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350 BCE
The Theory of Spontaneous Generation Appears
The theory of Spontaneous Generation was first comprehensively proposed by Aristotle, an ancient Greek philosopher, in his book ”On the Generation of Animals”. This theory wanted to explain where life comes from and the seemingly sudden appearance of living organisms such as rats, scorpions or maggots. -
Redi’s experiment
Francesco Redi’s experiment was one of the first that started to disprove the theory of spontaneous generation. His experiment consisted of putting meat in three different jars. One without covering it with anything. Other with a stopper, and the last one covered with a cloth. The idea was to see if all three “produced” maggots. In the end it was proven that maggots don’t arise from rotten meat. -
Needham’s Experiment
Needham was a catholic priest and defender of spontaneous generation. In order to prove this theory he carried out an experiment that consisted of boiling a broth made with vegetable or animal matter, seeking to kill any existing microorganisms, and then sealing the flask. A few days later, he observed that one drop of the broth contained hundreds of microscopic lives. In his eyes, proving the theory of spontaneous generation. -
Spallanzani's Experiment
Disagreeing with Needham’s conclusions, Lazzaro Spallanzani carried out lots of experiments involving heated broth. He poured the broth into flasks, sealed them and heated them for long enough until there weren’t any microorganisms left. After some time the flasks still didn't have life in them but once Spallanzani opened them microbes rapidly grew in them. With that in mind Spallanzani concluded that spontaneous generation was false and microorganisms came from the contaminated air. -
Louis Pasteur's Experiment
Louis Pasteur also disagreed with the theory of spontaneous generation and carried to term an experiment in order to finally disprove it completely. He used 2 swan neck flasks and in each of them he put meat broth and boiled them to eliminate possible microorganisms. After a while he observed that none of them presented the presence of life since the air could get through the S shaped necks but the microbes couldn’t. With this he proved that organisms do not come from spontaneous generation.
