-
300
Aristotle Spreads the Idea of Spontaneous Generation
Aristotle was the first to believe, and spread, the idea of sponaneous generations: the theory that living organisms generated from non-living things, or from living organisms that have little genetic similarites. Aristotle belived that the amount and variety of an organisms 'vital heat' generated different organisms. -
Francesco Redi Challenges Aristotle's Theory
Francesco Redi belived that living organisms couldn't possibly 'spontaneously generate'. In order to disprove Aristotle's long standing theory, Redi conducted an experiment in which he placed a piece of meat in two jars. He covered one with a cloth, but left the other one uncovered. After waiting a while, Redi found that the uncovered meat was teeming with maggots, while the covered meat was devoid of any living organisms. Redi thought that this disproved the idea of spontaneous generation -
John Needham Tries to Prove Redi Wrong
John Needham didn't belive that Redi's experiment was conclusive enought to disprove Aristotle's theory. He conducted his own experiment by boiling meat broth until all living organisms were killed, then put half in one jar and half in another. He covered one and left the other uncovered, like Redi, and waited. When he looked back at the jars, he found that both were cloudy and filled with living organisms. This proof concluded that Aristotle's 'spontaneous generation' theory was true. -
Lazzaro Spallanzani Investigates Redi's and Needham's Experiments Part I
Lazzaro Spallanzani critically examined both Redi's and Needham's experiments and concluded that Redi was correct and that Needham's experiment was flawed. He suggested that Needham didn't let the broth boil for long enough to kill everything living in it. Spallanzani re-did Needham's experiment, this time making sure that the broth was boled enough. Spallanzani found that the covered jar was clean of life. -
Lazzaro Spallanzani Investigates Redi's and Needham's Experiments Part II
However, many people didn't believe Spallanzani because they thought that the air was necessary for 'sponaneous generation'. Spallanzani's theory was widely disliked. -
Louis Pasteur Disproves 'Spontaneous Generation' Once and for All
Pasteur decided to disprove Aristotle's theory, by creating a flask that let air flow in, but blocked any organisms from touching the contents of the flask. Pasteur called this a swan-necked flask. He conducted an experiment similar to Needham's, except he used an open flask and a swan-necked flask, instead of covered/uncovered. He found the swan-necked flask free of life, while the open flask was not. This finally disproved the theory of 'spontaneous generation' because there was air flow.
