1286 THE STRUCTURE OF EVOLUTIONARY THEORY
or inherent potentials, that, ever since Darwin's excellent arguments against Mivart,
have been recognized as the basis of quirky functional shift in unpredictable
evolutionary sequences remaining entirely under selectionist control); and the
extensive and influential set of material features that actually "stand and wait" by
themselves as nonadaptive attributes (not as additional but now only potential uses of
present adaptations). In other words, I choose this fundamentum because miltons (and
not franklins) pose a genuine challenge to the exclusivity of adaptationist
mechanisms. Franklins enlarge the scope and sophistication of selectionist argument,
adding a genuine flavor of formalist limitation and potentiation to an otherwise
naively functionalist theory based only upon organic accommodation to selective
pressures of an external environment. But miltons emplace a genuinely
nonadaptionist component into the heart of evolutionary explanation—for if many
features originate as nonadaptations, and if nonadaptations, as material items of
miltonic "stuff," stand and wait while occupying a substantial percentage of the
exaptive pool, then evolutionary explanations for both the origin of novelties, and for
the differential capacity of lineages to enjoy future phyletic expansion and success,
will require a revised and expanded version of Darwinism, enriched by
nonselectionist themes of a formalist and structuralist research program. I therefore
choose my fundamentum as the best taxonomic device for exploring the role of
nonadaptation and structural constraint in the exaptive pool of evolvability.
Cross-level effects as Miltonic spandrels, not Franklinian
potentials: the nub of integration and radical importance
As one of its most interesting and potentially reformatory implications, the
hierarchical expansion of selectionist theory introduces an extensive array of features
into the exaptive pool (and upon the consciousness of evolutionary biologists) as
effects propagated to other levels by features that arise for directly causal reasons at a
focal level. (One need not challenge the conventional view that most direct reasons at
focal levels will be selectionist and adaptational—for the propagated effects may still
assume a different and non-adaptive status.) What shall we call such effects that only
become manifest at other levels and may be truly invisible at the focal level of their
generation as consequences? Shall we interpret them as franklins, or inherent and
presently unexploited utilities of features originating for other functions—with their
only difference from more conventional franklins (flight capacities of
thermoregulatory feathers) resting upon the fact that they happen to reside in
biological individuals at levels other than the level of the feature that generated them?
I do not think that such cross-level effects can be interpreted as franklins, or
mere potentials. Rather, cross-level effects are available things, albeit available only
to biological individuals at other levels. Cross-level effects are therefore miltons, not
franklins. Franklins are potentials, not things. As such, franklins can only be recruited
sequentially in time from the primary adaptations in which they inhere as alternative
utilities (feathers for flight following