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Aristotle
During Aristotle's time, many people were oblivious to the idea of spontaneous generation, but Aristotle was the first to document it in his book, The History of Animals. -
Microscopes
The development of microscopes led to people being able to see things never seen before. -
Francesco Redi
Francesco held an experiment in which he set out meat in open air and maggots only appeared on the meats which were not sealed because flies could drop in and lay eggs on the meat. This disproved the theory of spontaneous generation. -
John Needham
John Needham, an English clergyman, put together an experiment in which he boiled chicken broth and put it in a flask and then sealed it. Over time, microorganisms grew and he proved the theory of spontaneous generation. -
Lazzaro Spallanzani
Lazzaro Spallanzani performed the exact same experiment as Needham, but he sucked out the air inside the sealed flask. No microorganisms formed this time. He proved that spontaneous generation cannot occur without the presence of air and disproved Needham. -
Louis Pasteur
Louis, a French chemist, finally set the theory of spontaneous generation. He performed an experiment that was a variation of Spallanzani's and Needham's and just as he suspected no microorganisms formed in the experiment. At the same time, he refuted the theory of spontaneous generation and showed that microorganisms are everywhere. -
Alexander Ivanovich Oparin
Alexander, a Russian Scientist, published The Origins of Life. He described hypothetical conditions which he felt would have been necessary for life to first come into existence on early Earth and made some scientists acknowledge that some spontaneous generation might have taken place.
