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400 BCE
History of Animals
Aristotle publishes History of Animals. In which it discusses his theory on how some organisms are given birth to from a parent while others spontaneously appear in the right environmental situations. This is known to be the first real documentation showing the belief of spontaneous generation. -
Period: to
The belief that life is due to Spontaneous Generation
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Italian Discoveries
Italian scientist, Francesco Redi, is the first to disprove spontaneous generation by conducting an experiment that dealt with 3 jars of meat. One was sealed completely, one was covered with gauze, and the last was left out in the open. Through this experiment, Redi was able to prove that maggots hatched from eggs laid on the gauze and meat. -
Needham's Gravy Test
John Needham creates a rebuttal towards Redi’s results, challenging experiment.
Needham created a test in which mutton gravy was boiled so that all living organisms that could've been in it were supposedly killed. After this, the flasks containing gravy were sealed and a couple days later, microbes such as mould could be seen growing on the gravy. -
Spallanzani Disproves Needham
Spallanzani thought that Needham's experiment was untrue so he set off to recreate it. His experiment included one flask with a seal and one without. His results showed that the flask that was not sealed had no life while the other had signs of small organisms. This leads the scientific community to argue that the air that was in the other non-sealed flask lead to micro-organisms. -
Pasteur's Nail on Spontaneous Generation
Finally, to disprove the theory of Spontaneous Generation, John Pasteur developed an S-shaped neck for a container to stop microbes from entering the flask due to gravity. John Pasteur then boiled the broth and left it out for an entire year without any traces of life in it. He then broke off the neck of the bottle so that foreign organisms were able to enter the broth. After a few days, microbes began to form in the liquid. -
Watson-Crick DNA Model
After the rise of molecular biology, many considered the Watson-Crick DNA structural model as the origin of all life. This idea that life could come from chemical compounds and molecules certainly made more sense than the spontaneous combustion theory.
