VI. Earth Life Emergence: Development of Body, Brain, Selves and Societies
2. The Origins of Life
Deacon, Terrence. Reciprocal Linkage Between Self-organizing processes is Sufficient for Self-reproduction and Evolvability. Biological Theory. 1/2, 2006. (A new journal of theoretical biology from MIT Press.) A sophisticated organic dynamics are laid out whereof life complexifies to selectable stages in the minimum form of autocatalytical, bounded “autocells.” (or UR-cell if you wish.) These primal units are further distinguished by properties of information transfer, metabolism, and bounded containment.
Deamer, David. Assembling Life: How Can Life Begin on Earth and Other Habitable Planets? New York: Oxford University Press, 2019. The veteran UC Santa Cruz origins researches continues his lifelong flow of frontier volumes with ever better retrospective explanations. See also his Origin of Life: What Everyone Needs to Know (Oxford, 2020) for even more insights.
In Assembling Life, David Deamer continues to address how did non-living organic compounds assemble into the first forms of primitive cellular life? What was the source of those compounds and the energy that produced the nucleic acids? Did life begin in the ocean or in fresh water on terrestrial land masses? Deamer describes organic chemicals that were likely to be available in the prebiotic environment and the volcanic conditions that could drive their complexity. In a wider view the goal is to understand how life can begin on any habitable planet.
Deamer, David. First Life and Next Life. Technology Review. May/June, 2009. The University of California, Santa Cruz “research professor of biomolecular engineering” muses that life’s earthly origin might have involved five steps: a source of organic monomers; self-assembly of compartments and protocells; polymer synthesis; evolution of catalysts; and combinatorial chemistry of cellular vesicles. As regnant life, actually its informational capacity, lately reaches self-awareness so as to pass to human agency, a radical new phase can begin of the intentional design of synthetic genomes, cells, and organic forms.
The requirement of variation within a population means that the first life forms capable of evolution could not be random mixtures of replication molecules unable to assemble into discrete entities; instead, they would be systems of interacting molecules encapsulated in something like a cell. (68)
Deamer, David. First Life: Discovering the Connections between Stars, Cells, and How Life Began. Berkeley: University of California Press, 2011. The veteran University of California at Santa Cruz biochemist offers a current survey upon an area that when I began readings some fifty years ago was an inaccessible void. Today organism and cosmos move ever closer together as a unified continuum. Typical chapters include When Did Life Begin?, Energy and Life’s Origins, Self-Assembly and Emergence, Achieving Complexity, and A Grand Simulation of Prebiotic Earth.
This pathbreaking book explores how life can begin, taking us from cosmic clouds of stardust, to volcanoes on Earth, to the modern chemistry laboratory. Seeking to understand life’s connection to the stars, David Deamer introduces astrobiology, a new scientific discipline that studies the origin and evolution of life on Earth and relates it to the birth and death of stars, planet formation, interfaces between minerals, water, and atmosphere, and the physics and chemistry of carbon compounds. Deamer argues that life began as systems of molecules that assembled into membrane-bound packages. These in turn provided an essential compartment in which more complex molecules assumed new functions required for the origin of life and the beginning of evolution. (Publisher)
Deamer, David and Jack Szostak, eds. The Origins of Life. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press, 2010. A premier, current collection with these five sections: Setting the Stage, Components of First Life, Primitive Systems, First Polymers, and Transition to a Microbial World. Its emphasis is more on overt entities, which are seen to arise from a prebiotic conducive chemistry. And even at this early outset, one can observe nature’s recurrent persistence to form distinct, bounded vesicles and protocells.
The advent of systems biology and synthetic biology also changed the way we think about the origin of life. At some point in the pathway leading to life, there must have been a process by which molecular systems were encapsulated in cellular compartments. This understanding is now driving serious efforts to assemble artificial cells using the tools of synthetic biology, in sense attempting to achieve a second origin of life that will tell us much about the first origin. (Editors, vii)
Deamer, David, et al. The First Cell Membranes. Astrobiology. 2/4, 2003. On the tendency of organic macromolecules to self-assemble into and be encapsulated by closed membranous vesicles.
Delaye, Luis and Antonio Lazcano. Prebiological Evolution and the Physics of the Origin of Life. Physics of Life Reviews. 2/1, 2005. This new journal is available online, via Google. The authors contend that understanding life’s origin requires a synthesis of geology, chemistry, biology, astrophysics, theoretical physics, paleontology and philosophy. In this broad context, their hypothesis combines the relatively rapid appearance of chemical replicating, gene-like molecules, possibly in the vicinity of deep-sea vents, along with a consideration of intrinsic self-organizing, emergent systems.
Derr, Julien, et al. Prebiotically Plausible Mechanisms Increase Compositional Diversity of Nucleic Acid Sequences. Nucleic Acids Research. 40/10, 2012. By way of sophisticated theory and experiment, Harvard University biosystem scientists including Irene Chen and Martin Nowak, engage the deepest issue of whether the appearance of such viable replicative biomolecules happened by capriciousness or was due to some innate, independent â€śpredispositionâ€ť at work. Indeed, this ultimate â€śto be or not to beâ€ť question is just lately becoming answerable in actual favor of a primal propensity to cause and give rise to complexifying life and its evolutionary ascent.
During the origin of life, the biological information of nucleic acid polymers must have increased to encode functional molecules (the RNA world). Ribozymes tend to be compositionally unbiased, as is the vast majority of possible sequence space. However, ribonucleotides vary greatly in synthetic yield, reactivity and degradation rate, and their non-enzymatic polymerization results in compositionally biased sequences. While natural selection could lead to complex sequences, molecules with some activity are required to begin this process. Was the emergence of compositionally diverse sequences a matter of chance, or could prebiotically plausible reactions counter chemical biases to increase the probability of finding a ribozyme?
Dokholyan, Nikolay, et al. Expanding Protein Universe and Its Origin from the Biological Big Bang. Proceedings of the National Academy of Sciences. 99/14132, 2002. The microcosm of macromolecular proteins is found to exhibit a universal similarity at different levels of complexity.
With the large number of protein structures identified in the past decades, we have discovered peculiar patterns that nature imprints on protein structural space in the course of evolution. In particular, we have discovered that the universe of protein structures is organized hierarchically into a scale-free network. (14132)
Eukaryogenesis: On the Communal Nature of Precellular States, Ancestral to Modern Life.
For a special, on-going issue of this online journal on the Origin of Life, a University of Copenhagen Biocenter researcher provides a 50 page contribution that stresses an inherent proclivity of biomatter toward such social assemblies. One might imagine that prokaryotes, eukaryotes, and precursor vesicles are moved and guided by these independent, genetic-like forces. See also the author’s chapter “Integrative Perspectives: In Quest of a Coherent Framework for Origins of Life on Earth” in Egel, et al, eds. Origins of Life (Springer, 2011 herein).
This problem-oriented, exploratory and hypothesis-driven discourse toward the unknown combines several basic tenets: (i) a photo-active metal sulfide scenario of primal biogenesis in the porespace of shallow sedimentary flats, in contrast to hot deep-sea hydrothermal vent conditions; (ii) an inherently complex communal system at the common root of present life forms; (iii) a high degree of internal compartmentalization at this communal root, progressively resembling coenocytic (syncytial) super-cells; (iv) a direct connection from such communal super-cells to proto-eukaryotic macro-cell organization; and (v) multiple rounds of micro-cellular escape with streamlined reductive evolution—leading to the major prokaryotic cell lines, as well as to megaviruses and other viral lineages. Hopefully, such nontraditional concepts and approaches will contribute to coherent and plausible views about the origins and early life on Earth. In particular, the coevolutionary emergence from a communal system at the common root can most naturally explain the vast discrepancy in subcellular organization between modern eukaryotes on the one hand and both archaea and bacteria on the other. (Abstract, 170)
Egel, Richard. Origins and Emergent Evolution of Life. Origins of Life and Evolution of Biospheres. Online September, 2014. The emeritus University of Copenhagen systems biologist continues his project to integrate many diverse approaches, theories, and aspects of this early occasion of proto-organic molecules, assemblies, cellular complexities, and so on into a succinct synthesis. He has schooled himself, as a long bibliography reflects, in contributions from Alexander Oparin in the 1930s to Sidney Fox and Freeman Dyson in the 1970s and 1980s to everyone today. Here the “colloid microsphere hypothesis” is revisited. A companion paper as humankind now learns altogether is The Origin and Spread of a Cooperative Replicase in a Prebiotic Chemical System by Julie Shay, Chris Huynh and Paul Higgs in the Journal of Theoretical Biology (Online September 2014).
Self-replicating molecules, in particular RNA, have long been assumed as key to origins of life on Earth. This notion, however, is not very secure since the reduction of life’s complexity to self-replication alone relies on thermodynamically untenable assumptions. Alternative, earlier hypotheses about peptide-dominated colloid self-assembly should be revived. Such macromolecular conglomerates presumably existed in a dynamic equilibrium between confluent growth in sessile films and microspheres detached in turbulent suspension. The first organic syntheses may have been driven by mineral-assisted photoactivation at terrestrial geothermal fields, allowing photo-dependent heterotrophic origins of life. Inherently endowed with rudimentary catalyst activities, mineral-associated organic microstructures can have evolved adaptively toward cooperative ‘protolife’ communities, in which ‘protoplasmic continuity’ was maintained throughout a graded series of ‘proto-biofilms’, ‘protoorganisms’ and ‘protocells’ toward modern life. Eventually, Darwinian speciation of cell-like lineages commenced after minimal gene sets had been bundled in transmissible genomes from multigenomic protoorganisms. (Abstract excerpts)
Egel, Richard, et al, eds. Origins of Life: The Primal Self-Organization. Heidelberg: Springer, 2011. With coeditors Dirk-Henner Lankenau and Armen Mulkidjanian, a large volume with these sections: Energetics of the First Life, Primeval Syntheses, Facets of an Ancestral Peptide World, and RNA Worlds – Ancestral and Contemporary. And might one wonder what kind of cosmos strives by way of us late collaborative creatures over a noosphere world, many billion years on, to reconstruct how life and mind came to be. Could such an apparent self-learning, observing, and selecting universal emergence be meant to engender the beginning of a second, intentional genesis?
If theoretical physicists can seriously entertain canonical “standard models” even for the big-bang generation of the entire universe, why cannot life scientists reach a consensus on how life has emerged and settled on this planet? Scientists are hindered by conceptual gaps between bottom-up inferences (from early Earth geological conditions) and top-down extrapolations (from modern life forms to common ancestral states). This book challenges several widely held assumptions and argues for alternative approaches instead. Primal syntheses (literally or figuratively speaking) are called for in at least five major areas. (1) The first RNA-like molecules may have been selected by solar light as being exceptionally photostable. (2) Photosynthetically active minerals and reduced phosphorus compounds could have efficiently coupled the persistent natural energy flows to the primordial metabolism. (3) Stochastic, uncoded peptides may have kick-started an ever-tightening co-evolution of proteins and nucleic acids. (4) The living fossils from the primeval RNA World thrive within modern cells. (5) From the inherently complex protocellular associations preceding the consolidation of integral genomes, eukaryotic cell organization may have evolved more naturally than simple prokaryote-like life forms. – If this book can motivate dedicated researchers to further explore the alternative mechanisms presented, it will have served its purpose well. (Publisher)