Species as Individuals in the Hierarchical Theory of Selection 627
or causal agents in the Darwinian process. This misguided search arises from a
legitimate intuition—that genes are vitally important in evolution, and clearly
central to the process of natural selection—followed by the false inference that
genes should therefore be designated as primary causes. Needless to say, no
biologist wishes to deny the centrality or importance of genes, just as this intuition
holds. But genes simply cannot operate as efficient causes in Darwin's process of
organismic selection. Genes, as carriers of continuity to the next generation, may
be designated as material causes in Aristotle's abandoned terminology. But we no
longer refer to the material aspects of natural processes as "causes." Organisms
"struggle" as agents or efficient causes; their "reward" may be measured by greater
representation of their genes, or material legacies, in future generations. Genes
represent the product, not the agent—the stuff of continuity, not the cause of
throughput.
The standard gambit of gene selectionists, in the light of this recognized
problem, invokes two arguments, both indefensible.
ATTEMPTS TO ASSIGN AGENCY TO GENES BY DENYING EMERGENT PROPERTIES
TO ORGANISMS. Once one admits, as all gene selectionists must and do, that genes
propagate via selection on organisms as interactors, how then can one possibly
ascribe direct causal agency to genes rather than to bodies? Only one logical exit
from this conundrum exists: the assertion that each gene stands as an optimal
product in its own place, and that bodies impose no consequences upon individual
genes beyond providing a home for joint action. If such a view could be defended,
then bodies would become passive aggregates of genes—mere packaging—and
selection on a body could then be read as a convenient shorthand summary for
selection on all resident genes, considered individually.
But such a reductionistic view can only apply if genes build bodies without
nonlinear or nonadditive interactions in developmental architecture. Any
nonlinearity precludes the causal decomposition of a body into genes considered
individually—for bodies then become, in the old adage, "more than the sum of
their parts." In technical parlance, nonlinearity leads to "emergent" properties and
fitness at the organismic level—and when selection works upon such emergent
features, then causal reduction to individual genes and their independent
summations becomes logically impossible. I trust that the empirical resolution of
this issue will not strike anyone as controversial, for we all understand that
organisms are stuffed full of emergent features—an old intuition stunningly
affirmed by the first fruits of mapping the human genome (see the full issues of
Science and Nature in February 2001 and my own initial reaction for general
audiences in Gould, 2001). What else is developmental biology but the attempt to
elucidate such nonlinearities? The error of gene selectionists does not lie in their
stubborn assertion of pure additivity in the face of such knowledge, but rather in
their conceptual failure to recognize that this noncontroversial nonlinearity
destroys their theory.
Dawkins admits the apparent problem (1976, p. 40): "But now we seem to
have a paradox. If building a baby is such an intricate venture, and if every