Biogenesis theory: explaining the appearance of life

Life itself hides many secrets that escape human comprehension. One of the greatest mysteries is the origin of all life, an idea that has haunted the thoughts of humanity and that has always been tempting our curiosity. For this reason, there have been several attempts to explain this stage, either through faith or science.

Numerous theories have arisen throughout history to try to explain the origin of life, such as the theory of biogenesis. This model indicates that life can only be generated from a pre-existing life. Very simple to understand: a hen is born from the egg laid by another hen. It is not an explanation with much more mystery, but its importance lies in the fact that it focused on the theme of the origin of life, since at the time of its appearance the idea of ​​the generation spontaneous.

• You may be interested: "The theory of biological evolution"

At the beginning: the theory of spontaneous generation

The truth is that one cannot talk about biogenesis without first mentioning the model that displaced the scientific and popular scene. Spontaneous generation proposed that

life can be generated from inert matter. This idea came from the observation that after the putrefaction of an organic sample insects and microorganisms appear that were not there before.

It was quite an achievement that the theory of biogenesis managed to disprove a model that had been rooted in the conception of the world for many years. The idea of ​​spontaneous generation dates back to ancient Greece, from the hand of Aristotle; the philosopher maintained that some forms of life could appear without more from inert matter. For example, worms came out of sun-warmed mud, or flies from rotting meat.

These convictions that Aristotle proposed survived for many centuries without anyone questioning them. It was not until the seventeenth century when someone wanted to deny the idea. It was the Italian naturalist Francesco Redi.

Redi's experiment

This researcher devised an experiment to show that insects do not generate spontaneously. For this, he put in eight glass jars different types of meats, leaving four of them completely uncovered, while the other half covered them with gauze, which allowed air to pass but not insects

After a few days, the uncovered meats presented larvae, while the covered ones apparently did not harbor, apparently, life. The result of the experiment showed that it is necessary for the flies to lay their eggs in the meat so that others of their species appear. It is an experiment that is linked to the theory of biogenesis and that would have been a success to unseat the spontaneous generation were it not for the discoveries of the Dutchman Anton Van Leeuwenhoek, the father of the microbiology.

Leeuwenhoek, a few years after the Italian conducted his research, repeated Redi's experiment, but this time he examined the meats under a microscope. Microorganisms could be observed in both uncovered and covered meats, a result that kept the ideas of spontaneous generation feasible at least for these living organisms.

Pasteur's experiment

The theory of spontaneous generation lasted a couple of centuries more, despite the fact that there were earlier attempts to disprove it, such as those made by the priest Lazzaro Spallanzani, who showed that if you carefully close a container with broth and heat it, microorganisms will not grow; but the supporters of the orthodoxy of the moment attributed this to the fact that he had killed all life by heating it.

It was not until 1861, when French chemist Louis Pasteur he unequivocally demonstrated that these beliefs were false, showing evidence in favor of the theory of biogenesis. The experiment he proposed consisted of filling nutrient solution into long-necked S-shaped flasks. This silhouette allows air to enter but not microorganisms, since they are trapped in the curve. After filling, the flask was heated to remove any microorganisms that were already present in the solution.

The result was that the solution remained unchanged for weeks, but if the neck of the flask was broken, then within a few days the sample would be contaminated. With this, it was evidenced that the microorganisms that grow in inert matter have actually been attracted by the air, and not that they will be generated spontaneously.

• You may be interested: "The 30 best phrases of Louis Pasteur"

The theory of biogenesis and its relevance

As I have already advanced, the theory of biogenesis is not very mysterious, although it is easy to see in the case of the births of animals, it was not so easy to understand in other areas, such as the case of the putrefaction.

Even so, the theory of biogenesis does not explain the origin of life, since has no way of telling what the first living organism was. For this reason there are other theories about the origin, many of them are abiogenesis, that is, that the origin of life was from inorganic matter, but only the beginning. There are even the theories of exogenesis, that life came from outside the planet Earth. In any case, the origin of life is still a mystery.