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Aristotle (384-322 BC)
Aristotle was a Greek philosopher. In his book, The History of Animals, Aristotle states several times that some living beings and animals spontaneously form from the elements. His theory was that “vital heat” could form non-living matter, and that the surrounding elements determined the kind of organism. -
Jan 1, 610
Anaximander (610-546 BC)
Anaximander (611-547 BC) was a Milesian philosopher who believed that everything came out of nature and the elements. Anaximander claimed that living creatures were first formed in wet environments that were then developed in the sun. At the time there were other philosophers with similar views. -
Jan Baptist van Helmont (1580-1644)
Jan Baptist van Helmont was a Flemish chemist, physiologist and physician. He conducted many experiments to support the theory of spontaneous generation. In one experiment, he showed that while a willow tree grew in size and bulk, the soil the tree was gaining its mass from did not significantly decrease in matter. Therefore he believed that the mass of the tree was generated spontaneously. Helmont also wrote a ‘recipe’ for creating mice, which included old rags, wheat and a dark closet. -
Francesco Redi
Francesco Redi, an Italian physicist, came up with a hypothesis to prove the idea of spontaneous generation was false. Specifically, the theory that maggots could form from meat. He proved that maggots did not grow from meat, but rather were laid in eggs by adult flies. His experiment in 1668 found that meat that was covered, flies could not reach it, was free of maggots, while uncovered meat developed maggots. -
John Needham
In 1745, Needham rebutted and challenged Francesco Redi’s findings. He believed that heat was ‘lethal’ to all living organisms Needham theorised that if he took chicken broth and heated it, everything living in it would die. He heated the broth and let it cool and sit in a constant temperature. A thick, cloudy, solution of microorganisms developed in the broth. This was was, in Needham’s mind, strong evidence of spontaneous generation -
Lazzaro Spallanzani (1729-1799)
Spallazani pepeated the experiments of Needham. But he removed air from the flask as he suspected air contaminated the broth and boiling the broth did not kill everything. His experiment was as follows: He put broth in two separate flasks and boiled the broth in both flask. Then he sealed one flask and left the other open. Days later, the unsealed flask had small living things that he could observe more clearly with the newly invented microscope. The sealed flask showed no signs of life. Althoug -
Charles Cagniard de la Tour and Theodor Schwann
Cagniard and Schwann published their discovery of yeast in alcohol fermentation in 1837. They discovered that when only sterile air or pure oxygen was introduced into the substance and the presence of yeast was denied, fermentation would never happen. This suggested that airborne microorganisms, not spontaneous generation, caused the fermentation. This discovery is important as it solidified Louis Pasteur’s experiment some 20 years later -
Louis Pasteur
Pasteur was a notable French scientist. He wanted to recreate Needham and Spallanzani’s experiment, but leave the flask open to air. Pasteur designed ‘swan neck’ flasks; bottles with ’S’ shaped necks so that gravity prevented airborne foreign materials to get in. He placed nutrient enriched broth in the flask and boiled the broth. He observed the broth for one year and saw no life. When he broke off the top of the bottle – exposing it to air – he saw life forms in a matter of days. As long as t -
John Tyndall
Tyndall’s experiments showed the existence of heat-resistant spores in many materials. These spores could not be killed by boiling, which included spores in chicken broth and other things. His discovery xxplains the results of Needham’s experiments.
