In the late nineteenth century, several German scientists, namely Liebig, Richter, and Helmholtz, attempted to explain the emergence of life on Earth with the hypothesis that it had been brought from elsewhere in the universe in the form of resistant spores in meteorites - Cosmozoic theory.
The presence of organic matter in meteorites found on Earth has been used as an argument in favor of this theory, which does not invalidate the possibility of terrestrial contamination after the meteorite collapse.
The existence of organic molecules in space, such as formaldehyde, ethyl alcohol and some amino acids, has already been proven. However, these molecules appear to form spontaneously without biological intervention.
The Swedish Physicist Arrhenius He proposed a similar theory that life originated in spores propelled by light energy from a "wave" of outer space. Called this theory Panspermia (seeds everywhere). Nowadays these ideas have fallen into disrepute, as it is difficult to accept that any spore can withstand radiation from space, warming the atmosphere, etc.
Nevertheless, in the 1980s of this century, Crick (one of the discoverers of DNA structure) and Orgel suggested a theory of Directed Panspermia, where the initial agent of life on Earth would become colonies of microorganisms, carried on an unmanned spacecraft launched by any very advanced civilization. Life on Earth would have arisen from the multiplication of these organisms in the early ocean.
Despite all the goodwill involved, none of these theories truly advance the problem as it merely shifts the issue elsewhere, not answering the fundamental question: How did life come about?
However, a fundamental breakthrough has occurred with the theories of Pasteur it's from Darwin, allowing you to approach the problem from a different perspective.
Data from various fields of science allowed in 1936 that the Russian Alexander Oparin A revolutionary theory is formulated, trying to explain the origin of life on Earth without resorting to supernatural or extraterrestrial phenomena. Your hypothesis boils down to the following facts:
- In the primitive atmosphere of our planet, there would be methane, ammonia, hydrogen and Steam. Under high temperatures, in the presence of electric sparks and ultraviolet rays, these gases would have combined to give rise to amino acids that floated in the atmosphere. With the moisture saturation of the atmosphere, rains began to occur. The amino acids were dragged into the soil. Subjected to prolonged heating, the amino acids combined with each other to form proteins.
- The rains washed the rocks and carried the proteins to the seas. A "protein soup" in the warm waters of the early seas. The proteins dissolved in water formed colloids. The colloids interpenetrated and originated the coacervated. The coacervates comprised nucleoprotein molecules. They were then organized into droplets bounded by lipoprotein membrane. The first cells appeared. These pioneer cells were very simple and did not yet have an enzymatic equipment capable of photosynthesis. They were therefore heterotrophic. Only later did the more evolved autotrophic cells appear. And that allowed the emergence of aerobic breathing beings.
- Today, the chemical composition of our planet's primitive atmosphere is being discussed, preferring some to admit that instead of methane, ammonia, hydrogen, and water vapor, carbon monoxide, carbon dioxide, molecular nitrogen, and water vapor existed.
Oparin was unable to prove his hypothesis. But in 1953, Stanley Millerat the University of Chicago conducted an experiment in the laboratory. Put in a glass flask: methane, ammonia, hydrogen and water vapor. He subjected them to prolonged heating. A high-voltage electric spark continually cut through the environment where the gases were contained. After a while, Miller has proven the appearance of amino acid molecules inside the balloon, which accumulated in the U-tube.
Shortly thereafter, in 1957, Sidney Fox subjected a mixture of dried amino acids to prolonged heating and demonstrated that they reacted with each other, forming peptide chains, with the appearance of small protein molecules.
The experiments of Miller and Fox proved the truth of Oparin's hypothesis.