The Structure of Evolutionary Theory

714 THE STRUCTURE OF EVOLUTIONARY THEORY

relative frequency at all levels (with the possible exception of some dubiety about
the importance of clade selection as expressed above, and some recognition that
organismic selection has effectively squashed most cell-lineage selection in many
phyla of multicellular organisms).
I therefore end this section with two statements from George Williams (1992),
who once rejected higher-level selection with such verve and skill (1966), but who
(while properly reasserting his excellent arguments against the old form of so-
called "naive group selection," or interdemic selection in the Wynne-Edwards
modality) now strongly defends both the importance of selection at the species
level ("clade selection" of lowest rank in his terminology, because he rejects
species as units), and our lamentable failure to consider this vital process in our
previous theorizing. Echoing my methodological point that a rarity of recorded
examples does not imply any actual weakness in nature, Williams writes (1992, p.
35): "Only the barest beginnings have been made in searching the fossil record for
evidence of clade selection. The record can be searched for statistically significant
trends in diversity and abundance of particular clades ... It can also be searched for
consistent selection of certain characters."
In an expansive and forceful plea for pluralism—representing the finest form
of support that a paleontologist could obtain from colleagues engaged in the study
of microevolution—Williams (1992, p. 31) then states that allelic change in
populations cannot account for evolution because gene-pools function in nature
through their entrapment within higher-level individuals operating and interacting
as coherent and distinct entities in macroevolution.

The natural selection of alternative alleles, acting largely independently at

each locus, is the only force tending to maintain or improve adaptations

shown by the ephemeral organisms formed by the ephemeral genotypes. If

one could look back to the evolution of our own or any other sexually

reproducing species, back to well before the Cambrian, no other fitness

enhancing process of any importance would be found. Having taken that

position, I must take another. The microevolutionary process that

adequately describes evolution in a population is an utterly inadequate

account of the evolution of the earth's biota. It is inadequate because the

evolution of the biota is more than the mutational origin and subsequent

survival or extinction of genes in gene pools. Biotic evolution is also the

cladogenetic origin and subsequent survival and extinction of gene pools in

the biota.

The Grand Analogy: A Speciational Basis
for Macroevolution

PRESENTATION OF THE CHART FOR MACROEVOLUT1ONARY

DISTINCTIVENESS

When Niles Eldredge and I first formulated the theory of punctuated equilibrium in
the early 1970's (Eldredge, 1971; Gould and Eldredge, 1971; Eldredge