary processes (rather than a single process of natural selection), and I argue that the relative importance of these processes over time helps construing a gradualist transition to biological evolution.