ABSTRACT
First cells in vivo (the last universal common ancestors, or LUCAs) were as complex as extant prokaryotic cells: multiphase, multicomponent, molecularly crowded, in cyclic disequilibrium, and re-emergent—with biochemistries comparable to those of today’s prokaryotes. The evolution of complexity can be framed as a jigsaw puzzle of chemical reactions, colloidal phase separations and geochemical consolidations, driven by planetary cycles of diurnal temperatures and tidal (seawater) hydrations-dehydrations. The physicochemical nature of the jigsaw puzzles affords new insights into the problem of life’s emergence: Schrödinger’s putative physical laws of life are unnecessary; cycling phase separations bring about evolutionary chemical purifications of Earth’s complex (“tarry”) prebiotic chemistry toward simpler biochemistry of all life; abiotic/biotic transitions arise when non-covalent molecular forces (biomacromolecular crowding, hydration, and screened electrostatic forces) become commensurate at about one nanometer, allowing the evolution of molecular recognition (genetics, metabolism, and cellular self-organization); cyclic fusions of cells and of cells with environmental nucleic acids generate evolutionary saltations (natural genetic engineering); and the physicochemical jigsaw puzzle explains biological terms such as becoming alive, being alive (or dead), and being alive and evolving. Specific but challenging experiments in the chemical bottom-up and microbiological top-down paradigms are suggested; they are based on “self-purifying” complex chemical mixtures that evolve under cyclic (PCR-like) processes.
