Embryo controversy

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Title page of a publication by Arnold Braß directed against Haeckel

The embryo controversy was a dispute over allegations of counterfeiting against the evolutionary biologist Ernst Haeckel . In the Natural History of Creation , published in 1868 , Haeckel tried to popularize the still young evolutionary biology by presenting it to laymen. The was Embryology presented as a central argument: The individual development of an organism that ontogeny , recapitulates the phylogenetic development, the phylogeny ( recapitulation theory must be declared), and was only in the context of an evolutionary model.

This argument was supported by illustrations intended to demonstrate the similarities between embryos of different species . However, some drawings omitted known differences. Other representations were identical copies of a woodcut , but were used to illustrate different species without appropriate information. Such shortcomings were criticized by Haeckel and accusations of falsification from scientific colleagues and the Darwin-critical public.

Haeckel's prominent position in the debates about the theory of evolution led to a broad reception of the controversy. Haeckel was not only the best-known proponent of the theory of evolution in Germany, he also declared his advocacy for Darwinism to be a general ideological battle against traditional biology, "church wisdom and [...] after-philosophy". In this context, Haeckel understood embryology as "heavy artillery in the fight for truth", which contributed to an often hostile reception of his writings.

The embryological reasoning for the theory of evolution

Haeckel's argument for the theory of evolution was based essentially on considerations of ontogenesis, i.e. the biological development of individual organisms from the fertilized egg cell to the adult living being. Two observations convinced him of the paramount importance of embryological research. On the one hand, there are features in embryos that are only rudimentary in adult creatures . For example, a human embryo has a freely protruding tail in the first two months, of which only three to five tail vertebrae remain after birth . "This stunted tail of man is an irrefutable testimony to the undeniable fact that he is descended from torn ancestors."

Illustration of the basic biogenetic law in anthropogeny (1874)

Haeckel's second observation related to the general similarity between vertebrate embryos . He argued that the embryos of all vertebrates were initially indistinguishable and only gradually differentiated different characteristics. The more closely related the species are, the later the differences appear. In Anthropogenie from 1874, Haeckel illustrated this idea with a picture of eight vertebrate embryos in three stages of development each. At the first stage, the embryos of all species are almost indistinguishable. In the second column, specific features of the fish and amphibian embryos can already be clearly seen, while the other embryos only differ in details. Finally, at the last stage, all species are clearly distinguishable. Nevertheless, the four mammalian embryos share many morphological features that clearly distinguish them from the four other vertebrate embryos.

According to Haeckel, these similarities between vertebrate embryos, already described by Karl Ernst von Baer , are only a surface phenomenon that indicates a more fundamental connection between evolution and individual development. At the beginning, the embryos are not only similar, they all have the typical characteristics of the older vertebrates: Even the circles formed “do not know that [the human] embryo at a certain time essentially has the anatomical structure of a fish, later possessed the construction of amphibian forms and mammalian forms, and that with further development of these latter forms first appear which are at the lowest level of mammals ”.

These observations culminated in Haeckel's formulation of the basic biogenetic law , according to which ontogeny is a recapitulation of phylogeny. In its development, the human embryo is supposed to go through the stages of vertebrate evolution in a short and incomplete way. At the beginning of the human embryo, for example, typical fish characteristics such as gill systems are found , which disappear in the course of ontogenetic development. Haeckel regarded this connection as one of the “most important and irrefutable proofs” of the theory of evolution, since non-evolutionary approaches could not offer a plausible explanation of this phenomenon.

Illustrations of the natural history of creation

Alleged representation of a dog, chicken and turtle embryo. The illustrations, however, are identical copies of a woodcut.
Fourth week dog and human embryos (A and B, left); Embryos of human dog, turtle and chicken in the sixth week (C – F, right).

Haeckel's embryological argument for the theory of evolution was made accessible to a broad readership for the first time in the natural history of creation . The presentation of the Biogenetic Basic Law was based on a series of images that were designed as illustrations and evidence of the train of thought.

Three pictures allegedly showed the embryos of a dog, a chicken and a turtle. The identical shape of the representations should convince the reader that the vertebrate embryos do indeed share a common stage of development: “If you compare the young embryos of the dog, chicken and turtle in Figs. 9, 10 and 11, you will not be in the Be able to perceive a difference. ”The correspondence between the illustrations, down to the smallest detail, was only possible because the three illustrations were created using the same printing block. So while the readers should accept the identical appearances as evidence for Haeckel's embryological theses, the apparent proof was generated by identical copies of an image. In later editions, only one illustration was used in response to criticism. However, Haeckel pointed out that the drawing could equally represent a bird or mammalian embryo.

Another illustration served to illustrate the basic biogenetic law at later stages of development. Figures A and B show the embryos of a dog and a human in the fourth week. Figures C – F represent the embryos of dog, human, turtle and chicken in the sixth week. Here, too, the reference to Haeckel's line of argument is obvious: In the fourth week, the embryos are almost indistinguishable. Even by the sixth week, mammalian embryos are very similar, but easily distinguishable from reptiles and birds .

Haeckel did not create his drawings from real embryos, but used illustrations from other textbooks as templates. Since he did not give any sources for his drawings, critics quickly speculated about the origin of the pictures. Ludwig Rütimeyer declared them to be alienated copies of illustrations by Theodor von Bischoff , Alexander Eckers and Louis Agassiz and accused Haeckel of alienating the representations in the interests of his theory. Haeckel did not want to admit any mistake at this point, he explained in a letter: "Besides, the shapes of the same are partly copied from nature, partly compiled from all the images known so far about these stages."

  • Possible template for Haeckel's human embryo. Ecker 1851-1859

  • Possible template for Haeckel's dog embryo. Bischoff 1845

The controversy

Early reactions

Shortly after the publication of the Natural History of Creation , there were discussions among specialists about Haeckel's illustrations. Von Bischoff complained to his colleague Carl von Siebold about what he believed to be too free drawings. He initially defended Haeckel and wrote a letter to Haeckel in 1868, asking for sources for the drawings.

Such doubts, however, were not expressed in public in the first few years and by no means showed the sharpness of the controversy that began in 1874. An exception is the Basel anatomist Ludwig Rütimeyer, who published his criticism in the Archive for Anthropology . Rütimeyer was outraged that Haeckel's drawings were presented as evidence and not as schematic illustrations. This could "not be called anything else than playing games with the public and science". Haeckel reacted extremely irritably to Rütimeyer's allegations. In a letter to Charles Darwin , he interpreted the criticism as an ingratiation to “clerical Basel”, which would now pay for Rütimeyer's salary.

Meanwhile, Darwin and other scientists have had extremely positive responses to the natural history of creation . In the introduction to the descent of man , published in 1871, Darwin wrote with reference to Haeckel's work: “If this book had appeared before my work was written, I would probably never have finished it.” Darwin also spoke up in the conflict with Rütimeyer . In a letter to Haeckel it says: “I was saddened to have read Rütimeyer's review a year or two ago. I am sorry that he is so retrograde, also because I respected him very much. "

From evolution to evolutionary worldview

The natural story of creation proved to be a journalistic success, in 1874 the fifth edition appeared. Darwin's recognition and positive reviews in magazines such as Nature and Das Auslands also helped Haeckel establish himself as a leading representative of Darwinism in German-speaking countries. Haeckel used this attention to propagate an evolutionary worldview in addition to the biological theory of evolution. Darwinism not only has to revolutionize all biological disciplines, but appears as a basis on which “all true science will continue to build in the future”.

Haeckel's claim to a general validity of evolutionary thought also referred to ethics and politics . In the 1870s this was expressed in Haeckel's link between the theory of evolution and Bismarck's cultural struggle against Catholicism . In this sense, in the Anthropogenie published in 1874, Haeckel contrasted the Enlightenment theory of evolution with a “black international” under the “banner of hierarchy: mental bondage and lies, irrationality and rawness, superstition and regression”.

Haeckel's conception of a comprehensive worldview contrasted with Darwin's cautious presentation of the theory of evolution and placed Haeckel at the center of the German debates on the theory of evolution. Catholic theologians and philosophers such as Johannes Huber saw in Haeckel a pioneer of mechanical materialism and declared him to be the “dogmatist of the worst kind”. Sharp criticism was also raised by empirical scientists such as the ethnologist Adolf Bastian . A presentation of the theory of evolution that can be understood by laypeople is to be praised in principle, but Haeckel links biological facts in an unacceptable way with speculations and subjective worldview. Haeckel abuses his scientific authority when he sells metaphysical theses to the reader as facts . “You are the fanatical crusade preacher of a new faith […]. Who knows where you might take it; They have all what it takes to proclaim a dogma of infallibility. "

Wilhelm His

His depiction of a human and a pig embryo. The clearly recognizable morphological differences contradict Haeckel's representations.

The escalating debate about Haeckel's evolutionary worldview remained independent of the embryo images in the early 1870s. This changed when the anatomist Wilhelm His questioned Haeckel's scientific seriousness in the work Our Body Shape and the physiological problem of its origin in 1875 . The richly illustrated publication developed a physiologically oriented embryology that in no way conformed to Haeckel's basic biogenetic law.

Not only were the theories incompatible, His also attacked Haeckel's embryo drawings and his scientific methodology directly. Haeckel's embryo drawings were not only copied from other textbooks, but also falsified by Haeckel. For example, when drawing the four-week-old human embryo, Haeckel did not use a picture of Bischoff alone as a template without citing the source. He also doubled the length of the tail compared to Bischoff's drawing in order to make the human and dog embryo appear more similar. Such procedures disqualified Haeckel as a serious scientist:

“I myself grew up believing that among all the qualifications of a natural scientist, reliability and absolute respect for the truth are the only ones that cannot be dispensed with. [...] So let others in Mr. Haeckel venerate the active and ruthless party leader, in my opinion he himself has renounced his right to be counted among serious researchers as an equal in this way of fighting. "

His was not an opponent of the theory of evolution in general, but did advocate limiting its scope. Successful embryology should not be based on speculative evolutionary comparisons. Rather, it has to orientate itself on the methodical guidelines of the likewise new - and harshly rejected by Haeckel - experimental physiology. The different attitudes towards the scope of evolutionary models pushed Haeckel and His to opposite ends of the Darwinian spectrum. While Haeckel wanted to extend evolutionary arguments from phylogeny to ontogeny to politics and ethics, His advocated the extensive independence of biological disciplines such as embryology from the theory of evolution.

The debate escalated and died down

The sharp criticism of a recognized embryologist brought an additional dynamic into the debate about Haeckel's variant of Darwinism. From now on Haeckel was attacked by his opponents with reference to His as a scientific forger, whose "sad confusions" would have excluded him from the circle of scientists. Attacks came equally from natural scientists who were skeptical of the theory of evolution, or at least Darwin's theory of selection, and from theologians and religious philosophers who viewed Darwinism as a dangerous and materialist ideology .

In the fourth edition of Anthropogeny from 1891, Haeckel finally felt compelled to write an “apologetic conclusion”. With a gap of more than twenty years, Haeckel was quite ready for self-criticism: In the natural creation story , the similarities between the vertebrate embryos were "exaggerated", and the triple use of the same printing block was "extremely careless folly". At the same time, however, Haeckel started a verbal attack on His and his other critics. It is "pathetic", "contemptuous" and "childish" to construct a scientific allegation of falsification from such inaccuracies and errors in detail. His opponents would themselves act dishonestly because they wanted to discredit Darwinism as a whole with their attacks on detailed errors.

The "final apologetic word" came at a time when the embryo controversy was already subsiding. Other debates had come to the fore, such as the controversy between Haeckel and Rudolf Virchow about the introduction of the theory of evolution in school lessons. At the 50th annual meeting of the gathering of German naturalists and doctors , Haeckel called for a far-reaching reform of teaching, while Virchow opposed the teaching of “speculative buildings” such as the theory of evolution. With the bestseller Die Weltträthsel published in 1899 and the Monistenbund founded in 1906 , Haeckel increasingly shifted the controversies surrounding him from the theory of evolution to his general monistic philosophy . The embryo controversy became a marginal issue that Haeckel's opponents occasionally used to question his scientific credibility.

Newer reception

Renewal of counterfeit allegations

Photograph of a human embryo in the 5th week pc (7th week of pregnancy ).

With the First World War , Haeckel's death in 1919 and the dissolution of the Monistenbund by the National Socialists in 1933, interest in Haeckel's theories generally waned, and the embryo controversy was largely forgotten. This only changed in 1997 with the publication of the embryologist Michael Richardson . Richardson and co-workers primarily opposed the idea of ​​an embryonic stage shared by all vertebrates in contemporary research. In doing so, they compared current photographs of embryos with Haeckel's representations, found major differences and stated that the results "would seriously undermine his credibility".

In the same year Science reported on the results in the research news section under the title “Fraud rediscovered”. Now, too, the allegations of counterfeiting sparked a heated debate. Richardson initially declared Haeckel's drawings to be forgeries and later withdrew this assessment with reference to the historical context. In newspapers such as the Times and the Frankfurter Allgemeine Zeitung , the allegations of falsification were partly renewed and partly rejected.

In addition, the re-emerging debate was taken up by representatives of intelligent design to substantiate general doubts about the theory of evolution. Jonathan Wells stated in his article “Survival of the fakest” that the Haeckels case shows that the evidence for the theory of evolution is largely based on simplifications and falsifications that have since been refuted. Michael Behe explained the embryo controversy as an example of the need for a critical approach to the theory of evolution in biology classes .

History and theory of science

In the scientific-historical discussion of the controversy, the falsification allegations against Haeckel are predominantly rejected. A typical assessment can be found, for example, by Nick Hopwood , according to which the current allegations of forgery do not take sufficient account of the historical context and are based on an individualistic understanding of forgery. The allegations were often based on modern standards of scientific work. In the 19th century, for example, in view of the lack of available embryos, it was customary to copy anatomical drawings from other textbooks.

An epistemological interpretation of the conflict between Haeckel and His can be found in the context of a “History of Objectivity ” by Lorraine Daston and Peter Galison . The embryo controversy comes at a time when scientific methodologies are changing . Haeckel is still in the tradition of a science oriented towards "natural truth", in which idealized illustrations were viewed as the central means of scientific work. The task of the scientist is to describe and illustrate the true archetypes behind the variety of phenomena. In contrast, His is a representative of the emerging methodology of “mechanical objectivity”, according to which it is the duty of the scientist to keep the representation as free as possible from his own subjectivity.

In this sense, Haeckel complained that his representations “show the essence of the subject and leave out the inessential; [...] According to His (and many other 'exact' pedants) only the photographer is completely flawless and virtuous ”.

literature

Primary literature

  • Ernst Haeckel: Natural history of creation . 1st edition. Georg Reimer, Berlin 1869 and 3rd edition. Georg Reimer, Berlin 1872.
  • Ernst Haeckel: Anthropogeny . 1st edition. Wilhelm Engelmann, Leipzig 1874.
  • Ernst Haeckel: Apologetic conclusion . In: Anthropogeny . 3rd edition, Wilhelm Engelmann, Leipzig 1891.
  • Wilhelm His: Our body shape and the physiological problem of its formation . F. C. W. Vogel, Leipzig 1875.
  • Ludwig Rütimeyer: Papers. "About the origin and the family tree of the human race" and "Natural history of creation" . In: Archives for Anthropology . No. 3, 1868, pp. 301-302.

Secondary literature

  • Mario A. Di Gregorio: From Here to Eternity. Ernst Haeckel and Scientific Faith . Vandenhoeck & Ruprecht, Göttingen 2005, ISBN 3525569726 .
  • Nick Hopwood: Pictures of Evolution and Charges of Fraud . In: ISIS . Volume 97, 2008, Chicago Journals, ISSN  0021-1753 , pp. 260-301.
  • Nick Hopwood: Haeckel's Embryos: Images, Evolution, and Fraud. University of Chicago Press, 2015, ISBN 978-0226046945
  • Robert J. Richards: The Tragic Sense of Life. Ernst Haeckel and the Struggle over Evolutionary Thought . Chicago University Press, Chicago 2008, ISBN 0226712141 .
  • Michael Richardson and Gerhard Keuck: Haeckel's ABC of evolution and development . In: Biological Reviews . Volume 77, 2002, ISSN  0006-3231 , Blackwell Synergy, pp. 495-528.
  • Klaus Sander : Ernst Haeckel's ontogentic recapitulation: irritation and incentive from 1866 to our time . In: Annals of Anatomy . Volume 184, 2002, ISSN  0940-9602 , Urban & Fischer, pp. 523-533.

Web links

  • Nick Hopwood's homepage , contains numerous texts on Ernst Haeckel and the history of embryology.
  • Biolib , contains biological primary texts, including numerous works by Haeckel.

Individual evidence

  1. ↑ Anthropogeny . 1st edition. S. XIV.
  2. ↑ Natural history of creation . 3. Edition. P. 259.
  3. ↑ Anthropogeny . 1st edition. P. 4.
  4. ^ First formulated in Ernst Haeckel: General Morphology . Georg Reimer, Berlin 1866, volume 2, p. 300, compare also natural history of creation . 1st edition, p. ???
  5. ↑ Natural history of creation . 3. Edition. P. 276.
  6. ↑ Natural history of creation . 1st edition. P. 249.
  7. ↑ Natural history of creation . 3. Edition. P. 271.
  8. ↑ Papers . P. 302.
  9. ^ Ernst Haeckel to Theodor von Siebold, January 4, 1869, Ernst Haeckel Archive, Ernst Haeckel House, Jena.
  10. ^ Theodor von Siebold to Ernst Haeckel, December 28, 1868, Ernst Haeckel Archive, Ernst Haeckel House, Jena.
  11. ↑ Papers . P. 302.
  12. ^ Ernst Haeckel to Charles Darwin, October 12, 1872, Cambridge University Library, MSS.DAR.166: 58.
  13. ^ Charles Darwin: The Descent of Man, and Selection in Relation to Sex , John Murray, London 1871, p. 4.
  14. ^ Charles Darwin and Ernst Haeckel, September 2, 1972, Ernst Haeckel Archive, Ernst Haeckel Haus, Jena.
  15. ↑ Michael Foster: Haeckel's Natural History of Creation . In: Nature . Volume 3, 1870, pp. 102-103. And: Anonymous: Ernst Haeckel's natural creation story 1: The theory of descent . In: Abroad . Number 43, 1870, pp. 673-679.
  16. ↑ Natural history of creation . 1st edition, p. ???
  17. ↑ Anthropogeny . 1st edition. S. XII.
  18. ^ Johannes Huber: Scientific questions of the day I: Darwin's changes and Häckel's “natural history of creation” . In: Allgemeine Zeitung , June 8, 1874.
  19. ^ Adolf Bastian: Open letter to Professor Dr. E. Chop . Wiegandt, Hempel & Parey, Berlin 1874, p. ???
  20. ↑ Our body shape and the physiological problem of its formation . P. 171
  21. ↑ Carl Semper: The Haeckelism in zoology . W. Mauke's Sons, Hamburg 1876, p. 35, note 7.
  22. ↑ An example of internal scientific criticism is Victor Hensen: The plankton expedition and Haeckel's Darwinism: About some tasks and goals of the descriptive natural sciences . Lipsius & Tischer, Kiel 1891. A theological criticism is for example: Friedrich Michelis: Haeckelogonie . P. Neusser, Bonn 1875.
  23. ↑ "Apologetic Closing Word". Pp. 859-861
  24. ↑ "Apologetic Closing Word". P. 862 f.
  25. ^ Rudolf Virchow: Free science and free teaching . Wiegandt, Hempel & Parey, Berlin 1878.
  26. ↑ Exceptions are: Erik Nordenskiöld: Biologens Historia . Bjorck & Borejsson, Stockholm 1920-1924; Richard Goldschmid: The Golden Age of Zoology . University of Washington Press, Seattle 1966, ISBN 0295740434 and Reinhard Gursch: Ernst Haeckel's illustrations on the history of descent and development: Discussion in scientific and non-scientific literature . Lang, Frankfurt a. M. 1981.
  27. ↑ Michael Richardson et al .: There is no highly conserved embryonic stage in the vertebrates: implications for current theories of evolution and development . In: Anatomy and Embryology . Volume 196, 1997, ISSN  0340-2061 , Springer, p. 104.
  28. ↑ Michael Richardson and Gerhard Keuck: Haeckel's ABC of evolution and development . In: Biological Reviews . Volume 77, 2002, ISSN  0006-3231 , Blackwell Synergy, p. 519.
  29. ↑ See for example: Nigel Hawkes An Emryonic Liar . In: Times , Aug. 11, 1997; Joachim Müller-Jung : Attack on biological anachronism . In: Frankfurter Allgemeine Zeitung , August 20, 1997.
  30. ↑ Jonathan Wells: The Survival of the Fakest . In: The American Spectator , December 2000 / January 2001, pp. 19-27.
  31. ↑ Michael Behe: Teach Evolution and Ask Hard Questions. In: New York Times. August 13, 1999.
  32. ^ Hopwood: Pictures of Evolution and Charges of Fraud . P. 261; see. also: Richards: The Tragic Sense of Life . P. 279; Lorraine Daston and Peter Galison: Objectivity . Suhrkamp, ​​Frankfurt a. M. 2007, ISBN 3518584863 , pp. 201-206.
  33. ^ Lorraine Daston and Peter Galison: Objectivity . Suhrkamp, ​​Frankfurt a. M. 2007, ISBN 3518584863 , pp. 201-206.
  34. ↑ "Apologetic Closing Word". P. 859 f.
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