biogenetic law

biogenetic law in biology, a law stating that the earlier stages of embryos of species advanced in the evolutionary process, such as humans, resemble the embryos of ancestral species, such as fish. The law refers only to embryonic development and not to adult stages; as development proceeds, the embryos of different species become more and more dissimilar. An early form of the law was devised by the 19th-century Estonian zoologist K. E. von Baer, who observed that embryos resemble the embryos, but not the adults, of other species. A later, but incorrect, theory of the 19th-century German zoologist Ernst Heinrich Haeckel states that the embryonic development (ontogeny) of an animal recapitulates the evolutionary development of the animal's ancestors (phylogeny).

biogenetic law (recapitulation theory) Principle that the stages of embryonic development reflect the stages of an organism's evolutionary development. See also evolution

biogenetic law Law formulated by the embryologist E. K. von Baer (1792–1876) stating that the early stages of development in animal species resemble one another, the species diverging more and more as development proceeds.