Recapitulation theory

"Ontogeny recapitulates phylogeny", also called the "biogenetic law" or the "theory of recapitulation", is a now discredited hypothesis in biology first espoused in 1866 by Ernst Haeckel. Ontogeny refers to the development of the embryos of a given species; phylogeny refers to the evolutionary history of a species. The theory claims that the development of the embryo of every species repeats the evolutionary development of that species.

In order to support his theory, Haeckel produced several fraudulent embryo drawings which overemphasized similarities between embryos of related species and found their way into many biology textbooks.

Modern biology rejects Haeckel's theory. While for instance the phylogeny of humans as having evolved from fish through reptiles to mammals is generally accepted, no cleanly defined "fish", "reptile" and "mammal" stages of human embryonal development can be discerned.

The fact that the strict recapitulation theory is rejected by modern biologists has sometimes been used as an argument against evolution by creationists. The argument is: "Haeckel's theory was presented as supporting evidence for evolution, Haeckel's theory is wrong, therefore evolution has less support". This argument is not only an oversimplification but misleading because modern biology does recognize numerous connections between ontogeny and phylogeny, explains them using evolutionary theory without recourse to Haeckel's specific views, and considers them as supporting evidence for that theory. See: ontogeny and phylogeny.

Historical impact

Although Haeckel's specific form of recapitulation theory is now discredited among biologists, it did have a strong impact in social and educational theories of the late 19th century. The maturationist theory of G. Stanley Hall[?] was based on the premise that growing children would recapitulate evolutionary stages of development as they grew up and that there was a one to one correspondence between childhood stages and evolutionary history, and that it was counterproductive to push a child ahead of its development stage.

External links

• Haeckel, E. 1899. Riddle of the Universe at the Close of the Nineteenth Century. Cited at http://www.ucmp.berkeley.edu/history/haeckel.
• Division of Biology and Medicine, Brown University, Evolution and Development I: Size and shape, http://biomed.brown.edu/Courses/BIO48/30.S&S.HTML
• Rebecca Irwin, Ontogeny and Phylogeny, http://www.utm.edu/~rirwin/391OntogPhylog.htm
• Stephen S. Gould, Ontogeny and Phylogeny, Cambridge Mass.: Belknap Press of Harvard University Press, 1977