Embryological Archetypes and Homology: Establishing Evolutionary Embryology

Abstract

Embryology increasingly came to be viewed as the way to understand relationships among different groups of organisms. As discussed in the first section of this chapter, Von Baer played a pivotal role in this development. His ideas were rapidly assimilated into Britain as scientists there responded to the implications of the Geoffroy-Cuvier debate (s. 5.2). Richard Owen made a lasting impact when he separated homology from analogy (s. 5.3), and Darwin took account of these developments in formulating his theory (s. 5.4). The search for embryological archetypes and establishment of an evolutionary embryology was carried furthest by Ernst Haeckel in Germany and Francis Balfour in England. By the late 19th century a solution to the generation of organismic form appeared to be at hand in homologous germ layers and conserved stages of embryonic development. This evolutionary embryology was applied to relationships among organisms and in a search for the ancestors of the vertebrates (s. 5.5).

‘Homologue … The same organ in different animals under every variety of form and function. Analogue … A part or organ in one animal which has the same function as another part or organ in a different animal.’ Owen, 1843, pp. 374, 379