2010-01-25 23:37:30
Since time immemorial, humans have observed that life appears seemingly out of nowhere, as if by magic. The ancient Egyptians watched as the Nile flooded their dry lands every year and frogs and fish emerged from the mud. For them the origin was clear: they emerged from the mud. In medieval Europe, grain was stored in silos and mice were quick to appear, according to popular belief, they hatched from wet grain. And it has always been seen that worms soon appear in fresh meat, that plants are filled with lice and aphids that, according to some, were born from dewdrops, etc. Life seemed to arise from inert matter, by spontaneous generation.
Aristotle made it very clear: “This happens in the pools, especially near Knidos, where on one occasion, they dried up and all the mud was removed. When the first rains came, the water began to fill them again and, immediately, small fish appeared (…) This evidence teaches us that certain fish are produced spontaneously and do not proceed from eggs or copulation. “.
This was the belief of Aristotle and, like him, a long cohort of scholars such as Saint Thomas Aquinas and Newton himself. Spontaneous generation was accepted as valid until 1668. That year, the Italian doctor Francesco Redi decided to check whether rotten meat worms really did arise spontaneously. He placed pieces of meat in different glass jars, covering some with a thin cloth and leaving others uncovered. The maggots only emerged in the meat of the uncovered jars, where the flies were able to lay their eggs.
The spontaneous generation of visible organisms was ruled out, but not that of microorganisms that escape with the naked eye. The microscope revealed a world of tiny creatures and made it clear that they had no problem populating, with all manner of microscopic bacteria and fungi, meat placed in sealed jars.
Another Italian, Lazzaro Spallanzani, dealt a new blow to spontaneous generation. He arranged several jars with pieces of bread inside, some jars he left open and others he boiled and closed to kill the organisms present. The latter were kept sterile. Thus, Spallanzani concluded, microscopic life does not generate spontaneously either. Even so, the defenders of spontaneous generation were still wrong. For them, boiling had not destroyed life but some inert product or “vital principle” that served as the basis for the appearance of life.
In 1860 the discussion between defenders and detractors of spontaneous generation had risen in tone to such an extent that the Paris Academy of Sciences offered a prize for experiments that managed to clarify the issue. The prize was claimed by Louis Pasteur.
Louis Pasteur decided to attack the problem once and for all. He began by designing a series of flasks with a very curious shape (some are still kept at the Pasteur Institute in Paris). Its spherical base and charged with liquid ended in a swan neck, that is, a very thin and elongated glass tube that curved allowing the passage of oxygen, necessary for life as it was thought, but prevented the passage of bacteria and other microorganisms. . Pasteur showed that if the liquid in the flask was boiled, leaving the neck intact, no microbes would appear, but if the neck was broken, microorganisms would pour in and contaminate the sample.
The sage presented his results during a scientific evening at the Sorbonne and, before the most select of the scientific community in Paris, declared: “The doctrine of spontaneous generation will never recover from the mortal blow dealt by this simple experiment.”
So strong was the blow that, for many years, no one dared to ask the most intriguing and difficult-to-answer question: If life begets life, how did the first living being come to be?
Listen to Pasteur’s biography.
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