Biogenesis theory: explaining the emergence of life

This theory put an end to the belief that life forms spontaneously.

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

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

At the beginning: the theory of spontaneous generation.

The truth is that we cannot talk about biogenesis without first mentioning the model that it ousted from the scientific and popular panorama. 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 a great 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 its origin to Ancient Greece, from the hand of Aristotle; the philosopher argued that some forms of life could appear without further ado from inert matter. For example, worms emerged from mud heated by the sun, or flies from rotting flesh.

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

Redi's experiment

This researcher devised an experiment to demonstrate that insects are not spontaneously generated. To do so, he put different types of meat in eight glass jars, leaving four of them completely uncovered, while the other half were covered with gauze, which allowed air to pass through but not insects.

After a few days, the uncovered meat showed larvae, while the covered meat apparently harbored no life. The result of the experiment showed that it is necessary for the flies to lay their eggs in the meat in order for others of their species to appear. It is an experiment that is linked to the theory of biogenesis and that would have been a success in overthrowing spontaneous generation if it were not for the discoveries of the Dutchman Anton Van Leeuwenhoek, the father of microbiology.

Leeuwenhoek, a few years after the Italian carried out his research, repeated Redi's experiment, but this time he examined the meats with a microscope. In both uncovered and covered meats, microorganisms could be observed, a result that maintained as feasible the ideas of spontaneous generation at least for these living organisms.

Pasteur's experiment

The theory of spontaneous generation endured a couple of centuries more, although there were earlier attempts to disprove it, such as those made by the priest Lazzaro Spallanzani, who demonstrated that if a container with broth is carefully closed and heated, no microorganisms grow; but the supporters of the orthodoxy of the time blamed this on the fact that it had killed all life by heating it.

It was not until 1861, when French chemist Louis Pasteur demonstrated unequivocally 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 flasks in the shape of an S. This silhouette allows air to enter but not microorganisms, since they are retained in the curve. After filling, the flask was heated to eliminate any microorganisms already present in the solution.

The result was that the solution remained unchanged for weeks, but if it broke the neck of the flask, then within a few days the sample was contaminated. This showed that the microorganisms growing in the inert matter had actually been attracted by the air, and not that they were generated spontaneously.

The theory of biogenesis and its relevance.

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

Even so, the theory of biogenesis does not explain the origin of life, since it has no way of indicating what the origin of life was. has no way of indicating what the first living organism was.. Therefore, 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 theories of exogenesis, that life came from outside the planet Earth. In any case, the origin of life is still a mystery.