Structural Constraints, Spandrels, and Exaptation 1211
vs. specific design) and the sequential nature of their interaction (generic order as
given, selective order as superimposed refinement), the structural order generated by
physical necessity meshes well with the functional order built by natural selection (p.
xv): "Selection achieves and maintains complex systems poised on the boundary, or
edge, between order and chaos. These systems are best able to coordinate complex
tasks and evolve in a complex environment. The typical, or generic, properties of
such poised systems emerge as potential ahistorical universals in biology."
I have emphasized throughout this section that the unusual structuralist theme of
spontaneous order externally imposed by physical law (and therefore so different
from structuralism's conventional focus upon internal channeling set by phyletic
history, and then encoded in genetic and developmental programs) enjoys its greatest
potential strength in two areas where other styles of explanation either don't apply in
principle, or have simply (and so far) failed to yield robust results: the origin of life
and its early history up to the construction of a prokaryotic cell; and the explanation
of broad, recurrent, and potentially ahistorical, or at least not phylogenetically
constrained, patterns (the form of ecological pyramids, rather than the particular top
carnivore resident thereupon, the right skewed distribution of life's complexity rather
than the occupation of its realized neurological extremity by Homo sapiens). The
structure of Kauffman's book affirms these foci (and the resulting promise of this
approach through noninterference with the large and legitimate domain of necessarily
historical explanation).
Life's origin and precellular history occupies one of three major sections in The
Origins of Order. Kauffman stresses his message of physical necessity in designating
this set of chapters as "The Crystallization of Life." He structures his argument by
attacking a straw man that, at least in the understanding of most paleontologists, fell
from popularity more than 20 years ago when the fossil record yielded cells of
bacterial form in the most ancient sediments that could preserve organic structures
(3.5 to 3.6 billion years old). But this old and superseded claim of exceedingly low
probability for life's origin does serve as a convenient foil for Kauffman's (and
virtually the entire profession's) search for different answers rooted in the predictable
and generic nature of organic chemistry and the physics of self-organizing systems
(p. 285): "The second part of this book... explores a heretical possibility. The origin
of life, rather than having been vastly improbable, is instead an expected collective
property of complex systems of catalytic polymers and the molecules on which they
act. Life, in a deep sense, crystallized as a collective self-reproducing metabolism in a
space of possible organic reactions. If this is true, then the routes to life are many and
its origin is profound, yet simple."
Kauffman then devotes the other two sections of his book to the second theme of
broad and timeless structural generalities behind the specific adaptive solutions
crafted by the functionalist mechanism of natural selection: Part 1 on models for
interaction on rugged fitness landscapes, and Part 3 on the order of ontogeny. As an
example of structural generality behind functional specificity, Kauffman's model
predicts that the waiting time for successful