834 THE STRUCTURE OF EVOLUTIONARY THEORY
our present circumstances). When we realize that the cave painters of Chauvet,
Lascaux, and Altamira do not differ from us in any phenotypic features, their
stunning achievement seems less mysterious. For the two more substantial cases,
the 0.9 to 1.0 million years of stasis in the first well documented hominid species,
Australopithecus afarensis (aka "Lucy"), has been presented with much data and
commentary (Kimbel, Johanson and Rak, 1994; see discussion of popular
misapprehensions in Gould, 1995). Grine (1993) has also recorded 0.8 million
years of stasis in Australopithecus robustus from Swartkrans cave in South Africa.
I am, in any case, gratified to note the changing presuppositions of this small,
contentious and vital field of paleoanthropology. In early years of this debate, after
refuting the Cronin et al. (1980) hypothesis, Jacobs and Godfrey (1982, p. 85)
wrote: "The Hominidae can no longer be blissfully assumed to be safely above the
punctuationist challenge to the gradualist orthodoxy." Just twelve years later,
McHenry could assert in the closing line of his review (1994): "It is interesting,
however, how little change occurs within most hominid species through time."
This elevation of stasis to visibility, respectability and even to expectation has
generated subtle and interesting repercussions for gradualism. When gradualism
enjoyed high status as a virtually definitional consequence of evolution itself, few
researchers thought to question such an anticipated result (but simply rejoiced in
any rare instance of affirmation). However, once stasis emerges as an alternative
norm, with gradualism designated as uncommon by the same analysis, then
gradualism itself must fall under scrutiny for the first time.
With this shift of perspective, a paradox that should have been obvious from
the start finally emerged into clear view: gradualism, prima facie, represents a
"weird" result, not an anticipated and automatic macroevolutionary expression of
natural selection—thus, perhaps, accounting for its rarity. Geological gradualism
operates far too slowly to yield any workable effect at all when properly scaled
down and translated to the immediacy of natural selection in local populations!
(See Jablonski, 1999, for a forceful assertion of this paradox.)
Again, we encounter the major dilemma that I call (Gould, 1997f) "the
paradox of the visibly irrelevant"—that is, phenomena prominent enough to be
detectable and measurable at all in local populations during ordinary human time
must cascade to instantaneous completion when scaled into geological time,
whereas truly gradual effects in geological time must be effectively invisible at
scales of human observation in ecological time. Consequently, what we see in our
world can't be the direct stuff, by simple extrapolation, of sustained
macroevolutionary change—while what we view as slow and steady in the
geological record can't be visible at all (in the same form) by the measuring rod of
our own life's duration.
Eldredge and I first raised this point explicitly in 1977 (Gould and Eldredge,
1977), for we had missed this implication in our original formulation of 1972.
Here, on this issue, we finally caught the attention of many