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de Beer, Sir Gavin Rylands

theory layer embryology adult

[duh beer ] (1899–1972) British zoologist: refuted germ-layer theory in embryology, and theory of phylogenetic recapitulation.

De Beer served in both world wars, in Normandy in 1944 with the Grenadier Guards as a Lieutenant-Colonel; in the interval he graduated from Oxford and he afterwards taught there. After the Second World War he became professor of embryology in London and from 1950 director of the British Museum (Natural History) until he retired in 1960. In 1926 he much injured the germ-layer theory in embryology by showing that some bone cells develop from the outer (ectodermal) layer of the embryo (the theory had them form from the mesoderm). In 1940 he also refuted E Haeckel’s (1834–1919) theory of phylogenetic recapitulation; according to this theory an organism in its embryonic stage repeats the adult stages of the organism’s evolutionary ancestors. De Beer showed that in fact the situation is rather the converse; adult animals retain some juvenile features of their ancestors (paedomorphism). His many other researches included studies of the earliest known bird, Archaeopteryx , and led him to propose a pattern of ‘piecemeal’ evolution to explain its possession of both reptilian and avian features (eg teeth and wings); he worked on the origin of the Etruscans from blood group data and on Hannibal’s route over the Alps.

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