Spontaneous generation is the belief that lower forms of life might spontaneously arise from non-living material. It stemmed from everyday (but incomplete) observations such as that insects and worms appeared from rotting meat, frogs from mud, and mice from rotting wheat. Spontaneous generation was proposed by Aristotle, espoused by theologians in the Middle Ages, including Thomas Aquinas, and upheld by the likes of William Harvey and Isaac Newton. Only when the hypothesis was properly put to the test by experiments, such as those of Redi (1668) Spallanzani (1765), de La Tour (1837), Schwann and, most decisively, by Pasteur (1862), was it seen to be in error. Any lingering doubts were removed by the work of Tyndall. However, the notion that life can develop from non-life, albeit over many millions of years, has been revived in the modern concept of the origin of life from prebiotic chemicals.
1. Farley, J. The Spontaneous Generation Controversy from Descartes to Oparin. Baltimore: The Johns Hopkins University Press (1977).