Historical Constraints and the Evolution of Development 1083
Osborn, the patrician "kingmaker" of American paleontology (and quite a
potentate in American science in general), cited Scott's definitions in several papers,
paying special attention—in the context of his own pluralistic views on the
importance of both formal and functional factors as evolutionary causes—to the role
of parallelism in combining the push of selection (or some other functionalist cause)
with the internal channeling of constraint as the architect of preferred pathways for
any agent of "pushing." For example, in his 1902 paper on "Homoplasy as a law of
latent or potential homology," Osborn had already identified parallelism as falling
into a gray zone between the pure analogy of convergence and the pure homology of
unaltered inheritance. With parallelism's notion of "predeterminate variation" (1902,
p. 270), Osborn argues, "I think we have to deal with homology or, more strictly,
with a principle intermediate between homology and analogy."
In a 1905 article on "The ideas and terms of modern philosophical anatomy,"
Osborn then presented a first chart (reproduced here as Fig. 10-13) of relations
among these terms, including parallelism and convergence as sub-categories of
analogous resemblance (in contrast with homologous resemblance here restricted to
Lankester's notion of homogeny). His chart depicts the geometrical distinction
between parallelism and convergence, but his definitions follow Scott in relying not
on the descriptive difference between parallel and converging lines, but on "similar
characters arising independently in similar or related animals or organs" for
parallelism, vs. "similar adaptations arising independently in dissimilar or unrelated
animals or organs" for convergence.
These foundational statements indicate both the conceptual clarity and the