firm outlines—for the revised structure of evolutionary explanation remains a work
vigorously in progress, as only befits the nature of its subject, after all!—of a far
richer and fascinatingly different theory with a retained Darwinian core rooted in
the principles of natural selection. In short, we live in the midst of a Falconerian
remodeling of our growing and multiform, yet coherently grounded, intellectual
mansion.
I will not, in this chapter, detail the nature of the K-cuts that failed (thus
preserving the central logic of Darwinism), the R-cuts that have succeeded in
changing the structure of evolutionary theory in such interesting ways, and the
S-cuts that have refurbished major rooms in particular wings of the edifice—for
these specifications set the subject matter of all following chapters. But to provide
a better opening sense of this book's argument—and to clarify the nature of the
three central claims of Darwinian logic—I shall at least distinguish, for each
branch, the K-cuts that never prevailed (and therefore did not fell the structure)
from the R-cuts that have affected each branch, and have therefore provoked our
current process of building an enriched structure for evolutionary theory.
Returning to Scilla's coral (Fig. 1-4), consider the central branch as the first
leg of the tripod (agency, or the claim for organismal selection as the causal locus
of the basic mechanism), the left branch as the second leg (efficacy, or the claim
that selection acts as the primary creative force in building evolutionary novelties),
and the right branch as the third leg (scope, or the claim that these
microevolutionary modes and processes can, by extrapolation through the vastness
of geological time, explain the full panoply of life's changes in form and diversity).
The cut labeled Kl on Figure 1-4 would have severed the entire coral by
disproving natural selection as an evolutionary force at all. The cut labeled K2
would have fully severed the second branch, leaving natural selection as a
legitimate cause, but denying it any creative role, and thereby dethroning
Darwinism as a major principle in explaining life's history. (We shall see, in
Chapters 3-6, that such a denial of creativity underlay the most common anti-
Darwinian argument in the first generations of debate.) The cut labeled КЗ would
have fully severed the third branch, allowing that natural selection might craft
some minor changes legitimately called "creative" in a local sense, but denying
that Darwin's mechanism could then be extended to explain the panoply of
macroevolutionary processes, or the actual pageant of life's history. The success of
any one of these K-cuts would have destroyed Darwinian theory, plain and simple.
None of them succeeded, and the foundation of Darwinian central logic remains
intact and strong.
In striking, and most positive, contrast, I believe that higher R-cuts—leaving
the base of each major branch intact, but requiring a substantial regrowth and
regrafting of an enlarged structure upon the retained foundation—have been
successfully wielded against all three branches of Darwinian logic, as the structure
of evolutionary theory developed in the last third of the 20th century (following too
rigid a calcification of the original structure, a good adumbration of the coral
metaphor!, in the hardening of the Modern Synthesis
Defining and Revising the Structure of Evolutionary Theory 21