Is S. J. Gould a Darwinist? That depends on ones definition of
Darwinism. If Darwinism is defined as a change of flora and fauna
over time (somehow) by some (unknown) materialistic naturalistic
causes, then yes, Gould is a Darwinist. If on the other hand a
Darwinist is one who understands these changes to be more or less
as Darwin did by the gradual accumulation of species variation by
natural selection, then no, Gould is not a Darwinist.
I will reprint Gould's article in a more extent form to let each
decide for himself according to his own definition of "Darwinism."
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From:
_The Confusion About Evolution_ in "The New York Review of Books",
Nov. 19, 1992. Stephen Jay Gould's review of _The Ant and the Peacock:
Altruism and Sexual Selection from Darwin to Today_
(Cambridge U. Press, 1991) by Helena Cronin
I have argued that gene selectionism is an ultimately incorrect view
of evolutionary mechanics. But suppose it were right. Would gene
selectionism then be the fully comprehensive theory of biological
change that its advocates tout so vociferously? As a paleontologist,
working with changes in units of millions of years rather than
generations, I find this strange assertion to be the most blinkered
and untenable in the entire catalog of strict Darwinian parochialism.
Darwin himself relied crucially on such an extrapolative vision:
smoothly extend the adaptive struggles of generations across millions
of years in geological time, and you will obtain the entire wonderously
ramified tree of life. Consider two famous passages from the _Origins
of Species_:
It may be said that natural selection is daily and hourly scrutinizing,
thoughout the world, every variation, even the slightest; rejecting
that which is bad, preserving and adding up all that is good; silently
and insensibly working, whatever and wherever opportunity offers, at the
improvement of each organic being in relation to its organic conditions
of life. We see nothing of these slow changes in progress until the
hand of time had marked the long lapse of ages.
The inhabitants of each successive period in the world's history have
beaten their predecessors in the race for life, and are, in so far,
higher in the scale of nature; and this may account for that vague yet
ill-defined sentiment, felt by many paleontologists, that organization
on the whole had progressed.
If this uniformitarian vision of extrapolation fails, then we must
conclude that while adaptationism may control immediate changes in the
overt forms of organisms, it cannot render evolution at other scales.
The main excitement in evolutionary theory during the past twenty years
has not been - as Cronin would have us believe - the shoring up of
Darwinism in its limited realm (by gene selectionism or any other
patching device), but rather the documentation of the reasons why
Darwin's crucial requirement for extrapolation has failed.
Selectionism is not a general model for evolutionary change at most
scales.
In the world below organisms, at the scale of changes in nucleotides
of the DNA code, Motoo Kimura's theory of neutralism (based on the
prevalence of genetic drift, as defined earlier), combined with a
better understanding of genetic mechanisms, has demonstrated the
neutrality of much, if not most, alteration at minimal magnitude.
Selectionists often respond, as Cronin does, that their Darwinian
preferences are not thereby compromised because such neutral genetic
changes do not alter the external forms of organisms, and therefore
couldn't be 'seen' by natural selection anyway. Cronin writes:
'[Kimura's] theory also assumes that chance is an evolutionary force
but it is to do with changes at the molecular level that have no
phenotypic effects, not evolution in the sense that we are concerned
with - adaptive change.' But how can you dismiss a process that
probably accounts for more than 50 percent of all genetic change by
noting that such alterations don't manifest themselves at the level
that happens to interest you most? This special interest, after all
is just a parochialism based on human sizes and lifetimes, and on
the history of our thinking. Nature, working at so many other scales,
takes scant notice and plays no favorites. If we lived in the world
of nueleotides, we would see the random ebb and flux as fundamental
and view occasional islands of adaptive coagulation at larger scales
as peculiar exceptions in an alien domain.
But the ultimate failure of Cronin's adaptionism, as a general
evolutionary model, appears most clearly when we consider the
paleontological record. Darwin's vision may prevail in the here
and now of immediate adaptive struggles. But if we cannot extend
the small changes thereby produced into the grandeur of geological
time to yield the full tree of life, then Darwin's domain is a
limited corner of evolutionary explanation. New documentation on
the rapidity and intensity of mass extinction (including the event
that wiped out the dinosaurs) has provided the strongest argument
for rejecting Darwinian extrapolation. Darwin clearly understood
the threat, and he struggled against the implications of mass
exctinction in the _Origin of Species_ by trying to deny both their
extent and rapidity. He endeavored to spread them out in time and
diminish their effects. He attempted to render them as an
intensification of ordinary competition (inspired, perhaps, by an
increase in rates of change for conventional processes like
mountain-building and change in sea level). But if mass exctinctions
are true breaks in continuity, if the slow building of adaptation
in normal times does not extend into predicted success across mass
exctinction boundaries, then extrapolationism fails and adaptationism
succumbs.
-jpt
--John P. Turnbull (jpt@ccfdev.eeg.ccf.org)Cleveland Clinic FoundationDept. of Neurology, Section of Neurological ComputingM52-119500 Euclid Ave.Cleveland Ohio 44195Telephone (216) 444-8041; FAX (216) 444-9401