Punctuated Equilibrium and the Validation of Macroevolutionary Theory 953
of human artifacts and cultural history, processes that must "evolve" under causes
and mechanisms quite different from the genetic variation and natural selection
that regulate our Darwinian biology. Moreover, the Lamarckian character of
human cultural change—the inheritance by teaching of useful innovations acquired
during the life of an inventor—provides an entirely plausible mechanism for a
more accumulative, progressive and gradual style of change in this realm than the
Darwinian character of physical evolution (and the explicit denial of Lamarckian
effects) should permit for the history of our anatomical changes. Thus, the
discovery of punctuational patterns in cultural change might be viewed as even
more surprising than the application of punctuated equilibrium to our
morphological evolution.
For example, although more gradual and accumulative change may prevail in
the history of tools following the origin of Homo sapiens (and, one presumes, a
markedly increased capacity for cultural transmission), many scholars have noted,
usually with surprise, a remarkable lack of change in the Homo erectus tool kit
during more than a million years. For example, Mazur (1992, p. 229; see also
Johanson and Edey, 1981, and Roe, 1980) states: "the early tool cultures were
remarkably stable over long periods of time. The constancy of the Acheulean
handax tradition has been especially noted, for hand axes have been found at sites
widely separated in distance and across a million years of Homo erectus's
existence look very similar to one another, their uniformity more striking than
regional differences." Such collateral data support a view of Homo erectus as an
individuated biological species, an entity rather than an arbitrarily defined segment
of a continuity in anagenetic advance.
The history of scholarly research on European Paleolithic cave art provides an
especially interesting example of how belief in progressivistic and gradual
anagenesis can operate as a limiting preconception, and how punctuated
equilibrium can play a salutary role as a potential corrective, or at least as a source
of novel hypotheses for consideration. No aspect of the prehistory of artifacts has
stunned or moved modern humans more than the parietal (wall) art of the great
caves of Lascaux, Altamira, and many others, with their subtle and beautiful
animal paintings that establish an immediate visceral link of aesthetic equality
between the anonymous prehistoric artists and a Leonardo or Picasso. At least by
standards of human history, these caves span a considerable range of time, from
Chauvet at greater than 30,000 years BP (by radiocarbon evidence) to several at
about 10,000 years of age.
Unsurprisingly, all great scholars of cave art have wanted to learn if any
"evolution" can be discerned in the temporal sequence of these images. Two
preeminent scientists built sequential schools of thought that virtually define the
intellectual history of this subject in the 20th century. These men, the Abbe Henri
Breuil and Andre Leroi-Gourhan, shared a firm belief that gradualistic evolution
through a series of progressive stages provides a primary organizing theme for the
history of parietal art (see Gould, 1998b, for an epitome of their beliefs), even
though, in other philosophical respects, their