Biogenetic principle

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Illustration of the basic biogenetic rule in George Romanes (1892), simplified from Ernst Haeckel's Anthropogenie (1874). Eight different vertebrates are shown from left to right, each in three embryonic stages . Another example of the basic biogenetic rule would be the metamorphosis of the frogs , which are descended from exclusively aquatic ancestors.

The Biogenetic Basic Rule (older also Biogenetic Basic Law ) is one of Ernst Haeckel's 1866 in General Morphology. II: General developmental history of organisms published thesis that a certain relationship between the development of the individual organism ( ontogeny ) and its tribal development ( phylogeny claimed). It says: "Ontogeny recapitulates phylogeny."

A fundamental connection between ontogeny and phylogeny cannot be disputed, since the DNA is to be seen on the one hand as the blueprint of the individual living being and on the other hand as the information-theoretical protocol of the tribal history. Haeckel's thesis of repetition ("recapitulation") goes much further.

The term principle is common in German-speaking countries, otherwise the expression is recapitulation used (English recapitulation theory ). Their claim to be a biological law is now considered refuted. However, it describes the phenomenon that can be observed again and again that the embryos of two different animal species are more similar than the adult organisms. It has therefore not lost its heuristic significance to this day. It is also repeatedly taken up by modern disciplines such as evolutionary psychology or molecular genetics .

history

Ernst Haeckel established the basic biogenetic rule from 1866

In almost all of Haeckel's writings that follow his work General Morphology and deal with evolution, Haeckel summarized the "theses of the causal nexus of biontic and phylogenetic development", i.e. the basic biogenetic rule, as follows:

"Ontogenesis is a short and quick recap of phylogenesis , conditioned by the physiological functions of heredity (reproduction) and adaptation (nutrition)."

Or:

“The germinal development is a compressed and shortened repetition of the tribal development; the repetition is all the more complete, the more the original initial development is retained through constant inheritance, on the other hand the repetition is the more incomplete the more the later disturbance development is introduced through changing adaptation. "

This hypothesis has long been considered an essential part of phylogenetics and has had outstanding heuristic importance for exploring the actual relationships between ontogeny and phylogeny. From a historical perspective, Haeckel's thesis concretized the so-called “law of the corresponding stages” of the German embryologist Karl Ernst von Baer , Baer's rule .

A strict implementation of the postulated recapitulation is not given due to the multiple adaptations of larvae and other developmental stages to the respective environment and to the requirements of cell and organ differentiation. That is why one no longer speaks - if at all - of the basic biogenetic law , but of the basic biogenetic rule , in the non-German-speaking area only of the recapitulation theory . It does not apply to the genotype , that is, the genetic determination of a living being, but - if it is accepted at all - only to the phenotype , that is to the external appearance.

With the opponents of the theory of evolution, the basic biogenetic rule as proof of the evolutionary process has always been rigorously under fire. But even Haeckel himself was not always free from polemics in his arguments .

Examples

Examples of the relationship between ontogeny and phylogeny can be found in most multicellular animals and - to a limited extent - also in plants :

  • Some primordial mouths (protostomia) and new mouths (deuterostomia) form a bladder germ ( blastula ) into which the primeval intestine ( archenteron ) sinks. The resulting ( gastrula ) stage is anatomically similar to a hollow animal .
  • Humans and other mammals also develop cleft gills in the neck region a few weeks after fertilization , some of which are converted into the hyoid bone , for example . Some critics believe that the interpretation of these untrained organs as "gills" is inadmissible. But there is no conclusive alternative interpretation for these structures, which occur exactly where gills would be expected. The gill hypothesis is supported by the matching blood vessel system and nerve supply to the gill arches.
  • Another example of mammals would be the embryonic remodeling of the primary ("reptile") temporomandibular joint into the hammer-anvil joint of the middle ear and the formation of the secondary mammalian temporomandibular joint.
  • The notochord , as found in lancet fish , is placed in front of the spine .
  • The fetus has hair all over its body, called lanugo hair .
  • The human embryo has a caudal spine that is almost as large as a corresponding pig embryo and is only reduced later.
  • Flatfish larvae, such as plaice or flounder , have eyes on either side of their bodies, just like other fish. Only in the further development does an eye wander on the future upper side.

Interpretations and explanations

In addition to the classic recapitulation theory, as represented by Haeckel, there is a weaker version, Baer's rule . This rule from 1828, also known as the “Law of Corresponding Levels”, preceded the recapitulation theory by almost 40 years. Essentially, it says: "The larvae or embryos of two different species are more similar to each other than adult specimens of the same species."

Von Baer wrote about vertebrate embryos at the time: “I absolutely cannot say which class they belong to. It can be lizards, small birds or very young mammals, so complete is the equality in the shape of the head and torso in these animals. "

The biologist Gregory Bateson took up this idea again in his book Mind and Nature . Although there are obvious deviations from this rule (insect larvae, for example), it still provides an important key to the evolutionary process. He generalized the statement on the formulation that "similarities precede differences in time". He also provided an explanation for why that should be the case: evolutionary selection for a genetic mutation is conservative. A mutation that affects the embryonic stage tends to be eradicated faster than a mutation that does not take effect until later in the adult stage. "The change that has an impact earlier in the life of the embryo must disrupt a longer and correspondingly more complex chain of later events."

More recently, the theory of recapitulation has been re-discussed in the context of the Hox genes discovered in the 1970s . These genes are very old and complex genes that define very general body structures and that appear in the same form in animals of the most varied of species. These genes intervene relatively early in embryonic development. The Berlin evolutionary biologist Carsten Niemitz writes : “It is impressive to see how those unimaginably old genes convert their information into a living form, as if we were something like lancet fish that don't even have a head, or even simpler tiny sea animals. "

The embryo controversy

→ Main article: Embryo controversy

Soon after their publication, a scientific controversy arose in which the images were considered to be far too schematic, or even falsified, about the images that Haeckel used to prove the law he postulated as well as to illustrate and explain it in a popular way , were rejected. The controversy was largely forgotten after Haeckel's death, but was again brought to the public's attention by a publication in 1997. The allegations received a great deal of attention, especially from creationists, who (incorrectly) assumed that the basic biogenetic rule, which has not played a special role in the technical field for a long time, was central evidence of the correctness of the theory of evolution.

Counterfeit allegations

As early as 1868, the zoologist and anatomist Ludwig Rütimeyer Haeckel first accused Haeckel of having falsified his illustrations, and this accusation was repeated several times in the following decades.

Michael Richardson of St. George's Hospital Medical School in London pointed out in 1997 that there were serious differences in embryos from marsupials, tree frogs, snakes and alligators, so that he could hardly imagine that Haeckel's drawings were real. He thinks they are fraud.

The geneticist and Nobel Prize winner Christiane Nüsslein-Volhard said in an interview:

“Ernst Haeckel faked it. Many of his pictures of organisms are simply made up to confirm his theory ... "

Science historians point out, however, that Haeckel's drawings, which are mostly presented in the discussion, are largely based on sketches by his predecessors (e.g. von Baer 1828) without being accused of forgery (even details and the posture of individual limbs are often identical ). Haeckel's descriptions therefore represented the perception at the beginning of the 19th century. Haeckel & Co. also presented the embryos prepared, without the yolk sac and appendages - usually described in the blurb of the panels, sometimes also in the text - while the photos used for comparison often show them.

The “schematized” images that were probably meant in the attacks at the beginning of the 20th century can be found in Haeckel's creation story (Berlin 1879, between pages 272 and 273).

Creationists and the basic biogenetic law

Haeckel was bitterly opposed by numerous representatives of the Christian churches, who perceived his positions as an aggressive transgression of boundaries in the area claimed by them , because of his worldview, which he called monism and which was often sharply presented. In this debate, the basic biogenetic rule (then called the “basic biogenetic law”) played an important role. A Christian organization called the Keplerbund took up the accusations renewed in 1907 by the zoologist Arnold Braß of having forged some of the embryo images and made them public. Thereupon a fierce battle raged in the daily press for “Haeckel's embryo images”. Haeckel admitted that he had schematized some pictures, which is common in science: "... I just want to start with the remorseful admission that a small part of my numerous embryo pictures (maybe 6 or 8 out of a hundred) really (in the sense by Dr. Braß) are 'falsified' - namely, all those for which the available observation material is so incomplete or insufficient that one is forced to fill in the gaps with hypotheses when establishing a coherent development chain ”. This campaign concluded with a declaration signed by numerous German biologists and anatomists. In it Haeckel is accused of schematizing as wrongdoing, but his interpretation is recognized as correct. The researchers referred to more recent embryological studies that are far more accurate than the material used by Haeckel.

Both the Keplerbund and the Monistenbund (a free-spirited association that went back to Haeckel) published documentation about the campaign.

The basic biogenetic law plays an important role in many creationist writings and receives more attention there than in scientific biology. The religiously motivated campaign against Ernst Haeckel and "his" basic biogenetic law or the theory of evolution was first heard in 1909 following a keynote lecture by Haeckel on the fiftieth return of Charles Darwin's work The Origin of Species .

Scientific criticism

Already the botanist Carl Wilhelm von Nägeli (1817–1891) accused Haeckel of equating the term ontogenesis with embryonic development or the ascending phase of individual development and at the same time excluding relevant phenomena such as the generation change in plants. Also the idea is wrong that in the individual development new stages are increased to the compressed and more or less disturbed recapitulation of the phylogenesis. Rather, profoundly transformative changes of evolutionary importance can occur at any stage of ontogeny.

Even Stephen Jay Gould's book Ontogeny and Phylogeny is critical of the theory and trying to "drive out the spirit Haeckel, so evolutionary developmental biology can be discussed without having to deal with, biogenetic law '". He also criticizes Haeckel's reference to Lamarck and his theories. Haeckel, on the other hand, saw no indissoluble contradiction in the theories of Goethe, Darwin and Lamarck (see Haeckel's works The History of Creation and General Morphology ).

In 2016, researchers at the University of Pennsylvania found on the basis of 350 million year old fossil finds, from embryos to juveniles, from Aetheretmon fish that the development of this prehistoric fish does not differ from that of today and thus questioned the basic biogenetic rule.

Recap in evolutionary and developmental psychology

Attempts were made to transfer the recapitulation theory to developmental psychology and human cultural development. According to this, children should go through stages of human cultural development in the course of their socialization. These approaches have long been considered a failure, especially since they were ideologically instrumentalized to prove, for example, that some cultures are in a more advanced stage, while others are in a "primitive" stage. However, recent research in the field of evolutionary psychology and cognitive archeology at least points to parallels between the cognitive evolution of humans and the cognitive development of children. This applies, among other things, to cognitive performance and characteristics such as language, music, symbolic thinking and, in general, the interaction of the cognitive modules . However, according to the human ethologist and psychiatrist Gerhard Medicus , the phylo- and onto-genetic parallels mentioned are merely steps of development from the simple to the complex. “Detours” according to the biogenetic rule, such as those found in the gill arches or in the primary and secondary temporomandibular joint (see above), do not exist in the child's psychomotor development.

See also

literature

Primary literature

  • Haeckel Ernst: General Morphology. I: General anatomy of organisms. II: General history of development of organisms . Berlin 1866.
  • Ernst Haeckel: Sandalion . An open answer to the Jesuits' forgery charges. 1-5 Thousand. New Frankfurter Verlag GmbH, Frankfurt a. M. 1910.

Secondary literature

  • Erich Blechschmidt : How does human life begin? From egg to embryo . Stein am Rhein 1989, ISBN 3-7171-0653-8 .
  • Stephen Jay Gould: Ontogeny and Phylogeny . Harvard University Press, 1977, ISBN 0-674-63941-3 .
  • Reinhard Junker: Similarities, rudiments, atavisms . Hänssler-Verlag, Holzgerlingen 2002, ISBN 3-7751-3827-7 .
  • Werner A. Müller, Monika Hassel: Developmental and reproductive biology of humans and animals. An introductory textbook . Berlin 2005, ISBN 3-540-24057-8 .
  • Christiane Nüsslein-Volhard : The becoming of life. How genes control development . Munich 2004, ISBN 3-406-51818-4 .
  • Wilhelm Teudt : In the interests of science. Haeckel's fakes and the 46 zoologists . Scientific publishing house of the Keplerbund, Godesberg 1909.

Individual evidence

  1. ↑ Ernst Haeckel: General Morphology of Organisms. 2 volumes. Berlin 1866 (digital copies: Vol. 1 , Vol. 2 ).
  2. ↑ Gregory Bateson: Geist und Natur , 1982, pp. 208 ff.
  3. ↑ Carsten Niemitz: The secret of the upright gait , 2004, p. 128 ff.
  4. ↑ Interview with Christiane Nüsslein-Volhard at Die Zeit .
  5. ^ Robert J. Richards: The Tragic Sense of Life. Ernst Haeckel and the Struggle over Evolutionary Thought , 2008, p. 303 ff.
  6. ^ A b Dietrich von Engelhardt (1980): Polemics and controversies about Haeckel. Medical History Journal 15 (3): 284-304. online at JSTOR
  7. ↑ Berliner Volkszeitung of December 29, 1908.
  8. ^ Ernst Haeckel and the Biogenetic Law , in Scott F. Gilbert: Developmental Biology . Eighth Edition, 2006.
  9. ↑ Deutschlandfunk: "Fossils question basic biogenetic rules". Retrieved January 13, 2017 .
  10. ^ Steven Mithen: The prehistory of the mind , 2003, pp. 66-68, ISBN 0-7538-0204-X .
  11. ^ ST Parker, KR Gibson: A developmental model for the evolution of language and intelligence in Early Hominids . In: Behavioral and Brain Sciences Volume 3, 1979, pp. 367-408.
  12. ^ Gerhard Medicus (1992): The Inapplicability of the Biogenetic Rule to Behavioral Development. Human Development 35 (1): 1-8. doi : 10.1159 / 000277108

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