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5000 BCE
aristotle and spontaneous generation
Aristotle proposed that life arose from nonliving material if the material contained pneuma -
Period: 5000 BCE to 5000 BCE
aristotle and spontaneous generation
Aristotle proposed that life arose from nonliving material if the material contained pneuma -
redi's photo experiment
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Redi’s experiment
To achieve his goal of proving spontaneous generation to be wrong, he set out a controlled experiment. Redi went on to demonstrate that dead maggots or flies would not generate new flies when placed on rotting meat in a sealed jar, whereas live maggots or flies would. -
Needham’s photo experiment
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Needham’s rebuttal
The hypotheses of spontaneous generation continued. In 1745, John Needham, proposed an experiment that he considered the definitive.
Boiling killed microorganisms, so he proposed to test whether or not microorganisms appeared spontaneously after boiling broth.
He boiled chicken broth, put it into a flask and waited until microorganisms grew. Finally, he observed living microorganisms in the broth, concluding spontaneous generation was a fact. -
Criticism from Spallanzani
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Criticism from Spallanzani
He did not agree with Needham’s conclusions, so he performed hundreds of carefully executed experiments using heated broth.
First, he sealed flasks with chicken broth inside. Then, he boiled them for a long time. Later, he observe that the broth did not have any trace of life, but when he unsealed the flask, microorganisms fastly appear in the broth.
He concluded that spontaneous generation was false and microbes came from contaminated air. -
Spontaneous generation to rest photo experiment
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Pasteur puts spontaneous generation to rest
Louis Pasteur re-created the experiment and left the system open to air. He boiled meat broth in a flask, heated the neck of the flask in a flame until it became pliable, and bent it into the shape of an S.
Air could enter the flask, but airborne microorganisms could not. Any microorganisms grew, as Pasteur has expected but when he tilted the flask, the broth rapidly became cloudy with life. He concluded that the contamination came from life forms in the air, not a supposed “life force” -
final remarks
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Final remarks
IIn 1864, Pasteur articulated “Omne vivum ex vivo” (“Life only comes from life”).In this lecture,
is recounted the famous swan-neck flask experiment stating. Pasteur and others used the term biogenesis as the opposite of spontaneous generation.