The Modern Synthesis as a Limited Consensus 587
belonged to the geologists, and students of fossils therefore received virtually no
training in evolution. With few exceptions, notably the work of G. G. Simpson,
paleontology (at least during the first half of the 20th century) played little role in
the development of a theory to account for its own subject matter.
Second, and more important in summarizing the first half of this book: not
only can we identify basic logical weaknesses in standard defenses for the three
Darwinian supports, but cogent critiques have also been persistent, indeed
omnipresent though changing in form, throughout the history of evolutionary
thought. These histories may not be widely known to current practitioners, but the
best minds of our profession have struggled continuously with themes of the
essential tripod—and their arguments deserve our attention and respect. (Without
this knowledge, we tend to imbue orthodoxies with false permanence or, even
worse, to lose sight of basic principles in the surrounding silence, thereby
converting dubious but central postulates into hidden assumptions. History can and
should be liberating.)
For the first leg of the tripod of essential support, hierarchy theory and
multiple levels of selection do not represent only a modern gloss upon Darwinism.
Rather, contemporary versions of these concepts have reinvigorated the oldest
issue of our profession. In Chapter 3, I showed that the first two evolutionary
systems well known to English-speaking naturalists—Lamarck's and Chambers's—
relied on a causal hierarchy that contrasted progress with diversification. Darwin
explicitly combatted these ideas with a single-level theory based on extrapolating
the small and observable results of natural selection, operating on organisms in
local populations, to render all evolutionary phenomena at all scales of time and
effect. Weismann, and Darwin himself as he struggled to explain diversity, then
considered hierarchical models of selection formulated very much in the spirit of
modern versions. Weismann, after much internal debate, leading to eventual
rejection of his previous commitment to the strict Darwinism of single-level
selection on organisms alone, eventually advocated a full hierarchy of levels,
explicitly citing this concept as the most distinctive innovation and centerpiece of
his mature evolutionary views.
The internalist critique of adaptationism (the main subject of modern criticism
on the second, or "creativity," leg of the tripod) boasts an even more venerable
pedigree. I showed, in Chapters 4 and 5, how this critique defined the major
difference between British (Paleyan) and continental versions of natural theology
in preevolutionary days. I then demonstrated that the same division, transformed as
the structuralist-functionalist dichotomy, served as a focus for evolutionary
debate—pitting the functionalism (adaptationism) of such disparate theories as
Darwinian selectionism and Lamarckian soft inheritance against the great
continental schools of structuralism, as advocated by such scientists as Goethe (and
most of the German Naturphilosophen), Geoffroy Saint-Hilaire (and the French
transcendental morphologists), and, in a rare move across the Channel, in major
themes of the complex and much misunderstood evolutionary views of Richard
Owen. Finally, I traced the two