200 THE STRUCTURE OF EVOLUTIONARY THEORY
evidence that he ever clearly conceptualized the issue of levels in selection.
Wallace felt entirely comfortable with selection on all levels (see Kottler, 1985)
and never seemed to grasp either the logic of Darwin's central commitment to the
organismal level, or the problems involved in claiming that selection on other units
(particularly higher "individuals") could be effective in the face of strong selection
at the organismal level. Wallace maintained such an unshakable and primary
commitment to the ubiquity of good design that he unhesitatingly invoked higher
levels to preserve an argument for active selection whenever a focus on organisms
raised the specter of nonadaptation (notably in his uncritical advocacy of species
selection for sterility in interspecific crosses, rather than accepting Darwin's
argument for infertility as a side consequence of accumulated differences in two
diverging populations—see pp. 131-132).
But August Weismann represents the ideal test case for my assertion. Once he
had declared war on "Lamarckian" inheritance, Weismann dedicated his
professional life to promoting the Allmacht of selection. He grasped the logic of
Darwin's argument in all its details and extensions. He recognized the centrality of
selection on organisms, and he struggled to make Darwin's single-level theory
work for all phenomena of evolution. His famous 1893 paper on the Allmacht of
selection presents, as its central theme, an explicit defense for exclusivity of the
organismal level—or "personal selection" in his terms. * Later, and largely in
response to strong arguments made by Spencer, Weismann admitted that he could
not rely on personal selection alone. He could continue to promote Allmacht only
by recognizing another level of "germinal selection" for subcellular components of
the germplasm.
Moreover, Weismann gradually extended the theory of germinal selection,
from an ad hoc aid for personal selection (in the original formulation of 1895 and
1896) to a fully articulated theory of hierarchy replete with notions of
independence and conflict between levels (1904 version). Finally, Weismann came
to regard hierarchical selection as the linchpin and completion of his entire theory
(see pp. 221-224)—though we have forgotten his cogent arguments, and usually
depict him as the champion of conventional, organismic selection. Weismann's
intellectual journey, his relentless probings and frequent reformulations, leading
finally (and perhaps inexorably) to a full theory of hierarchy, provide an object
lesson in the logic of evolutionary argument,
- Meaning, of course, not subjectivity in argument, but selection on organisms, or per-
sons. This term became popular in Germany via Haeckel's theory of structural hierarchy (see
pp. 208-210, this chapter), in which the body of an organism—Eine Person—enjoyed no
special status, but merely represented one level of a six-tiered system ranging from "plastids"
(subcellular parts) to "corms" (colonies). I rather wish that we could use this strong, jargon-
free term today—for I would gladly adopt "personal selection" in preference to "organismal
selection." But "personal" encompasses, alas, too wide a range of different meanings in the
American vernacular, and I therefore desist. This charming term of ordinary language has
held fast in at least one area, however. The parts of siphonophores (entire organisms by
homology) are called "persons"—even in technical literature, where we can read about
"polyp persons" and "mudusa persons" as "organs" of the differentiated colony.