Pangenesis theory

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Charles Darwin 1868

Pangenesis is a term from genetics and was the methodological approach of Charles Darwin in his work "The variation of animals and plants under domestication ", which he ran in 1868. Like preformation theory, it is one of the historical theories of heredity. It assumes that the germ cells form the reservoir for components of the whole body.

prehistory

The hypothesis, also known as panspermia or pangenesis theory , has been known since ancient times:

The seed goes out from the whole body; healthier of healthy parts and sicker of diseased parts. ( Hippocrates , approx. 460-370 BC)

The Pangenesis theory of Charles Darwin

Darwin developed the pangenesis theory in his later works as a concession to representatives of Lamarckian views because of certain adaptation phenomena in living beings, which he believed he could not explain with his selection theory:

“It is almost universally admitted that the cells or units of the body reproduce by division or prolification, first maintaining the same nature, and finally being transformed into the various tissues and substances of the body. But apart from this mode of multiplication, I suppose that the cells, before they are transformed into completely passive or 'formed substances', give off small granules or atoms which circulate freely throughout the body and which, when supplied with proper nourishment, multiply by division and can later be developed into cells like those from which they originate. For the sake of clarity, these granules can be called cell germs, or, since the cell theory is not fully founded, simply germs [...] Finally, I suppose that the germs in their dormant states have a mutual relationship to one another, which leads to their aggregation either into buds or leads to the sexual elements. To be more precise, it is not the reproductive elements, not even the buds, that create new organisms, but the cells themselves throughout the body. These assumptions form the provisional hypothesis that I have called Pangenesis. "

The following quote clearly shows that Darwin thought far more Lamarckian in the sense of an inheritance of acquired properties than is assumed today: “With variations which are caused by the direct action of changed living conditions [...] the tissues of the body are, according to the theory of the Pangenesis are directly affected by the new conditions and consequently give off modified offspring, which, with their recently acquired peculiarities, are passed on to the offspring. [...] "

Pangenesis theory versus germplasm theory

Concerns about this pangenesis theory arose initially from experimental findings. For example, Francis Galton , a cousin of Darwin's, tried to prove his theory. To do this, he transferred blood from rabbits not colored gray to gray ones in the expectation that the offspring would be piebald. This attempt turned out negative and so from 1876 Galton came out against the somatic induction theory, which postulates that the germ cells can be specifically influenced by the soma. Instead, he advocated the hypothesis of the independence of the genome from the soma, the theory that the Freiburg zoologist and main exponent of neo-Darwinism August Weismann had formulated in 1892 as the germplasm theory . From 1886 to 1895, Weismann and the English philosopher Herbert Spencer fought a bitter, internationally acclaimed scientific dispute about the "factors of organic evolution" which included the theory of pangenesis.

The historical scientific merit of this germplasm theory by Weismann is to have shaken and refuted the assumption that germs originate in the whole body, i.e. the pangenesis theory. Thus, the tough advocates of the assumption of the "inheritance of acquired traits" - such as Herbert Spencer - lost one of their main arguments.

literature

  • Pangenesis theory. In: Lexicon of Biology . tape 6 . Herder, Freiburg im Breisgau 1986, ISBN 3-451-19646-8 , p. 285 .
  • Pangenesis theory. In: Erwin J. Hentschel, Günther H. Wagner: Dictionary of Zoology . 7th edition. Elsevier - Spektrum Akademischer Verlag, Munich 2004, ISBN 3-8274-1479-2 , p. 395 .
  • Pangenesis theory . In: Brockhaus Encyclopedia . 19th edition. tape 16 . FA Brockhaus, Mannheim 1991, ISBN 3-7653-1100-6 , p. 478 .
  • Pangenesis. In: Deutscher Taschenbuch Verlag, Lexikon, editorial staff of the FA Brockhaus publishing house (ed.): Dtv - Brockhaus Lexikon. in 20 volumes, Volume 13: Neo – Par. Mannheim / Munich 1989, ISBN 3-423-03313-4 , p. 315.

Web links

Wiktionary: Pangenesis theory  - explanations of meanings, word origins, synonyms, translations

Footnotes

  1. ↑ Britta-Juliane Kruse: Panspermie (Pangenesis theory). In: Werner E. Gerabek , Bernhard D. Haage, Gundolf Keil , Wolfgang Wegner (eds.): Enzyklopädie Medizingeschichte. De Gruyter, Berlin / New York 2005, ISBN 3-11-015714-4 , p. 1095 f.
  2. ↑ Charles Darwin: The Varying of Animals and Plants in the State of Domestication. (translated by Victor Carus ), 2 volumes, Stuttgart 1868, Volume II, p. 491 f.
  3. ↑ Charles Darwin: The Varying of Animals and Plants in the State of Domestication. (translated by Victor Carus), 2 volumes, Stuttgart 1868, Volume II, p. 517.
  4. ↑ August Weismann: The germ plasma. A theory of inheritance.
  5. ↑ Herbert Spencer: The factors of organic development. In: Kosmos. 10 (1886), pp. 241-272, 321-347. (In English: The factors of organic evolution. In: The Nineteenth Century. 21 (1886), pp. 570-589, 749-770)