- Hierarchical models of evolutionary processes (at least descriptively so, but
causally as well) have been featured and defended by evolutionary theorists from
the beginning of our science, although not always by good or valid arguments. This
inadequately recognized theme explains the major contrast between Lamarck and
Darwin, and coordinates the various disputes between Wallace and Darwin.
Wallace simply didn't grasp the concept of levels at all, and remained so
committed to adaptationism that he ranged up and down the hierarchy, oblivious of
the conceptual problems thus entailed, until he found a level to justify his
adaptationist bent. Darwin, by contrast, completely understood the problem of
levels, and the reasons behind his strong preference for a reductionist and single-
level theory of organismal agency— although he reluctantly admitted a need for
species selection to resolve the problem of divergence. We can also understand
why Wallace's 1858 Ternate paper, sent to Darwin and precipitating the "delicate
arrangement," did not proceed as far to a resolution as later tradition holds, when
we recognize Wallace's conceptual confusion about levels of selection.
Chapter 4: Intemalism and laws of form: pre-darwinian alternatives- In a brilliant closing section to his general chapter 6, entitled "difficulties
on theory," Darwin summarized the logical structure of the most important
challenge to his system, and organized his most cogent defense for his functionalist
theory of selection, by explicating the classical dichotomy between "unity of type"
and "conditions of existence"—or the formalism of Geoffroy vs. the functionalism
of Cuvier—entirely in selectionist terms, and to his advantage. He attributed
"conditions of existence" to immediate adaptation by natural selection, and then
explicated "unity of type" as constraints of inheritance of homologous structures,
originally evolved as adaptations in a distant ancestor. Thus, he identified natural
selection as the underlying "higher law" for explaining all morphology as present
adaptation or as constraint based on past adaptation. He also admitted, while
cleverly restricting their range and frequency, a few other factors and forces in
evolutionary explanation. - A fascinating, and previously unexplored, contrast may be drawn between
the strikingly similar dichotomy, although rooted in creationist explanations, of
Paley's functionalist and adaptationist theory of divine construction for
individualized biomechanical optimality vs. Agassiz's formalist theory of divine
ordination of taxonomic structure as an incarnation of God's thoughts according to
"laws of form" reflecting modes and categories of eternal thought. Clearly, this
ancient (and still continuing) contrast between structural and functional
conceptions of morphology transcends and predates any particular mechanism,
even the supposedly primary contrast of creation vs. evolution, proposed to explain
the actual construction of organic diversity. - In the late 18th century, the great poet (and naturalist) Goethe developed a
fascinating (and, in the light of modern discoveries in evo-devo, more than partly
correct) archetypal theory in the structuralist or formalist mode— and explicitly
critical of functionalist, teleological and adaptationist alterna-
Defining and Revising the Structure of Evolutionary Theory 65