Embryology and the Modern Synthesis in Evolutionary Theory

Abstract

Did embryology and, more specifically, experimental embryology assist in the creation of the modern synthesis during the thirties and early forties, or, on the contrary, was it a retarding element? The major works that embody the modern synthesis by Huxley (1942), Dobzhansky, Fisher, Haldane, Mayr, Simpson, and Wright hardly mention embryonic development. This omission is somewhat strange because Huxley was sufficiently interested in growth and development to write two books on this topic: one on relative growth (1932), and a text of experimental embryology with de Beer (1934). His book on evolution clearly shows the dominance of Huxley the naturalist over Huxley the embryologist. Obviously, the modern synthesis had a strong foundation in Mendelian and population genetics and its mathematical treatment, in ecology, and in field studies of speciation. It could well afford to dispense with embryology, although its implications for genetics and evolution were recognized by the founders of the modern synthesis. Conversely, the contemporary leading books on experimental embryology, by Schleip (1929), Spemann (1936), and Weiss (1939), did not include considerations of evolution. The modern synthesis did not receive assistance from contemporary embryologists.