The spontaneous generation it is one of the first theories that was raised to explain the origin of life. Specifically, it proposed that living beings could arise spontaneously, without the need for other “parental” organisms, from non-living or inanimate matter..
Although in modern times it seems to be quite obvious, ideas about the spontaneous generation of different organisms considered "vermin", and phenomena such as fermentation and putrefaction, governed philosophical and scientific discussions for many years..
This conception of nature lasted for many centuries, but it is not considered as true in our days, since different characters dedicated themselves to successfully deny it..
Different philosophers and scientists throughout the history of humanity have given themselves the task of asking themselves where we come from and where all the other forms of life that accompany us on the biosphere came from.
Ideas about spontaneous generation date back to the Old Age. Both classical Greek philosophers and many other thinkers who lived until the mid-19th century fervently accepted that living organisms originated spontaneously from inert materials, with no other parental organisms..
Thus, for many centuries the idea was held that insects, worms, rats and other vermin formed spontaneously in mud or in any accumulation of decomposing matter..
Some texts maintain that Aristotle, the great Greek thinker, was one of the first to sketch the foundations for what would later become the theory of spontaneous generation, since he claimed that life could arise from matter don't live, as long as it had what he called vital heat.
Through observation, Aristotle concluded that some life forms originated from different materials. The testes - a genus that included snails and bivalves - were generated from mud; clams rose from the sand, oysters from silt and barnacle from hollows in the rocks.
Aristotle thought that every living being arose from the combination of two principles: the active and the passive. For example, from the dead meat of animals (active principle), flies were born by the action of air and heat (passive principle).
In short, the theory of spontaneous generation proposed that life arose from inanimate or decomposing matter, and not necessarily from another living being parental.
Some thinkers were in favor of the fact that living organisms could form spontaneously from inorganic matter, while others considered that an organic base was necessary for this purpose..
In addition to the ideas of Aristotle in ancient times, there are two later scientists who supported the theory of spontaneous generation based on the results of their experiments:
Van Helmont proposed that mice could be generated spontaneously in ragged tissues and on wheat grains left in open containers for 3 weeks..
However, in reality it was that these tissues comprised favorable environments for the protection, feeding and proliferation / reproduction of these animals. That is, the mice came to live at the place of his experiments when he placed the tissues and wheat.
As a supporter of ideas about spontaneous generation, Needham's claims were based on an experiment that consisted of briefly boiling a broth made from plant or animal matter, seeking to kill any pre-existing microbes, and then sealing the container that contained it..
A few days later he found that the broth was cloudy and observed that a single drop of it contained hundreds of microscopic life forms (single-celled organisms)..
Since he considered that the conditions under which he had carried out this experiment were adequate, he concluded that these microbes must have arisen spontaneously. However, the mistake was that it did not actually boil the broth enough to kill all the microorganisms present there..
Francesco Redi, in 1668, was the first scientist who experimented to be able to reject spontaneous generation.
In his first experiment, he placed pieces of meat in three identical glass containers, two sealed and one open. A few days later, the discovered meat showed the presence of worms, while the others, despite being decomposed, did not present worms..
Critics of his experiment said the problem was that no air was allowed to enter the jars. So Redi decided to do a new experiment with an open bottle, another with cloth to let the air pass, and another sealed with cork. The result was that the flies laid eggs on the cloth, outside the jar, but were unable to enter. In the open jar they went in and laid eggs, and in the sealed no.
With his experiments, Redi showed that no larvae could form on decayed meat if the presence of any adult insects that could lay their eggs were prevented, thus laying the groundwork for other detractors of these theories..
Lazzaro Spallanzani dedicated himself to the study of different microscopic life forms and showed that when a nutritious sauce was boiled and packed in airtight containers, no living thing grew.
After boiling a culture broth, he placed it at rest in open and other closed containers. In the closed containers there were no presence of new organisms, while in the open ones living organisms were generated.
Later, in 1861, the well-known French bacteriologist Louis Pasteur devised a series of brilliant experiments that showed that there could be no such thing as spontaneous generation. These experiments were based on the following statements:
Based on these premises, Pasteur designed an experiment to test whether microbial life could spontaneously be created in a sterile nutrient broth.
He initially took two containers and added nutrient broth into each one, then folded the neck of each container, shaped it into an “S” shape, and proceeded to boil them to kill any microbes inside. He cut the neck in "S" of one of the containers and left the other intact, letting them rest for a while..
In the container with the broken neck, the rapid growth of microbes was appreciated, while in the one that remained intact the microorganisms could not reach the broth, accumulating in the "belly" of the neck. With this he concluded that without the introduction of powder in the sterilized culture medium, no life could grow..
For many scientists of the time, Pasteur's experiments not only demonstrated the impossibility of spontaneous generation, but also suggested that it was useless to continue trying to elucidate the origin of life, since they considered that life had no origin, but was eternal as well as matter.
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