1290 THE STRUCTURE OF EVOLUTIONARY THEORY
an odd and inappropriately anthropocentric term, designating one subtype in the large
and general category of features established for good causal reasons at one level that
then impose effects at other times, or upon other levels, either positively (as in
"preadaptation") or negatively (as in "opportunism" for immediate advantages,
leading to extinction in the long run). Moreover, although the term has been fading
from use of late, all textbooks of evolution used to include an explicit section on a
phenomenon called "overspecialization"—another nonsense phrase devised to treat,
when theory lacked the proper concepts, the important observation that many
organismal adaptations impose inadaptive effects as spandrels upon the
encompassing species-individual. What in this pairing could possibly be called
"overspecialization" with any justification? The organism becomes adaptively
specialized to its own immediate benefit, and the species suffers as a nonadaptive
(ultimately inadaptive) side consequence of spandrels representing the adaptation's
expression at the species level. *
But I don't want to leave the impression that upwardly-injected cross-level
spandrels always spell dissolution, or even doom, at the higher level—and that the
species-level, in particular, suffers from this phenomenon, even to the point of
becoming a weakened or ineffective locus of evolution thereby (for such a conclusion
would greatly compromise the hierarchical theory itself by an argument akin to
Fisher's rejected claim (see pp. 644 - 652) for the logical ineluctability, but practical
insignificance, of species selection). Two related arguments reinforce the
evolutionary importance of cross-level spandrels, while also reaffirming the power of
the species-individual as a biological agent in evolution.
- We must not view upwardly cascading effects as uniquely detrimental for
species, but generally neutral or even positive at other levels. I suspect, rather, that a
majority of upwardly cascading effects will be negative at any higher level of
expression. Indeed, as argued previously, we have long recognized this phenomenon
as a fundamental property of Darwinism (though, again, we have lacked the
conceptual apparatus for explaining the results in these appropriate terms). The
phenotypic expressions of mutations are spandrels at the organismal level, and we
have long recognized the vast majority as deleterious for the organism. But we do not
regard this inevitable property (of anything injected adventitiously into a different
level) as globally detrimental to organisms. Populations of organisms are large
enough, and the generational cycling time of organisms short enough, to tolerate a
substantial load of general disadvantage in exchange for the occasional opportunity
- In some way, and through a very dark glass, I had some inkling of this problem as
an undergraduate. In an initial embarrassing episode of juvenilia, my first undergraduate
term paper in an evolutionary course, I treated this very subject, but could proceed no
further than suggesting the more appropriate description of "ultraspecialization," having at
least recognized that the process commits no active "wrong." In some psychological sense
that I feel strongly but cannot clearly define, I view the genesis of this entire book as
personal expiation for the puerility of this initial effort!