Defining and Revising the Structure of Evolutionary Theory 85
tures, and even D'Arcy Thompson admitted that his mechanism could not
encompass, say, "hipponess," but, at most, only the smooth transformations of
these basic designs among closely related forms of similar Bauplan (the true
theoretical significance of his much misunderstood theory of transformed
coordinates). In summary, D'Arcy Thompson, the great student of Aristotle, erred
in mixing the master's modes of causality—by assuming that the adaptive value (or
final cause) of well designed morphology could specify the physical forces (or
efficient causes) that actually built the structures.
- Stuart Kauffman and Brian Goodwin have presented the most cogent
modern arguments in this tradition of direct physical causation. These arguments
hold substantial power for explaining some features of relatively simple biological
systems, say from life's beginnings to the origin of prokaryotic cells, where basic
organic chemistry and the physics of self-organizing systems can play out their
timeless and general rules. Such models also have substantial utility in describing
very broad features of the ecology and energy dynamics of living systems in
general terms that transcend any particular taxonomic composition. But this
approach founders, as did D'Arcy Thompson's as well, when the contingent and
phyletically bound histories of particular complex lineages fall under scrutiny—
and such systems do constitute the "bread and butter" of macroevolution.
Nonetheless, Kauffman's powerful notion of "order for free," or adaptive
configurations that emerge from the ahistoric (even abiological) nature of systems,
and need not be explained by particular invocations of some functional force like
natural selection, should give us pause before we speculate about Darwinian causes
only from evidence of functionality. This "order for free" aids, and does not
confute, such functional forces as selection by providing easier (even automatic)
pathways towards a common desideratum of adaptive biological systems. - I then turn to the second, and (in my judgment) far more important, theme
of structural constraint in the fully historicist and phyletic context of aptive
evolution by cooptation of structures already present for other reasons (often
nonadaptive in their origin), rather than by direct adaptation for current function
via natural selection. The central principle of a fundamental logical difference
between reasons for historical origin and current functional utility—a vital
component in all historical analysis, as clearly recognized but insufficiently
emphasized by Darwin, and then unfortunately underplayed or forgotten by later
acolytes—was brilliantly identified and dissected by Friedrich Nietzsche in his
Genealogy of Morals, where he contrasted the origin of punishment in a primal
will to power, with the (often very different) utility of punishment in our current
social and political systems. - Darwin himself invoked this principle of disconnection between historical
origin and current utility both in the Origin's first edition, and particularly in later
responses to St. George Mivart's critique (the basis for the only chapter that
Darwin added to later editions of the Origin) on the supposed inability of natural
selection to explain the incipient (and apparently useless) stages of adaptive
structures. Darwin asserted the principle of functional shift to argue that, although
incipient stages could not have functioned in the manner