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400 BCE
Aristotle and His Beliefs
During the era of Aristotle, people-- including scientists-- believed that simple living organisms could appear by spontaneous generation. The idea further bases on the belief that non-living objects could give rise to living organisms. It was a common knowledge that simple organisms could appear from a kind of environment. -
Recipes for Living Organisms
During the 17th century, there were man-made recipes for creating living organisms from inorganic matter. For example, Jan Baptista van Helmont had a recipe for mice. It was: 1)Place a dirty shirt or some rags in an open pot or barrel containing a few grains of wheat or some wheat bran.
2) In 21 days, mice will appear.
3) There will be adult males and females present, and they will be capable of mating and reproducing more mice. -
Francesco Redi's Experiment
Francesco Redi, an Italian scientist, opposed to the idea of spontaneous generation, and conducted an experiment with flies jars containing meat to test the idea that maggots were generated from rotting meat. He placed meat in three flasks, one open, one sealed and one with gauze. Maggots only appeared in the open flask, not in the sealed flask nor the flask covered by gauze. He believed this disproved spontaneous generation, however it has only proved maggots didn't come from meat. -
John Needham's Disproval
John Needham, a Scottish scientist, declared that microorganisms grew in soups that had been exposed to the air. He claimed "life force" was present in all inorganic matter, that could cause spontaneous generation to occur. To support his theory, he briefly boiled some of his soup and poured it into "clean" flasks with cork lids, which had microorganisms growing -
Lazzaro Spallanzani's Rebuttal
Lazzaro Spallanzani, an Italian biologist, made several variations of Needham's soup experiments. First, he boiled soup for an hour, then sealed the glass flasks by melting the mouths of the flasks. Soup in those flasks stayed sterile. Then, he boiled another batch of soup for few minutes before sealing the flask, and discovered that microorganisms had grew. In a third batch, he boiled soup for an hour, with flasks were sealed with corks. It had microorganisms grown. -
Needham and Spallanzani's Conflict
Spallanzani's experiment triggered arguments between Needham and Spallanzani over sterilization as a way of refuting spontaneous generation. Needham claimed that Spallanzani had boiled too much that he had killed the "life force." He claimed that bacteria could not develop in the sealed containers as the life force wasn't able to get in. Likewise, he stated that the boiling wasn't enough to destroy the life force that bacteria could develop. -
Solution by Paris Academy of Sciences
The debate of Spallanzani and Needham had become so heated that the Paris Academy of Sciences offered a prize for any experiments that would conclude the dispute. -
Louis Pasteur Claim for Prize
Louis Pasteur, a French scientist, recreated Needham and Spallanzani's experiment, leaving the bottles open to air. He designed a swan-neck bottle which gravity prevent access by airborne materials. He put covered the bottle then heated to kill microorganisms before observing any sort of growth. Although the broth could access air, there was still no life developing under the microscope. -
Alexander Ivanovich Oparin and "The Origins of Life"
Alexander Ivanovich Oparin, a Russian scientist, published a book called "The Origins of Life". He described hypothetical conditions which would be necessary for life to first come into existence on early Earth. Scientists concluded that under the very different circumstances of early Earth, some form of "spontaneous generation" might have taken place.
