Biogenetic Law

Commonly summarized as “ontogeny recapitulates phylogeny” (on-TA-jeh-nee re-cah-PIT-you-lates fill-AH-jeh-nee), biogenetic law posits that the embryonic stages in the development of an individual (its ontogeny) repeat the evolutionary history of its ancestors (its phylogeny). A corollary of the biogenetic law is the idea that new evolutionary features are typically added at the end of development, with formerly adult, or “terminal” stages gradually being compressed into progressively earlier stages (or sometimes being eliminated outright).