The Essence of Darwinism and the Basis of Modern Orthodoxy 161
eventually absorbed the term. Darwin understood this etymological point perfectly
well, and he initially declined to use the word "evolution"—preferring "descent
with modification"—probably because he recognized the difference between the
literal meaning of "evolution" and his own concept of life's history and change by
natural selection—see Gould, 2000a.)
Darwin's theory, in strong and revolutionary contrast, presents a first
"externalist" account of evolution, in which contingent change (the summation of
unpredictable local adaptations rather than a deterministic unfolding of inherent
potential under internal, biological principles) proceeds by an interaction between
organic raw material (undirected variation) and environmental guidance (natural
selection). Darwin overturned all previous traditions by thus granting the external
environment a causal and controlling role in the direction of evolutionary change
(with "environment" construed as the ensemble of biotic and abiotic factors of
course, but still external to the organism, however intrinsically locked to, and even
largely defined by, the presence of the organism itself). Thus, and finally, in
considering the validity of extrapolation to complete the roster of essential
Darwinian claims, the role of the geological stage becomes an appropriate focus as
a surrogate for more overtly biological discussion.
If the uniqueness of Darwinism, and its revolutionary character as well,
inheres largely in the formulation of natural selection as a theory of interaction
between biological insides and environmental outsides—and not as a theory of
evolutio, or intrinsic unfolding—then "outsides" must receive explicit discussion as
well, a need best fulfilled within this treatment of extrapolation. Under internalist
theories of evolution, environment, at most, holds power to derail the process by
not behaving properly—drying up, as on Mars, or freezing over, as nearly occurred
on Earth more than once during our planet's geological history. Under Darwinian
functionalism, however, environment becomes an active partner in both the modes
and directions of evolutionary change.
As the Utopian tradition recognizes, we can often devise lovely and optimal
systems in abstract principle, but then be utterly unable to apply them in practice
because an imperfect world precludes their operation. The central logic of
Darwinism faces an issue of this kind. The two essential biological postulates of
natural selection—its operation at the organismal level, and its creativity in
crafting adaptations—build a sufficient theoretical apparatus to fuel the system.
The play of evolution can run with such a minimal cast, but we do not know
whether the drama can actually unfold on our planet until we also examine and
specify the character of the theater—the geological and environmental stage for the
play of natural selection. The geological stage therefore becomes a major actor in
the drama set on its own premises.
Moreover, and reinforcing my argument that Darwin's strength lies in his
brave specificity, Darwin places a great burden on geology and environment by
devising such stringent conditions for the nature of this external setting. Again, we
encounter the Goldilocks problem—environment cannot impose too much or
provide too little, but must be "just right" in the middle.
Environment, as an active Darwinian agent, cannot under perform. In particular,