Abiogenesis theory and biogenesis theory
We know that since ancient times people have had the desire to know the world. The more we know about it, the more we can act to improve our lives, understanding that care must be taken not to alter the balance of the environment.
One of the questions that humans, scientists or not, from different cultures and religions have sought (and seek) to answer is this: How did life come about? (Problem). To answer this question, several theories (hypotheses) different ones have already been created.
Regarding the origin of life, among the theories (hypotheses) best known we have:
- The abiogenesis theory, accepted until the mid-nineteenth century, states that life can be spontaneously generated;
- The biogenesis theoryaccording to which life can only be produced by another pre-existing life;
- O creationism, which explains the emergence of life from the will of a divine creator;
- The cosmic panspermia, for which life on Earth originated from living beings from outer space.
To facilitate understanding of when an explanation is scientific, and when it is unscientific, we will present a summary of the scientific work and the debates that were held between the proponents of abiogenesis theory and those of biogenesis theory.
To the Greek philosopher Aristotle (384-322 BC), life was spontaneously generated by an active principle (a type of energy capable of producing life). He defended, therefore, the theory called abiogenesis, whose name comes from the Greek: The (prefix meaning "without"); bio (means "life") and genesis (means "origin").
For centuries, famous sages and physicians such as Paracelsus (1493-1541) and Van Helmont (1579-1644) have been working on Aristotle's theory, that is, considering that life arose spontaneously.
Van Helmont did an experiment to prove this theory: he put in a box a dirty shirt with a lot of sweat and wheat germ. About three weeks later, mouse pups were born. He "proved" thus that the mice had been spontaneously generated, and human sweat would have been the active principle.
Some scientists doubted these claims, saying they were false, and sought to refute them based on experiments. One of them, the Italian biologist Franscesco Redi (1626-1697), formulated a different hypothesis: the theory of biogenesis, according to which life is produced only by pre-existing life.
Redi then researched how insect larvae appeared in decaying flesh and found that fly larvae (which would give rise to new flies) came from eggs laid by adult flies. Thus Redi, to prove his theory, put in pieces two pieces of meat. One of the Redi bottles kept closed and the other opened. In the jar where the capped pieces of meat were placed, no larva appeared because the adult flies did not have access to meat to lay the eggs.
With this experiment, he invalidated the theory of spontaneous generation and proved that his hypothesis was correct: life is only produced by pre-existing life.
Although refuted by Redi, the idea of spontaneous generation still persisted, about a century, to explain the emergence of certain living beings. Many thought that microorganisms (eg bacteria), being simpler than mice and flies, arose spontaneously.
In order for the idea of spontaneous generation to be definitively rejected, the Italian researcher Lazzaro Spallanzani (1729-1799) did an experiment similar to that performed by Redi. He boiled broth in jars and destroyed the microorganisms present there. It kept some vials closed and some open. The microorganisms reappeared only in the opened vials.
Proponents of the theory of abiogenesis contested the results of Spallanzani's experiment, making the assumption that shortness of breath a substance (the active ingredient) that would turn the broth into living things was not present.
It was not until the mid-nineteenth century that the French scientist Louis Pasteur he refuted the theory of abiogenesis (idea of spontaneous generation) with a series of controlled experiments.
- Pasteur put broth in two S-necked glass jars and boiled both broths.
- After cooling the broth he broke the neck and S of one of the flasks allowing the microorganisms to enter the air and grow in the broth.
- In the second vial the neck and S was kept causing microorganisms and dust to remain trapped in the curvature of the neck. Thus air came into the flask, but no new organisms appeared in the broth.
Pasteur concluded from this experiment that microorganisms were present in the air, but if they were isolated they would not spontaneously appear in the broth.
The debate over the theory of spontaneous generation is an example that observations and assumptions can lead to erroneous conclusions and innovative solutions may take many years to accept.
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