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400 BCE
Aristotle’s Theory of Spontaneous Generation
The first idea of spontaneous generation came from Aristotle, when he argued that the properties of all living organisms were due to the mixture of principles and elements of the earth. In The History of Animals, he provides the theory that some but not all living organisms are able to spontaneously generate out of matter. -
Francesco Redi's Experiment
Francesco Redi, an Italian scientist, designed an experiment to test the spontaneous generation in maggots, by placing fresh meat in two different jars, one was open, and the other was covered with a piece of cloth. The experiment only succeeded in the opened jar, therefore disproved the theory of spontaneous generation. -
Invention of the Microscope
During the 1700’s, the microscope was a key instrument and was widely used by scientists to observe microbes and prove their experiments regarding spontaneous generation. -
John Needham’s Challenge Theory
In 1745, Needham decided to challenge Redi’s previous theory by conducting an experiment where he heated broth in the bottle to kill any living organisms, then later reported the presence of life inside the broth. However, in actuality, Needham did no heat the broth long enough to kill all of the microbes inside. -
Lazarro Spallanzani’s Experiment
In 1768, Lazzaro Spallanzani, an Italian scientist, placed broth in two different bottles, boiled it to kill all living organisms inside, left one bottle opened, and the other closed. Several days later, the unsealed bottle had small living organisms inside, while the sealed bottle showed no sign of life. Spallanzani conducted a successful experiment and concluded that spontaneous generation is not a viable theory, however, he received several rebuttal claims for his experimentation. -
Louis Pasteur’s Experiment
Louis Pasteur, a French scientist, designed a curved neck bottle in 1859, and called it the swan-neck flask. Pasteur used heat to kill all the microbes in the broth, and left the end of the flask open to air. The S-shaped curved prevented dust particles and other microbes to reach the broth inside the flask. Life was not generated from the broth inside the flask, and therefore ended the tumultuous debate between scientists regarding spontaneous generation.
