1328 THE STRUCTURE OF EVOLUTIONARY THEORY
its total never reached a full pound. Meanwhile, bankers in the City of London
transacted the world's imperial business in pounds. India today operates on
two similar and largely noninteracting tiers—the 100-rupee notes (about ten
dollars) of the hotel shops and the bustling economy of the bazaars, where 10
rupees buy at least one of anything and no one ever sees (or could cash) a 100-
rupee note.
Our world of times and amounts is not always continuous. Its metrics
usually extend smoothly from one end to the other (shillings did grade to
pounds and rupees are rupees), but its activities are often sharply concentrated
in definite regions of a potential spectrum, with large open spaces between.
Systems often drive in opposite directions away from break points; location
on one or another side of a threshold inevitably pushes toward an equilibrium
far above or below.I do not know if we should make a formal attempt to specify a definite number
of tiers in time—as the principle seems sound, whereas definite criteria for precise
designation seem elusive. (I remain far more comfortable and confident with the
concept of hierarchy in levels of selection than with the increasing scale of tiers in
time—for the genealogical hierarchy can be elucidated with fair precision by criteria
of Darwinian individuality (see Chapter 8), whereas time's tiers lack such a unitary
concept for coordination. For the same reason, I do not follow my closest colleague
Niles Eldredge's attempt to identify dual or parallel hierarchies of genealogy and
ecology, for the genealogical units enjoy clear definition, whereas ecological levels,
like time's tiers, lack a coherent fundamentum divisionis for unambiguous
specification.)
But if I may make an analogy to the geological time scale for the Phanerozoic
eon, we may at least be confident about the few broadest tiers (the three geological
eras in my analogy), even while we argue about some boundaries and specifications
for the smaller units within these broad domains (geological periods in my analogy).
Darwinian organismal selection, with an overall statistical edge granted to biotic
competition in crowded ecosystems, dominates the first tier of anagenesis within
populations during ecological time. If the fractal principle of Darwin's central belief
in extrapolation held, then the norms of this process at the first tier would accumulate
in a linear fashion through time to yield a history of life with the same basic form and
causal structure, but scaled up in smooth continuity to generate all patterns of
phylogeny. I have designated life's failure to display this pattern, particularly its
disinclination to feature a clear signal of overall progress, as the "paradox of the first
tier."
As stated above, I would resolve this paradox by accepting Darwin's basic view
of pattern and causality at the first tier, but then asserting that distinct modes of
change and balances of causes, operating at higher tiers, introduce enough systematic
difference to cancel out the first tier's vector. If the first tier governs anagenesis
within populations, then the second tier features trends within monophyletic clades.
Darwinian tradition holds (as discussed