Species as Individuals in the Hierarchical Theory of Selection 689
I close this woefully insufficient commentary by reemphasizing the point that
our discomfort or disinterest in random change largely reflects the peculiarity of
the individual and level that we know best—organisms—and does not record any
rarity or impotence for stochastic forces as agents of phyletic change in evolution.
Processes of drift probably exert least influence upon the organismic level, for the
two reasons cited earlier: large population sizes, and a style of individuality that
forges coherence by strict functional coordination of subparts, and therefore makes
nearly every trait of the organism subject to selection strong enough to overwhelm
drift.
But the organism is a unique and peculiar kind of individual—and these
strictures upon drift do not apply so strongly at any other level. We have seen, in
this section, how structural features of DNA impose neutrality or near-neutrality
upon selection at a large percentage of sites, perhaps a majority. For this reason
(and not by limitation of population size), randomness becomes a fundamental
process of evolutionary change at the genie level, however weak such a force may
be (or, indeed, may not be!) at the organismic level. We shall see that, at the
highest levels of species and clades, randomness again attains a high relative
frequency—but this time mostly as a result of low N for species in clades. If such
different causes grant randomness a high relative frequency at several important
levels of evolution's hierarchy—and if we can only assert low relative frequency at
one level, and for reasons rooted in the peculiar character of individuality in this
realm alone—then have we not committed a great conceptual error, and seriously
narrowed our general view of evolution and the history of life, by giving short
shrift to this most obvious of all alternatives to selection as a cause of change?
TRUE GENIC SELECTION. When future historians chronicle the interesting
failure of exclusive gene selectionism (based largely on the confusion of
bookkeeping with causality), and the growing acceptance of an opposite
hierarchical model, I predict that they will identify a central irony in the embrace
by gene selectionists of a special class of data, mistakenly read as crucial support,
but actually providing strong evidence of their central error. Gene selectionists
have always welcomed genuine cases of a phenomenon that they then falsely
generalize to all evolution—that is, differential proliferation of genes within
genomes for reasons acting at the genic level, and independent of effects
introduced by downward causation from selection at any higher level.
Gene selectionists have naively embraced these examples as apparent
confirmations of their belief that effectively all selection operates at this lowest
level. If genes can work their magic even without a boost from the vehicles they
usually employ as lumbering robots subject to their will, then our appreciation for
their omnipotence can only increase. But such superficial admiration obscures a
true distinction that actually illustrates the bankruptcy of exclusive gene
selectionism. These examples do not showcase the maximal power of a ubiquitous
phenomenon; rather, and quite to the contrary, they represent the only class of
instances where pure and untrammeled gene selection can operate at all!
As argued previously in this chapter (pp. 613-644), when gene selectionists