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585 BCE
Anaximenes' Theory on Spontaneous Generation
The first records of the theory of spontaneous generation dates back to 585BC, when Anaximenes first thought that the life on Earth was formed by a a mixture of earth and water called "primordial terrestrial slime" that combined with the sun's heat to produce the living organisms on Earth. -
510 BCE
Anaxagoras Accepts "Terrestrial Slime"
20 Years after Anaximenes Death, Anaxagoras, another philosopher, took on the theory of spontaneous generation. He believed that when the Earth was created, seeds of plants were carried by the air and animals were formed in the aether. -
384 BCE
Aristotle's Take on Spontaneous Generation
Aristotle believed that some animals were created from their parent animals whilst other animal grew spontaneous and not from their parents. For example, he believed that insects were spontaneously generated inside the organs of dead animals. -
Francesco Redi's Experiment Disproves Theory
Redi did not believe that living organisms were created simply out of thin air so he designed a scientific experiment that disproves this theory. He placed two pieces of fresh meat into two different jars. One jar was left open, while the other jar was sealed with a piece of cloth. Several days later, he found out that the open jar contained maggots in the meat, whilst the sealed jar had maggots on top of the cloth, and not the meat. He concluded that it the maggots came from the eggs of flies. -
John Needham Proves Spontaneous Generation
John Needham, an English biologist, believed in the idea of spontaneous generation and set out to prove it. He designed an experiment involving water in a sealed broth and heating it and cooling it periodically. A few days later, he found life in the sealed bottle and thus concluded that life was created from non-living things. However, his conclusion was false since he failed to acknowledge that boiling water does not kill all organisms. -
Lazzaro Spallanzani Disproves John Needham's Experiment
20 years later after John Needham's experiment, Lazzaro Spallanzani tried to recreate the experiment. This time, however, all the air was removed from the flask prior to boiling. Since most organisms cannot survive without air, no organisms grew. -
Louis Pasteur's Swan Neck Experiment
Louis Pasteur designed an experiment that was very similar to John Needham's experiment. However, this time, after filling the flask with water and heating it to kill all life, he bent the neck of the flask to create a long tube in the shape of an "S". Doing this prevented organisms to enter the flask but also allowed air to flow. After a long time, no organisms grew in the water of the flask. When the neck of the flask was broken, organisms grew in the water rapidly. -
John Tyndall Concludes the Dispute
Tyndall proved that heat-proof organisms do exists and air and dust carried germs and bacteria. He also provided methods of fractional sterilization, which killed spores and stopped germination of bacteria.
