Spontaneous generation, the hypothetical process by which living organisms develop from nonliving matter; also, the archaic theory that utilized this process to explain the origin of life. Many believed in spontaneous generation because it explained such occurrences as the appearance of maggots on decaying meat. Spontaneous generation is the hypothesis that some vital force contained in or given to organic matter can create living organisms from inanimate objects. Spontaneous generation was a widely held belief throughout the middle ages and into the latter half of the 19th century. Rejection of spontaneous generation is no longer controversial among biologists. By the middle of the 19th century, experiments of Louis Pasteur and others refuted the traditional theory of spontaneous generation and supported biogenesis.
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