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350 BCE
Aristotle on Spontaneous Generation
Aristotle writes the book History of Animals approximately in 350 BC, a book regarding the many biological wonders of the world. He briefly touches on the subject of spontaneous generation in his book. He talks of spontaneous generation as the origin of some species, and that these species generate from previously living organisms, such as rotting flesh or vegetable matter. He explains one of the examples as insects, which he claims spontaneously generates from animal’s organs. -
Francesco Redi - The Glass Jar Experiments
It was a common belief that maggots generated from rotting meat, a clear example of spontaneous generation. To disprove this, Redi set out glass jars with meat. Half of them were left open, and the half were covered with a fine muslin cloth. Maggots swarmed over the open jars, but the jars with the muslin cloth were covered with flies were landing on the cloth to lay eggs, which then hatched into maggots. From this, Francesco Redi disproved that maggots spontaneously generate. -
Needham/Spallanzani Controversy - John Turberville Needham Findings
A series of experiments conducted by the Irish priest John Turberville Needham was published. These results were widely believed to prove the spontaneous generation theory. Needham’s first experiments found that when mutton gravy was distilled in a sealed glass tube, the fluid afterwards was full of microorganisms. -
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Needham/Spallanzani Controversy
In response to the disproval of his experiments, Needham further challenged Spallanzani, claiming that boiling the liquid too long would deprive the closed system of oxygen, thus preventing the organisms to flourish. Later experiments showed that the tube would indeed be deprived of oxygen. The experimental outcome was undetermined, so the controversy continued throughout the 1780s. -
Needham/Spallanzani Controversy - Lazzaro Spallanzani's Findings
Lazzaro Spallanzani, an Italian cleric, carried out experiments challenging these claims and first published his results in 1765. He claimed that he didn’t see any “organic molecules” and that when he repeated this experiment of putting distilled liquid in a sealed glass tube without yielding any of the same observations and results. -
The Charles Darwin Controversy
In the first edition of his book: On the Origin of Species, Darwin carefully avoids the subject of spontaneous generation until the end, where he briefly touches on it: “Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed.”
— Darwin, On the Origin of Species This line caused outrage in the science community, but he still chose to be ambivient. -
Louis Pasteur and the famous 'Swan-Necked Flask' experiment
The swan-necked flask was a flask with a long and thin tube that curved very similarly to a swan-neck. The opening allows gas to pass through but prevents the other elements of the air entering. He emulated Needham's experiment, leaving distilled liquid in the flask. Nothing grew in the liquid, disproving both Needham's experiment and the spontaneous generation theory. If microbes didn't grow on the liquid, then the microbes must originate from dust in the air rather than spontaneous generation. -
Louis Pasteur Preceding the 'Swan-Necked Flask'
Preceding the famous ‘swan-necked flask’ experiment, he carried out a lengthy series of experiments. One of which included an observation in which it was perceived that he believed that the air held microbes, thus leading him to the swan-neck experiment. Air was led through dense gun cotton filters, which were then dissolved. The solid particles trapped from the air were examined microscopically, and Louis Pasteur observed spherical bodies that he assumed were the ‘germs’ of microbes. -
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Charles Darwin Theory of Evolution Controversy Part 1
After Charles Darwin released the theory of evolution to the public, many medical professionals delved into the topic of spontaneous generation, some of which still seeking to prove that it is still a plausible theory. It was thought by some that Darwin’s theory of evolution required spontaneous generation to explain in a non-miraculous way where the origin of all species originated from. -
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Charles Darwin Theory of Evolution Controversy Part 2
John Tyndall, a physicist was certainly not one of these people. He gave a famous lecture in January 1970 on “Dust and Disease”, arguing that doctors must accept the germ theory, a theory that states that bacteria and germs do not spontaneously generate in the human body, but rather they enter the human body through other means such as infection or respiratory means due to the evidence that suggests bacteria and germs travel through dust in the air. -
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Charles Darwin Theory of Evolution Controversy Part 3
Henry Charlton Bastian was one of the leading scientists that opposed John Tyndall and followed the idea that spontaneous generation had to exist in some way in order for Darwin’s theory of evolution to make sense. He conducted experiments using a device that was vacuumed of all dust particles in order to prove spontaneous generation was possible. -
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Charles Darwin Theory of Evolution Controversy
Darwin received news of this, and people believed that Bastian’s evidence could help support Darwin’s theory of evolution because his theory was missing the explanation of how the origin of all species came to be. Charles continued to be ambivalent, only agreeing that the origin of life emerged from nonlife by a natural process in the beginning. He believed that after the origin of life came into being, every single other species in existence evolved from this single organism. -
Watson–Crick DNA Model
Soon after the rise of molecular biology, many considered the Watson-Crick DNA structural model as the origin of all life. The idea that life could come from chemical compounds and molecules certainly made more sense than the spontaneous combustion theory. -
Urey–Miller Experiment - Amino Acids
The Urey–Miller experiment provided further evidence that the origin of life could come from chemical elements (from Amino Acids rather than DNA). In their experiment, an electrical discharge passed through a mixture of steam, hydrogen, methane, and ammonia in a sealed container produced amino acids. This provided evidence that the origins of life likely came from the Amino Acids.
This discovery eventually removed the use of spontaneous generation to prove Darwin's evolutionary theory.
