In order to understand how life emerges, from the tiny unicellular beings to the complex multicellular organisms in which we have evolved, a multitude of hypotheses have tried to offer a sufficiently valid and contrasted explanation. At the time, the defenders of the spontaneous generation theory were convinced that they believed they had found the answer, and for centuries it seemed that they were right.
If you want to understand the explanations that used to be given about phenomena that today are well known and whose origin is known for sure, it is necessary to make an exercise of change of perspective, something that is not easy at all.
This means we need to go back in time, to a period in which science was still wearing "a nappy," and when it was not well seen by a social majority that blamed everything on the divine's will and opposed contrastable evidence threatening to overthrow their beliefs.
However, even many philosophers and scientists from the past that are considered key in our advance as a society, were in favor of the spontaneous generation theory.
In other words, spontaneous generation held that life could originate from inanimate matter.
The first ones to talk about the ability of life to emerge from the most unsuspected places, were ancient Greek philosophers, such as Anaximander or Thales of Miletus.
These thinkers considered that from the interrelationship of, for instance, heat from the rays of the sun, the action of air or the humification left by rain, with the accumulation of garbage, wet mud or rotting food, new life could be created.
So, this first version of the spontaneous generation theory allowed to explain the origin of creatures such as insects, worms or small vertebrates (lizards or frogs).
With Aristotle, who was subsequent to the ones mentioned, the materialistic paradigm changed to one of a different nature. According to him, a divine impulse, called "entelechy", manifested itself through energy and breathed life into lifeless matter.
Contrary to the ideas of Ancient Greece, a more skeptical and directed towards the scientific method current emerged (although erroneous in its development), that said that life cannot be created from something that has never been alive, but it can arise from, for example, a decomposing body.
As mentioned, to some extent this approach is correct, but it stumbles when trying to explain the reason.
As we mentioned at the beginning of this article, it was not only the general population who was in favor of this belief, but there were some reputed sages also supported it.
So far, the Aristotelian doctrine was the only explanation for the phenomena that happened in nature: everything came from an energy that was given to inert substances.
However, Bacon believed that this thought clashed head-on with science, so his job was to try and prove that the Greek philosopher was mistaken and that it had to be exiled as a source of real knowledge.
Although he denied that the "entelechy" existed, Bacon supported the spontaneous generation theory, because, for him, the causes of it lied in the combination of some factors that made it possible for life to flow and that it was possible to analyze and explain by parts using the inductive method.
One of the greatest exponents of rationalism, René Descartes, believed fervently in the spontaneous generation theory, but by divine intervention. Probably, his years of education in a Jesuit center influenced Descartes in developing his postulates, which gave an important role to God.
Thus, for the French mathematician, God, the infinite and perfect substance, was the one who created all substances, thinking (the soul or the mind) and physical (the material world).
Also, the father of classical physics was throughout his life a dedicated man of faith, convinced that God is the only one who brought life to Earth, reminiscences from his passion for Ancient Egipt.
In spite of being branded as a non-believer due to his antitrinitarian faith, Newton was convinced that the work of God was the only thing that could explain the building of the pyramids and the rest of the architecture of this civilization, thought that he generalized to every phenomenon that occurred in nature.
The English biologist postulated, like Aristotle, that a vital impulse originated genuinely in the inanimate matter was the cause of life.
To sustain his hypothesis, he carried out an experiment that consisted on boiling meat and letting it rest in a badly closed container on purpose. For Needham, the agent who infused life was air, so that if a certain amount of time went by and organisms that were not previously present appeared in the mixture, the theory of spontaneous generation would be proven. When he confirmed his hypothesis, he thought that this experience was enough to validate it.