(1899-1972) English zoologist who made important contributions to embryology and evolution. He disproved the germ-layer theory and developed the concept of pedomorphism (the retention of juvenile characteristics of ancestors in mature adults).
De Beer was born in London, studied at Oxford and lectured there. In 1945 he became professor of embryology at University College, London, then was director of the British Museum (Natural History) 1950–60.
In Introduction to Experimental Embryology 1926, De Beer observed that certain cartilage and bone cells are derived from the outer ectodermal layer of the embryo. This finally disproved the germ-layer theory, according to which these cells are formed from the mesoderm. Paedomorphism was first described in Embryos and Ancestors 1940, refuting the theory that the embryonic development of an organism repeats the adult stages of the organism’s evolutionary ancestors.
De Beer’s studies of the fossil Archeopteryx, the earliest known bird, led him to propose mosaic evolution —whereby evolutionary changes occur piecemeal—to explain the presence of both reptilian and avian features.