The biogenesis theory proposes the origin of life starting from pre-existing living beings. It opposes ancient ideas of spontaneous generation, where living organisms could be "born" from inanimate matter - including mud, decaying meat and even dirty clothes..
The first ideas related to biogenesis began to develop in the 17th century. The most important experiments that supported the theory of biogenesis were devised by Francesco Redi and Louis Pasteur.
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The main objective of biology is the study of life. For this reason, one of the most exciting - and intriguing - unknowns for biologists is proposing theories and formulating hypotheses to reveal how the origin of this phenomenon occurred..
There are endless theories that seek to solve this enigma. Below we will describe two of the theories about the origin of life that preceded the theory of biogenesis, to achieve a historical perspective on the subject.
Initially, life was thought to have been created by a divine creator. The forms created were perfect and immutable. This vision, based strictly on religious thought, began to cease to be convincing for the researchers of the time..
Later, the idea of spontaneous generation or abiogenesis was developed. This idea was retained by scientists since Greek times and was later modified until the 19th century..
It was common to think that life arose from non-living matter. Thus, this idea where life arises from inanimate matter was called "spontaneous generation".
Among the most striking postulates of the theory is the origin of animals such as snails, fish and amphibians from mud. Incredibly, it was thought that mice could originate from dirty clothes, after leaving them outdoors for about three weeks.
That is, the theory was not limited to the origin of life in ancient times. This also intended to explain the origin of current organic beings starting from inanimate substances.
According to the theory of biogenesis, life originated from other life forms that already existed.
This theory was supported by several scientists, among them Francisco Redi, Louis Pasteur, Huxley and Lazzaro Spallanzani; all these researchers stand out for their enormous contributions to biological sciences.
However, the theory of biogenesis assumes that all life appears alive. So we must ask ourselves, where did or how did that first form of life appear??
To achieve this weak - and circular - argument we must turn to theories of how life arose. This question was resolved by several researchers, including A.I Oparin and J.B.S Haldane. We will first discuss the experiments that succeeded in supporting biogenesis and then return to this question..
The experiments that supported spontaneous generation did not concern themselves with sterilizing the material used or keeping the container in which the experiment was carried out closed..
For this reason, flies or other animals (mice, for example) arrived and laid their eggs, which was erroneously interpreted as spontaneous generation of life. These researchers thought that they were witnesses to the generation of living organic beings from lifeless matter..
Among the most prominent experiments that managed to discredit abiogenesis are the contributions of Francesco Redi and Louis Pasteur.
Francesco Redi was a doctor from Italy who was curious about the spontaneous generation of life. To try to disprove this belief, Redi devised a series of controlled experiences to show that life could only appear from existing life.
The experimental design included a series of jars with pieces of meat inside and sealed with gauze. The role of the gauze was to allow air to enter, excluding any insects that could enter and lay their eggs.
Indeed, in the jars covered with gauze, no sign of animals was found and the eggs of the flies were trapped on the surface of the gauze. However, for the defenders of spontaneous generation this evidence was not enough to rule it out - until the arrival of Pasteur.
One of the most famous experiments was devised by Louis Pasteur in the mid-19th century, managing to completely eliminate the concept of spontaneous generation. These evidences managed to convince the researchers that all life comes from another pre-existing living being and supported the theory of biogenesis..
The ingenious experiment used bottles with swan necks. As we climb the neck of the flask in the shape of an "S", it becomes narrower and narrower..
In each of these flasks, Pasteur included equal amounts of nutrient broth. The content was heated to boiling to eliminate the microorganisms present there..
Over time, no organisms were reported in the flasks. Pasteur cut the tube in one of the flasks and quickly began a process of decomposition, becoming contaminated with microorganisms from the surrounding environment..
Thus, it could be proven with overwhelming evidence, thanks to Redi and finally to Pasteur, that life comes from life, a principle that is summarized in the famous Latin phrase: Omne vivum ex vivo ("All life proceeds from life").
Let's go back to our initial question. Today it is widely known that living organisms come only from other organisms - for example, you come from your mother and your pet, equally, was born from their respective mother.
But let's take the matter to the primitive environment where the beginning of life occurred. "Something" must have given rise to the first or the first living beings.
Currently, biologists support the hypothesis that life on earth developed from non-living substances that formed molecular aggregates. These aggregates managed to replicate adequately and developed a metabolism - remarkable characteristics of the beings that we consider "alive.".
However, we had already raised evidence that the living could not arise from non-living matter. So how do we solve this apparent paradox?
Earth's early atmosphere was very different from what it is now. The oxygen concentration was extremely low, there were lightning, volcanic activity, constant meteorite bombardment and the arrival of ultraviolet radiation was more intense..
Under these conditions, a chemical evolution could occur which, after a significant period of time, led to the first forms of life..
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