The Origin of Life: Models and Data

Abstract

A general framework for conventional models of the origin of life (OOL) is the specification of a ‘privileged function.’ A privileged function is an extant biological function that is excised from its biological context, elevated in importance over other functions, and transported back in time to a primitive chemical or geological environment. In RNA or Clay Worlds, the privileged function is replication. In Metabolism-First Worlds, the privileged function is metabolism. In Thermal Vent Worlds, the privileged function is energy harvesting from chemical gradients. In Membrane Worlds, the privileged function is compartmentalization. In evaluating these models, we consider the contents and properties of the Universal Gene Set of life, which is the set of orthologous genes conserved throughout the tree of life and found in every living system. We also consider the components and properties of the Molecular Toolbox of Life, which contains twenty amino acids, eight nucleotides, glucose, polypeptide, polynucleotide, and several other components. OOL models based on privileged functions necessarily depend on “takeovers” to transition from previous genetic and catalytic systems to the extant DNA/RNA/protein system, requiring replacement of one Molecular Toolbox with another and of one Universal Gene Set with another. The observed robustness and contents of the Toolbox of Life and the Universal Gene Set over the last 3.7 billion years are thought to be post hoc phenomena. Once the takeover processes are acknowledged and are reasonably considered, the privileged function models are seen to be extremely complex with low predictive power. These models require indeterminacy and plasticity of biological and chemical processes.

The Future of Origin of Life Research: Bridging Decades-Old Divisions

“…This privileged position imposes a sequential, stepwise hierarchy on the OoL timeline: subsequent takeovers by the next world(s) until a living cell originates. Still, the question of which class of biomolecules initiated the OoL is a loaded question [61]. All known living cells contain DNA, RNA, proteins, lipids, coenzymes, and other metabolites-and the earliest cells as those known on Earth would have had to fulfil these minimal cell requirements [62].…”

The Origin(s) of Cell: Some Radical New Hypotheses

“…2. In order for simple bioorganic molecules to be assembled into more complex hetero-biomolecules, they also have to be stereochemically compatible with each other: in other words, there must be "molecular mutualism" (Lanier et al 2017;Vitas and Dobovišek 2018). Key examples of such "molecular mutualism" include that only some amino acids or peptides can bind with simple RNAs or that only some peptides can form α-helixes and then insert themselves into lipid membranes to make lipid membranes more permeable.…”

“…Three criteria should be applied to any new perspective regarding the origin of cell. First, it should provide a more coherent and consistent organization of existing data with fewer ad hoc hypotheses than existing ones, because it integrates new or previously underappreciated data (Lanier and Williams 2017). Second, it should resolve more controversies with fewer ad hoc hypotheses than existing ones (Pereto 2005;Fry 2011).…”

Closure of Earth’s Biosphere: Evolution and Current State

“…To propose a possible solution to this paradox, let us consider the history of the origin of the terrestrial biosphere. Very many published studies have been devoted to reconstructions of the history of Earth's biosphere based on existing geological and paleontological data (Lazcano, Miller, 1996;Russell et al, 2010;Lane et al, 2010;Dibrova et al, 2012;Sousa et al, 2013;Weiss et al, 2016;Lanier, Williams, 2017;Russell, Hall, 2006;Wächtershäuser, 2006;Kitadai, Maruyama, 2018;Amenabar, Boyd, 2019), and there is no sense in restating them here. One of the more interesting studies (Judson, 2017) In what follows, all factual material without references will be taken from the previously mentioned work (Judson, 2017).…”