830 THE STRUCTURE OF EVOLUTIONARY THEORY
are significantly different from each other; most characters return to their original
states."
This complex anatomy of stasis again illustrates an active process of main-
tenance. Perhaps Futuyma's insight (see pp. 796-802) about linkage between
speciation and achieved, stable morphological change can also help in this case. I
suspect that much of the fluctuation, especially the occasional abrupt changes,
represents a complex mosaic of shifting geographic borders for transient local
populations. Vertical sequences probably record a mixture of temporary change
within local populations and successive migrations of distinct local populations in
and out over the same geographic spot (sample pit in this case). But both of these
sources—short-term changes within a population and the mosaic of differences
between demes—will be transient and fluctuating unless a set of differentia can be
"locked up" by reproductive isolation within a newly formed species. Since Bell's
sequence includes no events of speciation, sustained changes do not accrue. The
unusual extent of directionless fluctuation then records the especially high degree
of temporal resolution.
Bell and colleagues (1985, p. 258) conclude correctly "the irregular patterns
and great magnitude of phenotypic changes that are observed indicate that
conventional paleontological samples may miss important evolutionary phenomena
and are not comparable to shorter-term evolution in extant populations." Fair
enough; I asserted the same argument earlier (see p. 801) by metaphorical
comparison to our current cliché for illustrating different scales of fractal self-
similarity: one cannot measure around every headland of every sea-cove (transient
changes over years in local populations) when calculating the coastline of Maine
(macroevolutionary trends over millions of years) at the scale of a single page in an
atlas. But one must firmly reject the tempting implication that either scale can be
judged "better" or more complete. Yes, the paleontological scale misses "important
evolutionary phenomena" of transient fluctuation in local populations. But
measurement of details at this local scale cannot be extrapolated to encompass or
explain a macroevolutionary trend either—and such local details therefore miss
"important evolutionary phenomena" as well. Rather than accusing any level of
insufficiency for its inevitable inability to resolve events at other unrecorded
scales, we should simply acknowledge that any full understanding of evolution
requires direct study and integration of the fascinating uniquenesses (as well as the
common features) of all hierarchical levels in time and structure.
I have emphasized that one cannot achieve a proper "feel" for the relative
frequency of punctuated equilibrium merely by tabulating published cases for
individual lineages (whereas the study of relative frequency in a well-bounded,
taxon, time, or environment—provided that researchers do not preselect their
circumstances based on well-documented subjective appearance in favor of one
side or the other—has yielded valuable data, as discussed on pp. 854-874). Claims
for gradualism attain their highest frequencies at "opposite" ends of the
conventional chain of being—that is, for foraminifers and for mammals. In my
partisan way, I suspect that the former case may be valid, but attributable to
biological differences that predict gradualism within