Editing Phylogenetics (section)

=== Ernst Haeckel's recapitulation theory ===

The modern concept of phylogenetics evolved primarily as a disproof of a previously widely accepted theory. During the late 19th century, [[Ernst Haeckel]]'s [[recapitulation theory]], or "biogenetic fundamental law", was widely popular.<ref>{{cite web| title=Early Evolution and Development: Ernst Haeckel| publisher=UC Museum of Paleontology| url=https://evolution.berkeley.edu/the-history-of-evolutionary-thought/1800s/early-evolution-and-development-ernst-haeckel/}}</ref> It was often expressed as "[[ontogeny]] recapitulates phylogeny", i.e. the development of a single organism during its lifetime, from germ to adult, successively mirrors the adult stages of successive ancestors of the species to which it belongs. But this theory has long been rejected.<ref>Blechschmidt, Erich (1977) ''The Beginnings of Human Life''. Springer-Verlag Inc., p. 32: "The so-called basic law of biogenetics is wrong. No buts or ifs can mitigate this fact. It is not even a tiny bit correct or correct in a different form, making it valid in a certain percentage. It is totally wrong."</ref><ref>Ehrlich, Paul; Richard Holm; Dennis Parnell (1963) ''The Process of Evolution''. New York: McGraw–Hill, p. 66: "Its shortcomings have been almost universally pointed out by modern authors, but the idea still has a prominent place in biological mythology. The resemblance of early vertebrate embryos is readily explained without resort to mysterious forces compelling each individual to reclimb its phylogenetic tree."</ref> Instead, [[Evolutionary developmental biology|ontogeny evolves]]&nbsp;– the phylogenetic history of a species cannot be read directly from its ontogeny, as Haeckel thought would be possible, but characters from ontogeny can be (and have been) used as data for phylogenetic analyses; the more closely related two species are, the more [[Cladistics#apomorphy|apomorphies]] their embryos share.