458 THE STRUCTURE OF EVOLUTIONARY THEORY
causes of macroevolution—alterations, by chromosomal repatterning, of entire
genetic systems. But, more often, he discusses macroevolutionary change as a
consequence of alterations in developmental ontogeny. His language then becomes
dramatically different. Goldschmidt now refers to the genetic basis of large,
species-forming phenotypic changes as "mutations"—and he now speaks of
conventional alterations at specific sites, not of holistic repatternings. He often
describes these mutational changes as "small," and he argues for far-reaching
consequences because genes affect rates of development, and small changes
occurring early in growth can trigger cascading results throughout ontogeny. "A
single mutational step affecting the right process at the right moment can
accomplish everything provided that it is able to set in motion the ever-present
potentialities of embryonic regulation" (1940, p. 297). These developmental
themes, of course, would be regarded as interesting and acceptable to orthodox
synthesists (however underemphasized within the traditions of this theory). "The
physiological balanced system of development is such that in many cases a single
upset leads automatically to a whole series of consecutive changes of development
in which the ability for embryonic regulation, as well as purely mechanical and
topographical moments, come into play; there is in addition the shift in proper
timing of integrating processes. If the result is not, as it frequently is, a monstrosity
incapable of completing development or surviving, a completely new anatomical
construction may emerge in one step from such a change" (1940, p. 486).
How then shall the hopeful monster be defined: the product of an illusory
systemic mutation (and therefore a chimaera to be set aside), or as the result of a
small genetic change that, by working early in ontogeny, produces a substantial
final effect (and therefore an acceptable idea to stretch the Neo-Darwinian
envelope)?
This confusion epitomizes the key issue for evaluating Goldschmidt's book,
since the importance of his macroevolutionary ideas depends upon a resolution.
Many readers have noted and commented upon this frustration, and Goldschmidt
himself remarked (1955, quoted in Frazzetta, 1975, p. 116): "I have been
reproached for not having made clear in my book The Material Basis of Evolution
whether I was speaking of systemic mutation (scrambling of the chromosomal
pattern) or of ordinary mutations of a macroevolutionary type, and of being
confused myself on what I meant."
In one sense, of course, any resolution based on Goldschmidt's own
intellectual ontogeny must admit a genuine incoherence, even a contradiction,
between the different parts of his book. After all, systemic mutations differ
markedly from small genetic changes that cascade to large effect by acting early in
ontogeny—and Goldschmidt clearly grants each phenomenon, in different
passages, the dominant role in macroevolutionary change! But I think that several
persuasive arguments can be made, including the existence of a genuine literary
"smoking gun," for regarding the developmental theme as more important, both in
Goldschmidt's career and in his 1940 book (even though systemic mutation, as a
much more radical concept—albeit ultimately