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350 BCE
Aristotle's " The History of animals"
The theory of spontaneous generation was first comprehensively posited by Aristotle in his book ”On the Generation of Animals” around 350 B.C., which aims to explain the seemingly sudden emergence of organisms such as rats, flies, and maggots within rotting meat and other decomposable items. The theory suggests that organisms do not descend from other organisms or from a parent, and only require that certain conditions in their environment be fulfilled in order for creation to occur. -
Invention of the microscope
Microscopy revealed a completely new world of microorganisms that appeared to arise spontaneously. Some scientists argued that while spontaneous generation might not apply to larger organisms like maggots and flies, it might still be applicable to smaller microbes. -
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Francesco Redi
Francesco Redi was aN Italian naturalist, physician, and poet, best known for his experiments in Florence, which were considered very important in refuting the theory of spontaneous generation, which postulated the production of living things from inert matter. -
Redi’s experiment
He made the first serious attack on the idea of spontaneous generation in 1668. At that time, it was widely held that maggots arose spontaneously in rotting meat. To achieve his goal of proving spontaneous generation to be wrong, he set out a controlled experiment. He also tests the spontaneous creation of maggots and flies by placing fresh meat in each of three different jars. thanks to this experiment, he was able to say that spontaneous generation on animals, was false. -
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John Needham
John Needhan was an English scientist and Catholic priest, defender of the theory of spontaneous generation. Needham carried out numerous experiments in which he prepared meat and vegetable broths. So, they were left in containers with cork stoppers that were not tight. In fact, he believed that boiling the broths, it would kill all the microorganisms in them -
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Lazzaro Spallanzani
Lazzaro Spallanzani was a biologist and a Catholic priest. He was appointed professor of physics and mathematics at the University of Reggio Emilia in 1757, and of logic, Greek and metaphysics, respectively, at Modena and of natural sciences at Pavia. -
Needham’s rebuttal
John Needham claimed that spontaneous generation could occur and performed what he considered the definitive experiment.
Needham briefly heated broth to its boiling point, to kill microorganisms, and poured it into flasks. Soon after the broth cooled, he sealed them. After some time, he observed living microorganisms in the sealed broth, thus concluding that spontaneous generation was a fact and contradicting Redi’s conclusions. -
Criticism from Spallanzani
Italian biologist and priest Lazzaro Spallanzani, set out to demonstrate that microbes do not spontaneously generate. Spallanzani poured the broth into flasks and sealed them. Next, he boiled the flasks for a long time, to kill present microorganisms. After some time, the broth did not have any trace of life. However, once he unsealed the flask, microorganisms rapidly grew in the broth. He concluded that spontaneous generation was false and microbes came from contaminated air. -
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Louis Pasteur
Louis Pasteur was a French microbiologist and chemist. He was known to the general public for his demonstration of the germ theory of a disease and his techniques for development and inoculation. -
Louis Pasteur experiment
Luis Pasteur designed several bottles with S-curved necks that were oriented downward. He placed a nutrient-enriched broth in one of the swan-neck bottles, boiled the broth inside the bottle, and observed no life in the jar for one year.Then broke off the top of the bottle or tilted the flask, exposing it more directly to the air and trapped particles, and noted life forms in the broth within days. He reasoned that the contamination came from life forms in the air, not a supposed “life force”.