The Modern Synthesis as a Limited Consensus 507
for adaptation, or by denying the primacy of functionalism, and proposing a
dominant role for internal, structuralist shaping of evolutionary change. Provine
(1983) has designated the first phase of synthesis as a restriction because the fusion
of Darwin with Mendel validated the rejection of all three Kelloggian alternatives,
and in both of their more general categories.
ALTERNATIVE THEORIES OF FUNCTIONALISM. Most importantly, this first-stage
fusion finally gained enough knowledge and proof to depose the longest and most
severe of all challenges to Darwinism—the doctrine that preceded natural
selection, and that Darwin himself had both accepted as a subsidiary player and
granted an ever-increasing role through subsequent revisions of The Origin of
Species. This so-called, if misnamed, "Lamarckian" theory of soft inheritance and
direct production of adaptation by inheritance of acquired characters, had
stubbornly persisted through all vicissitudes of evolutionary debate to remain a
favorite in certain circles (at least among field naturalists, if not among
experimentalists) well into the 1920's.
Mendelians had always rejected Lamarckism as inconsistent with the
mechanisms of inheritance, but Darwinians before the synthesis had generally
downplayed, ignored or actively rejected Mendelism. The first-stage fusion finally
gave Darwinian functionalists a tight rationale for outright rejection of this
alternative Lamarckian route to adaptation. This clear solution struck most
Darwinians as far more satisfactory than the uneasy pluralism that functionalists
(including Darwin himself) had been forced to espouse before—for Darwinism and
Lamarckism, as pathways to the same result of adaptation, had coexisted no more
peacefully than most competitors for the same prize. An old motto proclaims that
the enemy without should always be preferred to the enemy (or apparent helpmate)
who saps your strength from within. *
DEMOTING INTERNALISM. The dismissal of Lamarckism left two strong
alternatives in Kellogg's triad: saltationism and orthogenesis (see Chapters 4 and
5). These two challenges to Darwinian functionalism have always been linked in
their common focus on internal sources of change and direction—as jointly
embodied in the metaphor of Galton's polyhedron (see Chapter 5. The
reformulation of Mendelism as a source for pervasive, small-scale, continuous
variability (and not only for mutations of substantial extent) provoked a strong
distaste for saltationism, as early population geneticists
*In writing only these two paragraphs on this dismissal of Lamarckism, I imply no
judgment about relative historical importance. Scarcely any event in the history of
evolutionary theory could be more vital or central than the formulation of a rationale for
expunging from orthodoxy (and rendering virtually inconceivable in theory) the most
venerable of all evolutionary mechanisms. I downplay this subject here only because this
book treats the history of valid auxiliaries and alternatives to strict Darwinian
functionalism—and Lamarckism, as an invalid functionalism, therefore becomes tangential
to my concerns on both grounds (while remaining central to the larger, general history of
evolutionary theory). Similarly, this chapter gives relatively little space to the formulation of
the Modern Synthesis for the same reason: this history, so well covered in other sources
(Provine, 1971; Mayr and Provine, 1980), specifies the formulation of modern orthodoxy,
while this book treats the persistent sources of heterodoxy.