Recapitulation theory

The biogenetic rule ( older also fundamental biogenetic law, in the English language known as recapitulation theory ) is a 1866 drawn up by Ernst Haeckel thesis in biology, which is to express a possible link between ontogeny and phylogeny. In this vagueness Haeckel's theory is in principle not falsifiable, because the DNA is to be regarded both as the information theoretic protocol of phylogeny and the other as the blueprint of ontogenesis. However, Haeckel went from following much more detailed basic assumption: " ontogeny recapitulates phylogeny. "

The term principle is common in German-speaking countries, otherwise the expression recapitulation theory is used because the theory is outdated. Their claim to be a biological law, is now regarded as disproved. However, she describes in the animal world repeatedly observed phenomenon that the embryos of two different species are more similar than the adult organisms. It has therefore not lost to this day your heuristic importance. So it is always taken up by disciplines to which Haeckel could not think of how evolutionary psychology or molecular genetics.

• 6.1 Primary Sources
• 6.2 secondary literature
• 6.3 sources

History

In almost all the writings of Haeckel, who follow his work General morphology and deal with evolution, Haeckel summed up the "Theses of the causal nexus of biontischen and the phylogenetic development ", ie the biogenetic principle, briefly thus:

Respectively:

This hypothesis has long been regarded as an essential part of phylogenetics and had great heuristic significance for the exploration of the actual relationships between ontogeny and phylogeny. Historically concretized Haeckel with his thesis the so-called "law of corresponding stages " of the German embryologist Karl Ernst von Baer, ​​the perches rule.

A strict implementation of the postulated recapitulation is not given to the particular environment and to the needs of the cell and organ differentiation due to multiple adaptations of larvae and other stages of development. Wherefore they say - if at all - not even from the more fundamental biogenetic law, but of the biogenetic rule in the non - German -speaking only of the recapitulation theory. It does not apply to the genotype, that is, the genetic determination of a living being, but - if they are accepted at all - only for the phenotype, that is for the external appearance.

When the opponents of the theory of evolution the biogenetic rule stood as evidence of the process of evolution has always been rigorously under attack. But Haeckel himself was with his reasoning is not always free of controversy.

Examples

Examples of the relationship between ontogeny and phylogeny can be found in most multicellular animals as well - limited - even in plants:

• Some Urmünder ( Protostomia ) and new mouths ( deuterostomes ) form of a bubble nucleus ( blastula ), in the then einsenkt the primitive gut ( archenteron ). The resulting ( gastrula ) stage is anatomically similar to a hollow animal.
• Man, too, is the age of a few weeks after fertilization in the neck region of gill slits. Some critics are of the view that the interpretation of these untrained organs is inadmissible as " gills". But there is no coherent alternative interpretation for these structures that occur exactly where the gills would be expected.
• Even before the spine, the notochord is applied, as it is found in amphioxus.
• The fetus has the whole body on a hair, called lanugo.
• The human embryo has a tail spine that is nearly as large as that of a corresponding porcine embryo and is reduced later.
• Larvae of flatfish, such as plaice or flounder, have their eyes on each side of the body, as well as other fish. Only in the further development migrates an eye on the future top.

Interpretations and explanations

In addition to the classical recapitulation theory, as Haeckel has represented them, there is a weaker version that perches rule. This called rule of 1828, also called " law of corresponding stages ", the recapitulation theory was preceded by nearly 40 years. It says in essence, " The larvae or embryos of two different species resemble each other more strongly than adult specimens of the same species. "

So wrote von Baer then on vertebrate embryos: "I can not say to what class they belong absolutely. It may be lizards, small birds, or very young mammals, so complete is the similarity in the shape of the bodywork of the head and trunk in these animals. "

The biologist Gregory Bateson took up this idea in his book Mind and Nature again. Although there are obvious exceptions to this rule ( insect larvae, for example), yet they deliver an important key to the process of evolution. He generalized the statement to the formulation that " similarities precede the differences in time ". He also provided a explanation why this should be so: the evolutionary selection by a genetic mutation is conservative. A mutation that affects the embryonic stage is eliminated tends to grow faster than one mutation, which engages in the adult stage until later. " The change that takes effect earlier in the life of the embryo, a longer and more complex corresponding chain of subsequent events must interfere. "

More recently, the recapitulation theory is discussed again in connection with the discovered in the 1970s Hox genes. These genes are very old and complex genes that specify very general body structures and show up in the same form in animals of different species. These genes act as a fairly early stage in embryonic development. So writes the Berlin evolutionary biologist Carsten Niemitz: "It is impressive to see how those inconceivably old Gene implement their information in living form, as we humans would be something like amphioxus, which still have no head, or even simpler tiny marine animals. "

Criticism

Creationists and fundamental biogenetic law

In almost every creationist publication, the biogenetic law plays a significant role and finds more attention than in the scientific biology. The religiously motivated campaign against Ernst Haeckel (he was an avowed and eloquent free spirit ) and "to be" fundamental biogenetic law or the theory of evolution was first in 1909, according to following a lecture Haeckel for the fiftieth anniversary of the first publication of Charles Darwin's work The Origin of Species.

A covenant Kepler -called Christian organization accused Haeckel of having falsified some of his images embryos. In the daily press then raged a fierce battle for " Haeckel's embryos Pictures". Haeckel admitted that he had some pictures schematically what is common in science: " ... I will only start simultaneously with the rueful admission that a small part of my numerous embryos images ( maybe 6 or 8 of hundreds ) really (in the sense, forged by Dr. Braß ) ' are - namely all those in which the present observational material is so incomplete or insufficient that one is forced upon establishment of a coherent development chain, fill in the gaps by hypotheses ". Was finished in this campaign in a statement, signed numerous German biologists and anatomists. In it, although Haeckel accused the schematization as misconduct, but his interpretation accepted as correct. Here, researchers relied on more recent embryological studies that are far more accurate than the material used by Haeckel.

Both the federal government and the Kepler Monistenbund ( a free spiritual union that Haeckel declined ) published documentation about the campaign. The current dominance of creationist writings from the USA had this historical confrontation forgotten.

Scientific criticism

Substantive criticism

Already the botanist Carl Wilhelm von Naegeli (1817-1891) threw Haeckel equate the term ontogeny of embryonic development and the rising phase of individual development and at the same time exclude relevant phenomena such as the change of generations in plants. The notion is wrong in the individual development new stadiums would each be increased to a condensed and more or less disturbed recapitulation of phylogeny. Rather profoundly transformative changes of evolutionary significance can occur at any stage of ontogeny.

Even Stephen Jay Gould's Ontogeny and Phylogeny book is critical of the theory and tried to " exorcise the spirit Haeckel, so that evolutionary biology can be discussed without having to deal with that biogenetic law '." He further criticized Haeckel's reference to Lamarck and his theories. Haeckel saw, however, no irreconcilable contradiction in the theories of Goethe, Darwin and Lamarck (see Haeckel's works of creation and history General morphology).

Fraud allegations

→ Main article: Embryos Controversy

Michael Richardson of the St. George's Hospital Medical School in London in 1997 drew significant differences in embryos of marsupials, tree frogs, snakes and alligators, so that he could hardly imagine that Haeckel's drawings were real. He thinks they are cheating.

The geneticist and Nobel laureate Christiane Nüsslein -Volhard commented in an interview:

Historians of science refer out, however, that the drawings Haeckel's mostly shown in the discussion is based in large part on sketches of his predecessors (eg Baer 1828), without these, the forgery was accused (even details and the attitude of individual limbs are often identical ). Haeckel's descriptions represent therefore the perception at the beginning of the 19th century. Also presented Haeckel & Co., the embryos dissected, and had no yolk sac and appendages - usually described in the blurb to the panels, partially also in the text - while the photos used for comparison, these often.

The probably meant in the attacks at the beginning of the 20th century " schematic " illustrations can be found in Haeckel's History of Creation ( 1879 Berlin, between page 272 and 273).

Recapitulation in the evolutionary and developmental psychology

An attempt was made to transfer the recapitulation theory on the development of psychology and the cultural development of the people was. Thus, children have in the course of their socialization stages of cultural development of man. These approaches were long regarded as misguided, especially since they were exploited ideologically, to prove about that some cultures evolved in one, while others are in a "primitive" stage. However, recent research from the field of evolutionary psychology and cognitive archeology have at least point to parallels between the cognitive evolution of man and the cognitive development of children. This relates to cognitive performance and features such as language, music, symbolic thinking, and generally the interaction of cognitive modules.