Seeds of Hierarchy 203
that is, personal selection, must depend"). However, spurred by Spencer's critique,
he soon expanded the boundaries of selection to include other levels of nature's
hierarchy.
THE PROBLEM OF DEGENERATION AND WEISMANN'S IMPETUS
FOR GERMINAL SELECTIONAs discussed in the last chapter, the primary and standard refutation of Darwinism
by late 19th century evolutionists held that natural selection could eliminate, but
not create—and that some other factor must therefore be identified to explain the
origin of adaptations and species. For example, T. H. Morgan wrote in 1905,
before he became a Darwinian: "It appears that new species are born; they are not
made by Darwinian methods, and the theory of natural selection has nothing to do
with the origin of species, but with the survival of already formed species" (in
Kellogg, 1907, p. 95).
Darwinians, of course, understood this challenge, and responded with the
argument that differential survivals, long cumulated, produce gradual and
substantial changes meriting the designation "creative." Weismann himself, for
example (1896, p. 1), spoke of "the opposition of our own day, which contends that
selection cannot create but only reject, and which fails to see that precisely through
this rejection its creative efficiency is asserted."
On this contentious question of creativity, several standard anti-Darwinian
arguments invoked the earliest stages of features easily recognized as adaptive in
their perfected form, for selection can preserve and accentuate a feature fully in
place, but how can an organism move from an initial "there" to a fully functional
"here"? Two claims predominated (see Mivart, 1871, for the classic statement that
provoked Darwin's own response in later editions of the Origin): first, that initial
steps are too small to provide any conceivable benefit in selection; and second, that
earliest stages cannot initiate the final function in any sense (a bird cannot fly with
5 percent of a wing).
Darwinians developed satisfactory responses to both arguments about
incipient stages of useful structures—the palpable value of tiny benefits for the
first, and the principle of functional shift (preadaptation) for the second (see
extensive discussion in Chapter 11, pp. 1218-1246). But the same problem seemed
far more acute for the opposite dilemma of degeneration. Incipient stages of useful
structures posed enough difficulties, although ultimate adaptiveness did suggest a
Darwinian solution. But what conceivable pressure of natural selection could
account for gradual stages in the disappearance of a functionless organ—for loss
of function should remove a structure from the domain of selection entirely, and
knowledge about an eventually adaptive state could not be invoked to guide an
explanation for intermediary stages along such a functionless path.
(We might designate this problem by its classic example—the complete
disappearance of eyes in some cave fishes. Despite a century of adequate
Darwinian explanation, this issue continues to provide a rallying point for
vernacular Lamarckism. I can testify to this in a personal way. As a result of