While the winds of change are stirring across evolutionary theory, there is larger, long-term current of change approaching from chemistry. The chemists have a claim that chemical evolution is the real basis of evolution while species evolution is a secondary process (Williams & Frausto da Silva 2006; Williams & Rickaby 2012). At the same time there are many origin-of-life researchers who are studying how prebiotic chemistry could lead to life, and they are making rapid progress. They are effectively studying a chemical evolution that occurred for hundreds of millions of years before the first cell or before any life as we know it. And some of these same researchers see the species concept as a secondary phenomenon to the biosphere as a whole (Smith & Morowitz 2016).
Most of us assume that chemistry is what living organisms use for their lives. This suite of ideas from chemical evolution, biosphere primacy, and prebiotic chemistry sees evolution as a big, changing current driven by energy that gets its chemical energy organized and partitioned by different forms of life. Chemical evolution is seen to be primary, and the evolution of organisms or species is secondary. These ideas are introduced here as a way of underlining the claim that evolutionary theory will soon be forced to grow. They are a further invitation to the opening for a new evolutionary synthesis, an expanded and more encompassing theory.
These trends show up in the challenge to Darwinian evolutionary theory in the form of a claim by many that only the biosphere (or sometimes separate ecosystems as relatively independent) is the proper unit of life. An outstanding new book on the origin of life (Smith & Morowitz 2016) says it clearly in its title that the origin of life is the biosphere as “the emergence of the fourth geosphere” (to go along with rock, water, and air or lithosphere, hydrosphere, and atmosphere). As the physicist Lee Smolin notes, the notion of a living thing as primary is to invite the absurd notion that an animal, say a camel, could exist by itself anywhere in the universe (Smolin 1997, p. 145). Smith and Morowitz clarify the biosphere as “a set of patterns maintained by processes, and patterns of processes, and not merely a collection of ‘living things’” (p. 11). And to make it clear: “the biosphere as a whole is the correct level of aggregation from which to define the nature of the living state” (p. 11). Forget organisms and species; the biosphere is where the action is.
Within this frame Smith and Morowitz show how the early earth could convert the simple bulk chemistry of the three earlier geospheres into the relatively simple chemistry of universal metabolism whose flows are used or divided up among all living things.
The chemists Williams, Frausto da Silva, and Rickaby focus on how chemistry has seen changes in its types of reactions over earth history that have allowed life and its own evolution. They see successive waves of types of prevalent reactions where earlier types facilitate later types. For example, the early reductive chemistry that allowed anaerobic bacteria led to the production of free oxygen which then led to an era of chemistry hospitable to aerobic organisms. Each of these eras are “chemotypes” or types of chemistries, or even really types of environments, that grow to a point where a new chemotype emerges so that new species then become possible. They, in fact, come up with principles of chemical evolution. Each of these chemotypes shows some of the principles they uncover such as: 1) ever new sources of energy, 2) always additional chemicals from the table of elements, 3) new types of compartments for new types of chemical reactions, 4) increasing presence of oxidized chemicals, 5) the growth of the cellular organisation between compartments in space with time, and 6) newer and faster modes of organization or communication (Williams & Frausto da Silva 2006, pp. 426-7). The conceptualization of evolution as a chemical process is formidable, but I find no responses from biologists as to how to integrate their respective views. It remains a challenge, or better, a source for insights in how to re-integrate evolutionary theory.
Aside from these two broad chemical and somewhat counter-biological formulations of evolution, there are the hundreds of researchers making fast advances in origin-of-life studies. In looking over books covering this bubbling field for the general reader, I don’t see a lot to recommend. Maybe Adam Rutherford’s Creation (2014). Or maybe The Nature of Life by Mark Bedau and Carol Cleland (2010), which is a collection from different authors. When, however, one looks at specific journal articles that report new, specific studies, one is struck by the detail and the chemical novelties that each make the emergence of protocells more plausible. There is a book there for someone to write in the near future.
For now I can mention a few of the topics of this research in a way that shows its richness and that hints at what might lead to some principles to be formulated later.
An early challenge was whether the early earth can provide for the production of the common molecules that are found in life – the sugars and amino acids. This has now been demonstrated in many ways starting with the famous Miller-Urey experiment of 1952 where electric sparks to imitate lightning in a test tube of carbon dioxide and ammonia and water yielded a rich diversity of life’s basic molecules. The challenge since this work has been to show how these common molecules could under plausible early earth environments then form long chains such as are found in proteins or nucleic acids. This too has now been shown in plausibility experiments. Waechtershaeuser (2012) sees this chain growth happening by transition metal catalysis. Egel (2014) sees this happening in colloids or chemical blobs. Damer and Deamer (2015) see this happening by dehydration reactions by evaporation on the edge of volcanic pools.
Other plausibility arguments multiply. Shapiro (2007) sees the power of autocatalytic loops [chemicals that speed the reaction of other chemicals which are linked in reaction cycles with each other] to induce chemical growth. Smith and Morowitz (2016, pp. 36-40) see how early protocells were small ecosystems of chemicals that added innovations to be more stable. Some researchers explore how the initial starter molecules could aggregate rather than be scattered such as by the ocean (Hansma 2014).
Within the studies to elucidate the origin of life a whole new type of chemistry has emerged. Systems chemistry (Von Kiedrowski et al 2010) is a new field that is exploring chemical pathways that are heavily dependent on very local conditions as opposed to just being reactions in solution that were simple changes on a big scale. Local shapes and local molecular forces are types of small effects that can produce unique reaction pathways. And, as the name implies, systems effects show many of the feedback-type mechanisms seen in other examples of complex systems.
Especially intriguing is that many researchers are speaking of how chemicals become selected by within chemical groupings. For example, small collections can be made more or less stable by the contribution of certain component molecular types so that the longevity of collections selects those compounds that promote stability (Egel 2014). Some researchers use the phrase “chemical selection” (Enrique Melendez-Hevia, N. Montero-Gomez & F. Montero 2008, p. 508).
At this point one hears origin-of-life researchers speaking of “chemical evolution” quite often (e.g. Lehn 2013). And this brings the issue back to our focus here on evolutionary theory. Here are two complementary views of “chemical evolution.” The chemists at the top here have a general claim about the chemical evolution of the earth. And the origin-of-life researchers keep finding specific instances of “chemical evolution” that took place during the extended period of hundreds of millions of years before the first cell. So what then is chemical evolution and how is it related to Darwinian evolution? Answers to this question would seem to be very relevant to the issues that evolutionary theory is already experiencing (see previous post). And answers to this question would seem to be able to address the charge that Darwinian evolution spoke to selection without adequately speaking to generation of new living forms (previous post; Reid 2007, p. 15). Chemical evolution in the prebiotic world is clearly about the generation of life.
If evolutionary theory of the Modern Synthesis is already wiggling to be extended as we are seeing, then the growing strength of concepts in chemical evolution and in prebiotic evolution are sure at some point to give an impetus for reform or for a greater integration of evolutionary principles. This is not a problem; this is a win-win opportunity as divergent research offers potentially complementary insights for integration. The more progress made by the origin-of-life researchers, the more likely that the Modern Synthesis for Darwinism will be forced to confront the principles of evolution before the first cell. The evolution before the first cell is likely to have principles of its own but yet share some of those principles with life after the first cell. Accepting two completely separate periods and theories of evolution would be untenable. There is every reason to expect a new source for a push to a new synthesis and to begin to take advantage of it now.
References
Bedau, Mark & C. Cleland. 2010. The Nature of Life: Classical and Contemporary Perspectives from Philosophy and Science. Cambridge University Press.
Damer, Bruce & D. Deamer. 2015. “Coupled Phases and Combinatorial Selection in Fluctuating Hydrothermal Pools: A Scenario to Guide Experimental Approaches to the Origin of Cellular Life.” Life 5: 872-887.
Egel, Richard. 2014. “Origins and Emergent Evolution of Life: The Colloid Microsphere Hypothesis Revisited.” Orig Life Evol Biosph. 44: 87-110.
Hansma, Helen. 2014. “The Power of Crowding for the Origins of Life.” Orig Life Evol Biosph. 44:307-311.
Lehn, Jean-Marie. 2013. “Perspectives in Chemistry–steps toward Complex Matter.” Angewandte Chemie International Edition. 52;2836-2850.
Melendez-Hevia, Enrique, N. Montero-Gomez & F. Montero. 2008. “From prebiotic chemistry to cellular metabolism–The chemical evolution of metabolism before Darwinian natural selection.” Journal of Theoretical Biology 252:505-519.
Miller, Stanley & H. Urey. 1959. “Organic Compound Synthesis on the Primitive Earth,” Science 130(3370):245-251.
Reid, Robert. Biological Emergences: Evolution by Natural Experiment. 2007. MIT Press.
Rutherford, Adam. 2014. Creation: The Origin of Life / The Future of Life. Penguin.
Shapiro, Robert. 2007. “A Simpler Origin for Life.” Scientific American. June. Pp. 129-136. From: Bedau, Mark & C. Cleland. 2010. The Nature of Life: Classical and Contemporary Perspectives from Philosophy and Science. Cambridge UP.
Smith, Eric & H. Morowitz. 2016. The Origin and Nature of Life on Earth: The Emergence of the Fourth Geosphere. Cambridge University Press.
Smolin, Lee. 1997. The Life of the Cosmos. Oxford University Press. p. 145.
Von Kiedrowski, Guenter, S. Otto & P. Herdewign. 2010. “Welcome Home, Systems Chemists!” Journal of Systems Chemistry. 1:1.
Waechtershaeuser, Guenter. 2012. “Origin of Life: RNA World Versus Autocatalytic Anabolist,” The Prokaryotes – Prokaryotic Biology and Symbiotic Associations, pp. 81-8, Rosenberg, Eugene, E. DeLong, E. Stackebrandt, S. Lory & F. Thompson (eds), Springer.
Williams, RJP & J.J.R. Frausto da Silva. 2006. The Chemistry of Evolution: The Development of our Ecosystem. Elsevier.
Williams R. & R. Rickaby. 2012. Evolution’s Destiny: Co-evolving Chemistry of the Environment and Life. The Royal Society of Chemistry.