The question of the origin of life is one of the most difficult questions of natural science. There is no exact answer to it, but there are many hypotheses.
1. Hypothesis of the divine origin of life (creationism)
According to this hypothesis, all living organisms on Earth were created by God. They are initially expedient and remain unchanged. Moreover, the creation of the world happened once, so its study is impossible.
Creationism takes life for granted and does not attempt to explain the origin of life by natural laws of nature.
2. The hypothesis of spontaneous origin of life
This hypothesis implies multiple spontaneous emergence of living organisms from nonliving matter. In the Middle Ages, many “managed” to observe the appearance of living organisms (worms, insect larvae, mice, molds) in the decaying remains of organisms.
In 1668, the Italian physician F. Redi experimentally refuted these ideas. He placed pieces of meat in vessels, some of which he covered with gauze. Fly larvae soon appeared in the open vessels, but there were none in the closed ones. This proved the impossibility of spontaneous generation of flies in rotting meat. Redi put forward the principle “all living things are from living things.”
In 1859, the French microbiologist L. Pasteur was able to finally refute the hypothesis of the spontaneous emergence of living organisms. He experimentally established that microorganisms cannot spontaneously appear either. Pasteur placed sterile broth in special flasks with long S-shaped necks. Some of the flasks remained open. Bacteria soon appeared in the open flasks and began to multiply. In flasks with a curved elongated neck, which served as a kind of trap for bacteria, the broth remained sterile.
By the end of the 19th century. practically all scientists have recognized that living organisms arise only from other living organisms.
3. Hypothesis of panspermia
In 1865, the German scientist G. Richter first expressed the idea of the cosmic origin of life on Earth. According to his hypothesis, life was brought in from other planets. Proponents of the cosmic origin of life believe that life was brought to Earth by accident or deliberately by space aliens. But the question of the origin of life in space remains open.
4. Biochemical hypothesis
In 1924 the Soviet biochemist A.I. Oparin and in 1929 the English biochemist J. Haldane put forward the hypothesis that life arose from inorganic substances in the specific conditions of the ancient Earth.
In 1947, the English scientist J. Bernal, based on the Oparin – Haldane hypothesis, formulated the hypothesis of biopoiesis, which characterizes three stages in the formation of life on Earth.