pageant of life's phylogeny on Earth—and such a claim for nontheoretical
independence of macroevolution generates no dispute, even between rigid
reductionists who grant no separate theoretical space to macroevolution, and
biologists, like myself, who envisage an important role for distinctive
macroevolutionary theory within an expanded and reformulated Darwinian view of
life.
In his description of the reductionist view of classical Darwinism—his own
opinion in positive support, not a simplistic caricature in opposition— Hoffman
(1989, p. 39) writes: "The neodarwinian paradigm therefore asserts that this history
of life at all levels—including and even beyond the level of speciation and species
extinction events, embracing all macroevolutionary phenomena—is fully
accounted for by the processes that operate within populations and species." I
dedicate my book to refuting this traditional claim, and to advocating a helpful role
for an independent set of macroevolutionary principles that expand, reformulate,
operate in harmony with, or (at most) work orthogonally as additions to, the
extrapolated, and persistently relevant (but not exclusive, or even dominant) forces
of Darwinian microevolution.
This perspective of synergy confutes the contrary, and ultimately destructive,
attempts by late 19th and early 20th century macroevolutionists to develop
substitute mechanisms that would disprove or trivialize Darwinism, and that spread
such a pall of suspicion over the important search for non-reductionistic and
expansive evolutionary theories—a most unfortunate (if historically
understandable) trend that stifled, for several generations, the unification and
fruitful expansion of evolutionary theory to all levels and temporal tiers of biology.
Thus, for example, my attempt to develop a specia-tional theory of macroevolution
(Chapters 8 and 9), with species treated as irreducible Darwinian individuals
playing causal roles analogous to those occupied by organisms in Darwinian
microevolution, represents an extension of Darwinian styles of explanation to
another hierarchical level of analysis (with interestingly different causal twists and
resulting patterns), not a refutation of natural selection from an alien realm. (Such a
speciational theory, however, does counter Hoffman's reductionistic claim of full
theoretical sufficiency for "processes that operate within populations and
species"—for, given the stasis of species under punctuated equilibrium, such
macroevolutionary patterns originate by higher-order sorting among stable species,
and not primarily by processes occurring anagenetically within the lifetime of these
higher-level Darwinian individuals.) Similarly, the different rules of catastrophic
mass extinctions require additions to the extrapolated Darwinian and
microevolutionary causes of phyletic patterns, but do not refute or deny the
relevance of conventional uniformitarian accretions through geological time. (In
fact, a more comprehensive theory that seeks to integrate the relative strengths, and
interestingly disparate effects, of such different levels and forms of continuationist
vs. catastrophic causality offers greater richness to Darwinian perspectives as both
underpinnings and important contributors to a larger totality.)
A second authorial input must arise from the distinctive ontogeny of past
56 THE STRUCTURE OF EVOLUTIONARY THEORY