The Modern Synthesis as a Limited Consensus 505
I prefer to view the history of the Synthesis under a different rubric and
terminology developed by historian of science Will Provine and by myself—
namely, (1) restriction followed by (2) hardening, with the first process viewed as
largely admirable, the second as mostly dubious.
Provine has argued (1986) that the first phase of synthesizing, the integration
of Mendel and Darwin to a core discipline of population genetics, should be
viewed as a welcome restriction (a "constriction" in his favored term)— for
biologists could now shed the several competing and truly contradictory theories
(primarily orthogenetic and saltational) that had made the domain of evolutionary
studies seem so anarchic at the Darwinian celebrations of 1909.
But the first phase also included a vigorously pluralistic range of permissible
mechanisms within the primary restriction. The original synthesists wanted to
render all of evolution by known genetic mechanisms; but they tended to
agnosticism about relative frequencies among the legitimate phenomena, notably
on the issue of drift (and other random phenomena) vs. selection.
The second phase began with this pluralism intact, as the first wave of books
from the late 1930's and 1940's clearly illustrates. But this broad net then tightened,
as the leading synthesists promoted natural selection, first to a commanding
frequency and then to virtual exclusivity as an agent of evolutionary change. This
consensus hardened to orthodoxy, often accompanied by strong and largely
rhetorical dismissal of dissenting views—a position that reached its acme in the
Darwinian centennial celebrations of 1959. The pluralism of "consistent with
genetics" eventually narrowed to a restrictive faith in what Weismann had called
the "all-sufficiency" of natural selection, with the accompanying requirement that
phenotypes be analyzed as problems in adaptation. I almost feel as if the arbiters of
fashion and theory had distributed sandpaper to all evolutionists—and that
ordinary professional activity shifted to a vigorous smoothing out of all remaining
bumps, facets, and channels of Galton's polyhedron (see pp. 342-351), as
organisms became unfettered billiard balls, rolling wherever the pool cue of natural
selection dictated upon the crowded table of ecology.
This hardening extended beyond overconfidence in adaptation to a more
general, and sometimes rather smug, feeling that truth had now been discovered,
and that a full account of evolution only required some mopping up and
adumbration of details. The paeans of self-satisfaction penned for the 1959
centennial of the Origin (see pp. 569-576) almost invite a parody of Hamlet's
insightful comment about his mother's rhetorical overstatements: the writers
praised too much, one thinks.
Synthesis as Restriction
The Initial Goal of Rejecting Old Alternatives
William Bateson, to be sure, had his own particular axe to grind when he so
dramatically expressed his pessimism about evolutionary theory in his famous
address to the American Association for the Advancement of Science in