originoflife

The origin of life refers to the natural processes by which living systems emerged from non-living matter on Earth. It encompasses the initial appearance of self-replicating molecules, basic metabolic processes, and the first cellular forms. The field, often called abiogenesis, seeks to understand how chemical complexity translated into biology, and what conditions and steps made such a transition possible. Evidence places the emergence of life at least 3.5 to 3.8 billion years ago, with the oldest well-preserved cellular remains from that era.

A traditional framework emphasizes prebiotic chemistry in the early Earth environment. In models such as the primordial soup, simple organic molecules formed from inorganic precursors under energy sources like lightning or UV radiation, gradually assembling into more complex biochemicals. The famous Miller–Urey experiments in the 1950s demonstrated that amino acids and other organics could arise from plausible early-Earth conditions, supporting the idea that life's building blocks can emerge spontaneously under suitable chemistry.

Several complementary hypotheses address how these molecules became a living system. The RNA world proposes that RNA molecules acted as both information carriers and catalysts before DNA and proteins, enabling self-replication and evolution. Metabolism-first ideas emphasize autocatalytic chemical networks and the development of compartmentalized, metabolism-enabled protocells. The lipid world concept highlights the role of lipid membranes in forming primitive, selectively permeable compartments that could harbor chemical reactions.

Other propositions include hydrothermal-vent environments providing chemical energy and minerals to sustain early life, and panspermia, which considers the delivery of life's precursors or life itself from space. Ongoing research combines chemistry, geology, microbiology, and planetary science to illuminate plausible pathways from chemistry to biology.