700 THE STRUCTURE OF EVOLUTIONARY THEORY
again, we grasp the need for independent macroevolutionary theory—and Buss has
supplied an important piece of the general argument with his concept of a
correlation between such major innovations and the origin of new hierarchical
levels, a theme that obviously requires the hierarchical model and cannot be
encompassed within the strict Darwinism of the Modern Synthesis. Buss concludes
(p. 188, his italics): "Synergisms between the units drove the elaboration of a
higher unit and conflicts arising between units were minimized by adaptations
limiting further variation. This conclusion has the fascinating and crucial corollary
that the major features of evolution were shaped during periods of transition
between units of selection."
THE ORGANISM-INDIVIDUAL As virtually the entire history of Darwinian
thought has unfolded under the assumption that organisms act as nearly exclusive
agents of selection (or at least that our interest in evolution centers upon the
alterations and fates of organisms), I shall not dwell upon this canonical individual
here. I want only to reemphasize the unique and decidedly peculiar features of our
kind of entity (in contrast to the characteristic properties of individuals at other
levels): maximal cohesion based on functional integration, including relatively
inflexible spatial orientations of subparts (spatiotemporal if we include
embryogenesis). This style of integrity enables the organism to be particularly
effective in suppressing selection against its interests by potential evolutionary
individuals dwelling within and forming its parts. As noted above, the virtual
"extinction" of effective cell lineage selection in complex metazoan phyla occurred
as a historical result of the evolutionary "invention" of the intricate organism—
perhaps the only example of an "endangered level" in the entire history of
evolution!
As another portentous implication of individuality in this mode, organisms
become chock full of adaptations as a consequence, under natural selection, of
building coherence by functional integration. This local phenomenon at one level
of Darwinian individuality has generated an understandable and commanding
concern with adaptation, leading to doctrines of exclusivism in extreme cases (all
too common, given our psychological preferences for simple and unifying
worldviews—a need traditionally met theologically, but sometimes, particularly in
our increasingly secular age, scientistically). If, as some strict Darwinians believe,
"organized adaptive complexity" represents both the primary result of evolution
and the cause of all other patterns in the history of life, then we will fail to
understand nature for two cardinal reasons: (1) because we have adopted a
criterion too strict even for its organismal level of most promising application (see
Chapters 10 and 11); and (2) because the criterion of "organized adaptive
complexity" does not strongly characterize the nature or definition of individuality
at most other levels of the hierarchy.
Nature's hierarchy is not fractal; each level, to express the point
metaphorically, does some things well, and other things poorly or not at all—and
the evolutionary pattern of nature features many essential things. In our mother's
house—the Earth—are many mansions. Gene selection is "good" at iterating