888 THE STRUCTURE OF EVOLUTIONARY THEORY
because the Darwinian agent that we understand best, and that we have previously
deemed exclusive—the organism—happens to resist these modes of change as an
active consequence of its inherent structure. But nature builds her scales with
strong allometry, and not in a fractal manner with every higher level formed as an
isometrically enlarged version of each lower level enfolded within (Gould and
Lloyd, 1999).
I suggest that we challenge this idol of our traditional Darwinian
conceptualizations, and at least open ourselves to the opposite view that the
species-individual's capacity for change by drive and drift, as well as by selection,
defines a potential source of strength for this hierarchical level as an exploiter of
the full panoply of available causes for trends. Perhaps we should pity the poor
organism for its self-imposed restrictions. Or perhaps, rather, we should praise the
organism for managing to achieve so much with such a limited range of
mechanisms! (Pardon my metaphorical lapses. I am, of course, suggesting that we
view the different interplay of potential forces at various hierarchical levels as
sources of distinctiveness and strength for each. We will gain a better
understanding of evolutionary mechanics when we try to identify the particular
capabilities of each level rather than attempting to establish a single "gatekeeper's"
criterion for ranking levels in linear order by their quantity of a single enabling
power analogous to such fictions as IQ.)
In any case, this allometric expansion of potential mechanisms for trending at
the species level offers significant promise for fracturing by redefinition (rather
than solving in conventional terms) one of the great conundrums of paleontology—
an issue much fretted over, and bruited about, but usually (and finally) cast aside
with vague statements of hopeful confidence that traditional explanations will
suffice once we finally record enough details in any given case. At least in terms of
dedicated pages in our professional literature, trends represent the cardinal
subject of macroevolution (with differential waxing and waning of diversity within
and among clades, especially as influenced by episodes of mass extinction, as the
second great theme of evolutionary discussion in paleontology).
Paleontology has long been trapped in the dilemma of recognizing only one
conventional model for the explanation of trends, and then finding little credible
One might argue that this focus only records another of Bacon's idols rather than an
evident empirical reality. Bacon's idola tribus, or idols of the tribe, refer to mental biases
deeply rooted in inherent modes of mental functioning, or human nature itself. Humans are
pattern-seeking and story-telling creatures—and we prefer to tell our stories in certain modes
that may reflect particular cultural traditions as well as universal preferences of thought. We
shun randomness and non-directionality in favor of stories about movement in particular
directions for definable reasons subject to moral judgment. We compiled the entire Bible as a
grand and extended narrative in this mode, and then granted just one uncomfortable chapter
to Ecclesiastes as the loyal opposition, where "time and chance happeneth to all" and "there
is no new thing under the sun." Thus, our chosen focus upon trends in the paleontological
record may only record their salience in piquing our interests and preferences—and not a
genuinely high relative frequency among all clades in nature. This subject deserves a great
deal of thought and extended study. A remarkable article by Budd and Coates, 1992, on the
predominance of non-trending in the evolution of montastraeid corals may point the way to
substantial reform—see p. 937.