Strickland and Wallace, and the systematic argument for evolution

Although the history of evolutionary thought in the Nineteenth Century has been studied extensively, the conceptual development of systematics during that period has been comparatively neglected. Hugh Edwin Strickland (1811–1853), reacting against the quinarian systematists of the 1830’s, developed an approach to systematics in 1841 (Ann. Mag. Nat. Hist., 6: 184–194) that rejected previous notions of the symmetry and two-dimensionality of taxonomic relationships, and argued that relationships of analogy have no place in the natural system. (The quinarians had argued that both affinity and analogy were important in systematics.) Strickland illustrated the results of his approach with systematic “maps” which diagrammed the relationships of taxa. Alfred Russel Wallace (1823–1913) explicitly adopted Strickland’s approach in 1856 (Ann. Mag. Nat. Hist., ser. 2, 18: 193–216), but made subtle changes, including the removal of extant taxa from map nodes, that permitted the diagrams to be given an evolutionary interpretation. Wallace’s systematic work, particularly his advocacy of Strickland’s map-making approach, was a central part of the evolutionary argument he was building in the 1850’s, and was at least as important as this often-cited 1855 work in biogeography.