The colloidal model of life’s emergence provides fresh insights into what life is and how first life came about.<br/>At the molecular level, non-covalent forces ensure the colloidal stability of growing and dividing cells, crowded with closely interacting biomacromolecules. The key forces are hydrogen bonding (including hydration and the hydrophobic effect), screened electrostatic forces, and “hard-core” repulsions; their commensuration and temperature independence clarifies the physicochemical conditions necessary to create the living state of matter. These non-covalent forces, together with biochemical reactions, control the spatiotemporal sequences of cytoplasmic, sol-gel transitions during the cell cycle—the metabolic and genetic processes of being alive. Theory predicts that gelled (concentrated) biomacromolecules are separated by ion-conducting channels regulated by biochemical “tagging” reactions, such as phosphorylations and methylations (and many others). To be alive, the Last Universal Common Ancestors (LUCAs) already had a similar level of colloidal sophistication about 3.5 billion years ago.<br/>At the macroscopic, chemical engineering level, the rotating Earth is a reactor, where multicomponent and multiphase chemistry took place in the atmosphere, hydrosphere, and lithosphere. When proto-organic molecules composed of CHNOSP atoms accumulated in intertidal zones, their variety was simplified by cyclic phase separations (self-purifications) in colloidal sediments rich in potassium and magnesium ions (cf. the Usiglio sequence of marine evaporites). These ions participated in the coevolution of proteins and RNAs, which in turn became dependent on them. Thus, the "RNA World" originated in briny, colloidal occlusions within sediments patterned by cycles of hydration and dehydration. The first cell cycles of prokaryotic-like organisms emerged “on the fly” from such sedimentary occlusions; they were energized by tidal, wet-and-dry cycles and solar, day-and-night irradiations, the natural agents of life’s creation.<br/>These colloidal processes of biochemistry and geochemistry can be arranged as a jigsaw puzzle of eight evolutionary stages, including the evolutionary stage of biomacromolecular crowding that directed Earth’s chemical evolution toward the living states of matter. The puzzle suggests a number of experiments with multicomponent and multiphase compositions using cyclically driven chemical processes.

Origin of life as a problem in colloidal biochemistry and geochemistry

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