Spontaneous generation

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Spontaneous generation or spontaneous generation , also called abiogenesis or archigenesis , Latin generation spontanea , Greek γένεσις αὐτόματος (génesis autómatos) describes the idea that living beings can arise from previously inanimate matter . In ancient times and in the Middle Ages , it was assumed that this was a normal biological process that was assumed to be constantly occurring everywhere. In this sense, Aristotle viewed spontaneous generation as the third way in which living beings came into being, alongside sexual and vegetative reproduction, which was confirmed primarily in the supposed emergence of insect larvae and other arthropods from putrid or dirty matter. Medieval biology followed on from his teaching. This theory was refuted in the 18th and 19th centuries.

The modern hypothesis of chemical evolution is a special case . It concerns the origin of life before the start of biological evolution. The prerequisite was the reducing earth atmosphere that existed about 4 billion years ago . Therefore, spontaneous generation no longer takes place here.

term

The term "spontaneous generation" (γένεσις αὐτόματος) was introduced by Aristotle as a term for the emergence of living beings from inanimate matter. The Latin-speaking scholars of the Middle Ages mostly spoke of generatio ex putrefactione (arising from rot). The German term is first documented by Johann Gottfried Herder , who used it in the form of “original generation” in his writing Aelteste Urkunde des Menschengeschlechts (1774). “Urzeugung” was introduced as a technical term by Samuel Thomas von Soemmerring and Friedrich Wilhelm Joseph Schelling .

Antiquity

In the cultures of antiquity, the origin of life was understood as the creation or procreation of the first living beings by gods or as divinely regarded natural forces and represented in myths . Among the first Greek philosophers , the pre-Socratics , it was primarily Empedocles who grappled with the question of the origin of life. He traced the natural processes back to six principles: four primary substances (fire, air, water and earth) and two forces acting simultaneously on the primary substances: love, which ensures that the primary substances are mixed, and the conflict that separates the primary substances. In some periods of the earth's history love dominates, in others arguing. Empedocles explained the physical and biological processes through the varying degrees of mixing of the elements, which is a result of the temporary dominance of love or quarrel. In this context he developed an idea of ​​biological evolution, assuming the two forces love and strife as well as chance as determining factors. Initially, from the chaos of the differently mixed raw materials, not entire living beings would have formed, but only individual limbs and organs of animals and plants. In a later phase the limbs grew together, resulting in grotesque phantasy structures. It was only at an even later stage that such processes resulted in well-mixed “holistic forms”, including reproductive organisms, the components of which happened to be combined as if they had been created according to plan for a specific purpose. These appropriately designed and equipped creatures have survived and prevailed, while the monsters have proven to be unable to survive and perished.

Aristotle (384–322 BC), who dealt intensively with the doctrine of Empedocles, became the founder of the doctrine of spontaneous generation for the subsequent period. He assumed that certain types of lower animals arise spontaneously in water or in the earth under the influence of heat, air and water as products of putrefaction and putrefaction. He counted clams, jellyfish, snails, crabs, worms, insects and even eels among these species. He described this process as a "boiling" ( pépsis ). His thought was that when liquid matter is heated, it is supplied with the life principle of heat; this gives it the ability to produce life by itself. In sexual reproduction, on the other hand, the task of imparting warmth falls to the seed.

Other species were later mentioned in ancient literature to which such origins were attributed: It was said that lice arise from sweat , scorpions, wasps, snakes and mice from carrion and maggots from rotting cheese. The Christian church fathers adopted this idea and tried to bring it into harmony with the biblical doctrine of creation.

middle Ages

In the Middle Ages the spontaneous generation, for the occurrence of which the authority of Aristotle vouched, was not doubted. Both in the Islamic world, where the philosophy of Aristotle was widely received, and in Europe, spontaneous generation was considered a fact.

In the Islamic world, Aristotle's spontaneous conception was accepted, but when it was explained, there were deviations from Aristotelian teaching. In the 11th century, the Persian scholar Avicenna, like Aristotle, started from the eternity of the world, which he explained in Islam as an eternal creation. He said that matter is constantly being shaped by an immaterial “giver of forms” who gives it a certain shape as soon as a suitable mixture is created in the constantly re-mixing matter. This could also occur outside the body of a reproducing individual, and then it would be a matter of spontaneous generation. In this sense, Avicenna even accepted the possibility of spontaneous generation for humans. Averroes disagreed in the 12th century ; He also believed in spontaneous generation, but for him celestial influences took over the role of cause, which Avicenna had assigned to the giver of forms. A problem for Averroes, who was an Aristotelian, was the Aristotelian principle that in nature like arises only from like. Because of the violation of this principle during spontaneous generation, he considered the creatures created in this way to be unnatural.

In Europe in the 13th century Thomas Aquinas followed the theory of Averroes that in spontaneous generation the power of the sun and the other celestial bodies take the place of the formative power, the carrier of which is the seed during sexual reproduction. In contrast to Averroes, however, he did not consider the creatures created in this way to be unnatural.

In the 14th century, the scholastic Blasius of Parma denied the historical correctness of the conventional view that Noah saved all animal species in his ark during the Flood . This was not feasible because the various animal species were sometimes incompatible with one another. It is therefore more plausible to assume that after the Flood there was a new emergence of species through spontaneous generation.

Early modern age

In the Renaissance , as in the Middle Ages, scholars followed Aristotle's idea of ​​spontaneous generation. Spontaneous generation has even been considered as an alternative to the biblical account of the creation of the first man, Adam . In the early 16th century, Tiberio Russiliano took the view that the indigenous peoples of America must have arisen spontaneously because they could not have reached their settlement areas by boat. If you look at the question in terms of natural philosophy ( phisice , i.e. not theological), this can also be assumed for the first person on earth.

Another representative of spontaneous generation was Johan Baptista van Helmont . He recommended an experiment to make mice as evidence: if you stuff a dirty shirt into the opening of a jar filled with wheat grains, the smell changes after about twenty-one days. According to Helmont, the decomposition products would now penetrate the husk of the wheat and transform the wheat into mice.

In the 17th century, Pierre Gassendi explained spontaneous generation as part of his materialistic atomism . He attributed the existence of living beings to the existence of a combination of atoms suitable for life; Such a combination is not only possible in the body of an already existing, reproducing being, but in principle also outside. Therefore, new life can also arise in the earth from inanimate matter.

Francesco Redi

A counter-movement against the theory of spontaneous generation emerged in the 17th century when the principle “ Omne animal ex ovo ” (German: “Every animal emerged from an egg”) began to spread. A leading proponent of this hypothesis was the Italian doctor Francesco Redi (1626–1697). By means of an experiment in 1668, he refuted the widespread view that maggots arise spontaneously in rotting meat. He took three pots and filled them with meat. He closed one pot completely. He left the second pot open and covered the third pot with gauze . Maggots only appeared in the open, but not in the closed pot. He found developing maggots on the gauze of the third pot. Because of their small size, the eggs of the flies were invisible to the naked eye. In the same year Redi published the essay Esperienze intorno alla generazione degli insetti . Redi's experiments are considered to be the first precisely executed pair of experiment and counter-experiment in the history of biology.

On the basis of observations on fungi, Luigi Ferdinando Marsigli and Giovanni Maria Lancisi in their study Dissertatio de generatione fungorum ( Treatise on the origin of fungi ) contradicted the view, which has been widespread since ancient times, that fungi arise from putrefaction, whereby the mycelium is an intermediate stage between rotting plants and the mushrooms.

After the discovery of various microorganisms , the theory of spontaneous generation was revived. In the 18th century, the English priest John Turberville Needham (1713–1781) and Georges-Louis Leclerc de Buffon (1707–1788) experimented with heated meat broth in closed vessels, whereby they were able to detect organisms that had apparently developed spontaneously, so-called infusoria . Charles Bonnet (1720–1793) assumed that microorganisms could get into the vessels used through “invisible openings”. In 1768, Lazzaro Spallanzani finally proved that no living beings emerged from sterile test material. Spallanzani cooked the broth for 45 minutes and immediately sealed the jar. Even after several days he could not find any new organisms. Only after opening the vessels could they be observed again.

In philosophy in the 18th century the increasingly corroborating experimental evidence for the assumption that the living arises only from the living was used as an argument for the assertion that life cannot arise without divine intervention. Scouts like Voltaire agreed. Atheist philosophers like La Mettrie and Holbach , on the other hand, stuck to the spontaneous generation hypothesis. The results of Needham and Buffon provided a basis for argumentation for this.

Modern

In the 19th century u. a. Experiments by Louis Pasteur in 1861 that even microorganisms show no spontaneous generation. In 1864 Pasteur published the principle Omne vivum e vivo ( Latin for 'everything living comes from living'). Franz Schulze, Theodor Schwann and Heinrich Schröder also contributed to the refutation of the spontaneous generation hypothesis . The English physicist John Tyndall (1820–1893) was finally able to dispel all doubts with his theory of the heat-unstable and heat-stable phases ( spores ) in bacteria.

The sentence “Everything living arises from living things” contradicts the generally accepted standard model of cosmology , according to which (inanimate) matter did not even exist at the beginning of the universe (at the Big Bang ), but was formed from energy due to the equivalence of mass and energy . Continued logically , living things could only have arisen from living things that should have already existed at the Big Bang.

The chemical evolution from inanimate matter is still unexplained in detail. It is generally believed to be a process of emergence and self-organization . The Miller-Urey experiment shows the first steps in the production of amino acids , which are considered to be the “building blocks of life”. However, today it is doubted that the conditions for the experiment were ever given on earth.

literature

Web links

Individual evidence

  1. ↑ Source texts with translation and commentary in Geoffrey S. Kirk , John E. Raven , Malcolm Schofield (eds.): Die vorsokratischen Philosophen. Introduction, texts and comments. Study edition. Metzler, Stuttgart a. a. 2001, ISBN 3-476-01834-2 , pp. 333-336.
  2. ^ Hasse: spontaneous generation and worldview. 2006, pp. 16-18.
  3. ^ Hasse: spontaneous generation and worldview. 2006, pp. 8, 34.
  4. ^ Hasse: spontaneous generation and worldview. 2006, p. 8 f., 34.
  5. Reto U. Schneider : The book of crazy experiments. Paperback edition. Goldmann, Munich 2006, ISBN 3-442-15393-X , p. 17.
  6. ^ Hasse: spontaneous generation and worldview. 2006, p. 9.
  7. Francesco Redi: Esperienze intorno alla generazione degli insetti in Italian-speaking Wikisource .