Pioneers of Origin of Life Studies-Darwin, Oparin, Haldane, Miller, Oró-And the Oldest Known Records of Life.

The two basic approaches to elucidating how life began both date from Darwin. The first, that of the experimentalists, stems from Darwin's famous "warm little pond" letter to Joseph Hooker of 1871. This approach, an attempt to replicate the sequential events leading to life's origin, is exemplified by the "primordial soup" hypothesis of A.I. Oparin (1924) and J.B.S. Haldane (1929); the Miller-Urey laboratory synthesis of amino acids under possible primitive Earth conditions (1953); and Joan Oró's nonbiological synthesis of the nucleic acid adenine (1959). The second approach, that of the observationalists who search for relevant evidence in the geological record, dates from Darwin's 1859 , in which he laments the "" absence of a pre-Cambrian fossil record. Darwin's concern spurred a century of search that was ultimately rewarded by Stanley Tyler's 1953 discovery of diverse microscopic fossils in the ~1900 Ma Gunflint Chert of southern Canada. Tyler's find was soon followed by a cascade of discoveries worldwide; the establishment of a new field of science, Precambrian paleobiology; and, more recently, the discovery of 3400 and ~3465 Ma Paleoarchean microfossils, establishing that primordial life evolved early, far, and fast. Though progress has been made, much remains to be learned in the foci of this volume, for which this essay is the history-reviewing "stage setter".