The theory of recapitulation, also called the biogenetic law or embryological parallelism - and often expressed as "ontogeny recapitulates phylogeny" - is a hypothesis that in developing from embryo to adult, animals go through stages resembling or representing successive stages in the evolution of their remote ancestors. With different formulations, such ideas have been applied to several fields, including biology, anthropology and education theory. In biology, there are several examples of embryonic stages showing features of ancestral organisms, but a "strong" formulation of the concept has been discredited.
The concept originated in the 1790s among the German Natural philosophers and, as proposed by Étienne Serres in 1824–26, became known as the "Meckel-Serres Law". In 1866, the German zoologist Ernst Haeckel proposed that the embryonic development of an individual organism (its ontogeny) followed the same path as the evolutionary history of its species (its phylogeny).
The general agreement among historians is that the concept originated in the 1790s among the German Natural philosophers. The first formal formulation was proposed by Étienne Serres in 1824–26 as what became known as the "Meckel-Serres Law", it attempted to provide a link between comparative embryology and a "pattern of unification" in the organic world. It was supported by Étienne Geoffroy Saint-Hilaire and became a prominent part of his ideas which suggested that past transformations of life could have had environmental causes working on the embryo, rather than on the adult as in Lamarckism. These naturalistic ideas led to disagreements with Georges Cuvier. It was widely supported in the Edinburgh and London schools of higher anatomy around 1830, notably by Robert Edmond Grant, but was opposed by Karl Ernst von Baer's ideas of divergence, and attacked by Richard Owen in the 1830s.
Haeckel attempted to synthesise the ideas of Lamarckism and Goethe's Naturphilosophie with Charles Darwin's concepts. While often seen as rejecting Darwin's theory of branching evolution for a more linear Lamarckian "biogenic law" of progressive evolution, this is not accurate: Haeckel used the Lamarckian picture to describe the ontogenic and phylogenic history of the individual species, but agreed with Darwin about the branching nature of all species from one, or a few, original ancestors. Since around the start of the twentieth century, Haeckel's "biogenic law" has been refuted on many fronts.
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