The Essence of Darwinism and the Basis of Modern Orthodoxy 167
We should use this perspective of engagement with the core commitments to
assess the relative theoretical importance of issues now commanding attention
among evolutionists. For example, Kimura's theory of neutralism (1983) ranks as
fundamental and reformative for proposing a new domain of causation at high
relative frequency. I regard as unfair, and disrespectful of Darwin's clear
commitments, the common rhetorical strategy of arguing, as Stebbins and Ayala
did for example (1981), that selection and neutralism should be judged as
competing paradigms comfortably embraced within the Modern Synthesis. The
Synthesis, as an intellectual structure, has always been understood as Darwinism
strengthened by modern knowledge about genetics and heredity. The Synthesis
must therefore assert a dominant relative frequency for selection. Of course such a
theory allows for neutrality—one could scarcely deny either the mathematics or the
conditions of potential operation—but only at a low relative frequency, so that the
preeminence of selection will remain unchallenged.
Kimura's claim for high, even dominant, relative frequency of neutral change
at the nucleotide level introduces a world different from Darwin's. At most, one
can say that this world, largely invisible at the organismic level, does not subvert
Darwin's proposal that selection dominates the phenotypic realm of overt form,
function, and physiology of organisms. But in so saying, we must admit that a
large part of reality, though unaddressed by Darwin himself, cannot be explained
on Darwinian principles if Kimura's theory holds. Darwinism does not fall thereby,
but a new and distinct domain, primarily regulated by a different style of causality,
has been added to evolutionary explanation. How can one deny that evolutionary
theory becomes substantially reformulated and enriched thereby? Why would one
want to issue such a denial, unless psychic health depends upon the continued
assertion of comfortable orthodoxy, whatever the required twist of logic?
My own expertise lies in paleontology, and this book shall emphasize
critiques from the attendant domain of macroevolution, descriptively defined as
patterns and causes of evolution at and above the species level. (I acknowledge, of
course, the fascination and transforming power of work at the molecular level. I
also recognize that macroevolution must shake hands with molecular genetics in
order to forge the new consensus. If this book slights the molecular side, my own
ignorance stands as the only cause, and this work necessarily suffers thereby.)
Basically, I shall defend the view that each leg of Darwin's essential tripod, as
explicated in this chapter, now faces a serious critique from the domain of
macroevolutionary change. These critiques rank as auxiliaries to Darwinism in
Kellogg's sense; for they either expand or add to the core commitments. But the
expansions are large and the additions substantial—so the resulting revision can no
longer be called ordinary Darwinism in any conventional meaning. I am convinced
that the three critiques intertwine in a potentially unified way. But consensus is
premature and we can only see the resulting shape of the revised and unified theory
through a glass darkly—though in the future, no doubt, face to face.