<P> The time periods between such devastating environmental events give time windows for the possible origin of life in the early environments . If the deep marine hydrothermal setting was the site for the origin of life, then abiogenesis could have happened as early as 4.0 to 4.2 Ga . If the site was at the surface of the Earth, abiogenesis could only have occurred between 3.7 and 4.0 Ga . </P> <P> In 2016, a set of 355 genes likely present in the Last Universal Common Ancestor (LUCA) of all organisms living on Earth was identified . A total of 6.1 million prokaryotic protein coding genes from various phylogenic trees were sequenced, identifying 355 protein clusters from amongst 286,514 protein clusters that were probably common to LUCA . The results "depict LUCA as anaerobic, CO-fixing, H - dependent with a Wood--Ljungdahl pathway, N - fixing and thermophilic . LUCA's biochemistry was replete with FeS clusters and radical reaction mechanisms . Its cofactors reveal dependence upon transition metals, flavins, S - adenosyl methionine, coenzyme A, ferredoxin, molybdopterin, corrins and selenium . Its genetic code required nucleoside modifications and S - adenosylmethionine - dependent methylations ." The results depict methanogenic clostridia as a basal clade in the 355 phylogenies examined, and suggest that LUCA inhabited an anaerobic hydrothermal vent setting in a geochemically active environment rich in H, CO and iron . M.D. Brazier has shown that the tiny fossils discovered came from a hot poisonous world of the toxic gases methane, ammonia, carbon dioxide and hydrogen sulphide . An analysis of the conventional threefold tree of life shows thermophilic and hyperthermophilic bacteria and archaea are closest to the root, suggesting that life may have evolved in a hot environment . </P> <P> Belief in spontaneous generation of certain forms of life from non-living matter goes back to Aristotle and ancient Greek philosophy and continued to have support in Western scholarship until the 19th century . This belief was paired with a belief in heterogenesis, i.e., that one form of life derived from a different form (e.g., bees from flowers). Classical notions of spontaneous generation held that certain complex, living organisms are generated by decaying organic substances . According to Aristotle, it was a readily observable truth that aphids arise from the dew that falls on plants, flies from putrid matter, mice from dirty hay, crocodiles from rotting logs at the bottom of bodies of water, and so on . In the 17th century, people began to question such assumptions . In 1646, Sir Thomas Browne published his Pseudodoxia Epidemica (subtitled Enquiries into Very many Received Tenets, and commonly Presumed Truths), which was an attack on false beliefs and "vulgar errors ." His contemporary, Alexander Ross, erroneously refuted him, stating: "To question this (Ed.: i.e., spontaneous generation), is to question Reason, Sense, and Experience: If he doubts of this, let him go to Ægypt, and there he will finde the fields swarming with mice begot of the mud of Nylus, to the great calamity of the Inhabitants ." </P> <P> In 1665, Robert Hooke published the first drawings of a microorganism . Hooke was followed in 1676 by Antonie van Leeuwenhoek, who drew and described microorganisms that are now thought to have been protozoa and bacteria . Many felt the existence of microorganisms was evidence in support of spontaneous generation, since microorganisms seemed too simplistic for sexual reproduction, and asexual reproduction through cell division had not yet been observed . Van Leeuwenhoek took issue with the ideas common at the time that fleas and lice could spontaneously result from putrefaction, and that frogs could likewise arise from slime . Using a broad range of experiments ranging from sealed and open meat incubation and the close study of insect reproduction he became, by the 1680s, convinced that spontaneous generation was incorrect . </P>

Who introduced the earliest belief that life was spontaneously generated from nonliving matter