Q.Who proposed that the first form of life could have come from pre-existing non-living organic molecules?

The Oparin-Haldane theory (also called the self-assembly or biochemical theory of the origin of life) proposes that life arose on Earth through the combination of simple chemicals reacting repeatedly over an enormous span of time. First suggested in outline by Haeckel, it was developed into a proper scientific theory independently by the Russian biochemist Alexander I. Oparin (1924) and the British biologist J. B. S. Haldane (1929). The theory describes a sequence of chemical stages: Earth's primitive, oxygen-free reducing atmosphere first formed as the planet cooled from a hot nebular cloud; its light elements (hydrogen, carbon, nitrogen, sulphur) reacted to form simple gases such as methane, ammonia, water vapour and hydrogen sulphide; under intense unfiltered ultraviolet radiation, lightning and volcanic energy, these gases underwent condensation, polymerisation, oxidation and reduction to form simple organic molecules (monosaccharides, amino acids, purines, pyrimidines, fatty acids, glycerol) that collected as Haldane's 'hot dilute soup'; further polymerisation built complex organic molecules (polysaccharides, fats, proteins, nucleotides), with the appearance of proteins/enzymes regarded as a landmark step; nucleotides then joined into self-replicating nucleic acids (RNA, DNA); nucleic acids combined with surrounding molecules to form protobionts — Oparin's coacervates (colloidal lipid-protein aggregates that grew and split) and Sidney Fox's microspheres/protenoids (more stable, membrane-bound hydrophilic aggregates) — which are thought to have developed into the first primitive living systems, or eobionts/protocells; and once a self-replicating RNA or DNA system developed within such a protocell, the first true cell (anaerobic and heterotrophic) had arisen.