952 THE STRUCTURE OF EVOLUTIONARY THEORY
extinctions to mutational sweeps through little laboratory populations of E. coli.
Punctuational models in other disciplines: towards a general
theory of change
PRINCIPLES FOR A CHOICE OF EXAMPLES. In their symposium for the
American Association for the Advancement of Science, and in their subsequent
book, Somit and Peterson (1992) explored the wider role of punctuated equilibrium
in suggesting similar modes of change in other disciplines. (Their edited book
bears the title: The Dynamics of Evolution: The Punctuated Equilibrium Debate in
the Natural and Social Sciences.) In discussing the "manner in which punctuated
equilibrium theory renders its greatest contribution to the behavioral sciences"
(1992, p. 12), they suggested (loc. cit): "By providing a different metaphor for
explaining social phenomena, the theory may assist us in better understanding
human behavior in all of its manifestations."
I don't question either the widespread invocation or the extensive utility of the
metaphorical linkage, and I list elsewhere (pp. 976-979) a range of such
invocations across disciplines from economics to cartooning to guidelines for the
self-help movement. But in discussing the application of punctuated equilibrium to
other disciplines, I am more interested in exploring ways in which the theory might
supply truly causal insights about other scales and styles of change, based on
conceptual and structural "homologies" (as defined and discussed on pp. 928-931),
rather than broader metaphors that can surely nudge the mind into productive
channels, but that make no explicit claim for causal continuity or unification. Thus,
in discussing the influence of punctuated equilibrium upon other disciplines, I will
focus upon two kinds of potentially homological proposals.
First, where authors proceed beyond simple claims for broad similarities in
jerky tempos of change to identify additional and explicit overlaps in the set of
collateral principles that I called "conjoints" (see p. 930) in defining conceptual
homology vs. analogy—including, for example, (1) claims that link punctuations to
the origin of discretely individuated units arising by branching (a conceptual
homolog of speciation), (2) discussions of the difference between punctuational
and saltational modes, and (3) proposals about active causes for the maintenance of
stasis. And second, where authors use the similarities between punctuated
equilibrium and punctuational tempos in their own discipline to advance more than
vaguely metaphorical suggestions for general theories about the nature of change
in systems that may be said to "evolve," and to display historical continuity.
EXAMPLES FROM THE HISTORY OF HUMAN ARTIFACTS AND
CULTURES.
I presented arguments for punctuational models of human biological evolution in a
previous section (pp. 908-916). But I have also been struck by the frequency of
punctuational explanations advanced for patterns in the development