Tiers of Time and Trials of Extrapolationism 1327
two controversial topics of the last quarter of the 20th century: punctuated
equilibrium and catastrophic mass extinction, our two most notorious hypotheses
about the non-homogeneity of time's principal modes.
In proposing that we conceptualize time as a rising set of tiers, I do not argue
(thus hoping to forestall, by this explicit statement, the same misunderstanding
kindled by the debate about hierarchical levels of selection) that entirely new, and
truly anti-Darwinian, forces emerge at each higher tier. I am quite content to allow
that no fundamental laws of nature, and any entirely novel causes or phenomena,
make their first appearance in larger slices of time. But, at these broader scales and
intervals, the known principles of genetics, and the documented mechanisms of
selection, may operate by distinct and emergent rules that, as a consequence of time's
tiering, cannot be fully predicted from the operation of the same kinds of causes at
lower levels. The logic of this critique flows from potential fallacies in Darwinian
assumptions about extrapolation across time's putative smoothness and causality's
supposed invariance. (Selection on species-individuals, for example, follows all the
abstract and general principles required by Darwinism for this central mechanism of
the general theory, but the modes and regularities of selection at this higher level
differ strongly, and cannot be predicted, from our canonical understanding of
Darwinian organismal selection within populations— see Chapter 8.)
The dilemma, and eventual insufficiency of the Modern Synthesis for
paleontology lay in this third crucial Darwinian claim that all theory could be
extrapolated from the first tier, thus converting macroevolution from a source of
theory into a pure phenomenology—a body of information to document and to render
consistent with a theoretical edifice derived elsewhere. But if the tiers of time, and
the hierarchy of life's structure, create pattern by emergent rules not predictable from
processes and activities at lower tiers, then paleontology will add insights, and
augment theory, without contradicting the principles of lower tiers.
We need to distinguish between the stability and continuity of causal principles
(the spatiotemporal invariance of natural law in our usual jargon) and the potentially
discontinuous (and disparate) expression of these principles across a spectrum of time
that may be strongly stepped (as nucleating points attract surrounding events, and as
nature's inherent structure clears out space at the unstable positions between), rather
than fully and smoothly continuous. I began my original article (Gould, 1985a, p. 2)
on the tiering of time with an admittedly humble analogy that may still help to clarify
the important principle of noncontradiction between structural tiering and a unitary
order of underlying entities and causes:
In the glory days of Victoria's reign, when a pound bought more than five
American dollars, the English economy operated on two distinct tiers. The
working man, paid weekly for his labor and without benefit of banking or
hope of accumulation, might pass his entire life without ever seeing a pound
note, for he received his wage in shillings and pence and