The Essence of Darwinism and the Basis of Modern Orthodoxy 159
But suppose these precepts do not govern a commanding relative frequency of
cases? What if adaptation does not always record the primacy of natural selection,
but often arises as secondary fine tuning of structures arising in other ways? What
if variation imposes strong constraints and supplies powerful channels of preferred
direction for change? What if the nature of variation (particularly as expressed in
development) often produces change without insensible intermediacy?
All these arguments merge into a structuralist critique that seriously
challenges the predominant functionalism of classical Darwinism. As a common
thread, these challenges deny exclusivity to natural selection as the agent of
creativity, and claim a high relative frequency of control by internal factors.
McCosh was right in establishing his pre-evolutionary contrast of a "principle of
order" and a "principle of special adaptation" (see p. 116). Darwin was right in
translating this distinction into evolutionary terms as "Unity of Type" and
"Conditions of Existence," though he was probably wrong in his fateful decision—
the basis of Darwinian functionalism—to yoke the two categories together under a
common cause by defining unity of type as the historical legacy of previous
adaptation, thus asserting the domination of natural selection (1859, p. 206—see
extensive commentary in chapter 4). And E. S. Russell (1916) was also right in
contrasting the "formal or transcendental" with the "functional or synthetic"
approach to morphology.
We are children of Darwin, and an English school of adaptation and
functionalism far older than evolutionary theory. Darwin's key claim for the
creativity of natural selection—and the resulting sequelae of gradualism,
adaptationism, and the isotropy of variation—builds the main line of defense for
this powerful and venerable attitude towards nature and change. For many of us,
these claims lie too close to the core of our deeply assimilated and now largely
unconscious beliefs to be challenged, or even overtly recognized as something
potentially disputable. Yet a coherent alternative has been proposed, and now
provides one of the three most trenchant modern critiques of strict Darwinism. I
believe that these critiques, taken together, will reorient evolutionary theory into a
richer structure with a Darwinian core. But we cannot appreciate the alternatives
until we grasp the basis of orthodoxy as an argument of compelling brilliance and
power. Important critiques can only operate against great orthodoxies.
Environment as Enabler of Change The Third Theme: The Uniformitarian Need to Extrapolate:
EXTRAPOLATE; ENVIRONMENT AS ENABLER OF CHANGE
The first two themes—causal focus on organisms as agents of selection and
creativity of selection in crafting adaptation—establish the biological core of
Darwinian theory. That is, they perform the biological "work" needed to assure the
third and last essential component of a Darwinian worldview: the uniformitarian
argument for full application in extrapolation to all scales and times in the history
of life. Mere operation in the microevolutionary here and now cannot suffice.
Natural selection must also assert a vigorous claim for