Species as Individuals in the Hierarchical Theory of Selection 699
as organismal devices evolved to set and stabilize the course of development as
early in ontogeny as possible, thus greatly reducing the potential for new forms of
differential cellular proliferation either to arise at all in later ontogeny, or to reach
the germ line and act in cell-lineage selection even if they do manage to originate.
Buss sums up his thesis:
Selection at the level of the individual has opposed selection at the level of
the cell lineage by acting to set the timing of terminal somatic
differentiation as far back in ontogeny as possible—whenever possible into
the maternal cytoplasm itself, (p. 5). ... The release of the totipotent
germinative lineage from the task of producing somatic tissues meant that
the number of divisions made by the totipotent lineage could be reduced
and, consequently, the opportunity for variants to arise to become severely
restricted (p. 100)... Metazoans, by the twin devices of maternal
predestination and germ-line sequestration, have effectively closed their
ontogenies to heritable intrusion arising in the course of that ontogeny. A
novel epigenetic program can only arise if a mutation of extraordinarily
improbable precision and autonomy occurs in the germ cells themselves (p.
102).But nothing can be won without a price in our complex world of interacting
levels, either in evolution or in human society. In stabilizing the organismic level
with such effective devices to suppress cellular and other forms of suborganismic
selection, organisms have greatly reduced their flexibility for future evolutionary
change of more than a superficial nature. For these mechanisms of development do
not suppress only the forms of cell-lineage selection that would harm the organism;
rather, they impede any effective cellular selection at all, whether beneficial or
harmful. These policing devices of the organism therefore close off an avenue once
open for substantial change in basic designs, thus restricting maximal potency to
the iteration of essentially similar species (as in such famous examples as the
cichlids of African lakes, or the Galapagos finches), now representing evolution in
its most vigorous contemporary mode. Ou sont les neiges d'antan? "The clear
implication is that evolution of cellular differentiation fueled the evolution of
controls over variants which fail to behave altruistically. The mechanisms, which
metazoans employ to limit the heritability of variants, which fail to contribute to
somatic functions, are blind to the traits, which a variant might express. Potentially
beneficial variants are as limited as are potentially detrimental ones" (p. 103,
Buss's italics).
This perspective implies a striking limitation upon the strictly Darwinian style
of extrapolative and gradualistic selection that the Modern Synthesis promulgated
as an adequate explanation for evolution at all scales of time and effect (see
quotation from Wilson et al. on p. 583). If Buss's views are valid, then
conventional Neo-Darwinian evolution must work within strictures of essentially
established ontogenies that can surely generate exuberant adaptive variations upon
set themes, but may be effectively unable to construct major innovations that
establish the outlines of macroevolution. Once