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Aristotle's Theory of Spontaneous Generation
Aristotle (around 330 B.C.) was the one who first coherently synthicized the theory of spontaneous generation by compiling and expanding the work of previous philosophers. Aristotle's theory held sway for two millenia. -
Jan Baptist van Helmont (1580–1644)
Jan Baptist van Helmont was on of those who was thought to have proved the theory fo spontaneous generation. He did this by noting that as a willow tree gets larger, the soil it is planted in decreases in mass. He also included in his notes recipies to 'generate' mice from meat and scorpions from basil placed between two bricks. -
William Harvey (1578 – 1657)
William Harvey disproved Aristotle's theory that eggs come from a coagulation in the uterus by dissecting a deer, showing that there was no visible embryo during the first month of pregnancy. He concluded that life came from invisible eggs. Remember, this was before microscopes. -
Fransesco Redi (1626-1697)
Fransesco Redi worked to prove or disprove the theory of spontaneous generation, using some of the same theories that the later Louis Pasteur used. -
Invention of accurate compound microscopes
Christiaan Huygens (1629-1695) invented a simple 2-lens ocular system in the late 17th century that was achromatically corrected, which was a huge step forward in microscope developement. It was in the 17th century that microscopes became well-known to biologists, mainly through the work of Antonie van Leeuwenhoek (1632-1723), who made simple microscopes with small but very powerful lenses. -
Pier Antonio Michelli (1679-1737)
Observed that when fungus spores were placed on a slice of melon, fungus of that type of spore arose on the melon. By this he concluded that fungus does no arise from spontaneous generation. -
John Needham (1713-1781)
Beleiving that boiling killed all living things, he conducted a serious of experiments using boiled broths and showed that, when sealed right, the broths would cloud. This allowed the belief in spontaneous generation to persist. -
Lazzaro Spallanzani (1729-1799)
Lazzaro Spallanzani attempted to avoid exposing a mixture to the air between boiling and sealing, as this created a variable. He did this by boiling broth in a sealed container with partial evactuation, and he witnssed no life growth, but his works were not taken as proving or disproving spontaneous generation, as it became assumed that air was required to create life from non-life. -
Charles Cagiard de la Tour and Theodor Shwann
They both published their independant theory on yeast in alcoholic fermentation. They reached their conclusions by observing yeast cells devide in the foam of left over brewed beer, and by discovering, by exoerimentation, that the cells would not devide if given stale air or pure oxygen. This implied that air particles in the aire were the cause. -
Louis Pasteur (1822-1895)
The work of louis Pasteur finally disproved the theory fo spontaneous generation in 1859. He did this through designing several s-shaped bottles pointed downwards, so gravity prevented dust and other such things from entering the bottle, filled the bottle with some nutrient-rich broth and boiled it in the bottle, then left it, observing no life for one year. This officially proved that life could not be created from nonlife even if air was present.
