http://SaturnianCosmology.Org/ mirrored file
For complete access to all the files of this collection
see http://SaturnianCosmology.org/search.php
==========================================================
Unofficial SJG Archive
The Unofficial Stephen Jay Gould Archive
Unofficial SJG Archive
*Punctuated Equilibrium's Threefold History*
by Stephen Jay Gould
T
he "Urban Legend" of Punctuated Equilibrium's Threefold History: The
opponents of punctuated equilibrium have constructed a fictional
history of the theory, primarily (I suppose) as a largely
unconscious expression of their hope for its minor importance [?]
This supposed threefold history of punctuated equilibrium also ranks
about as close to pure fiction as any recent commentary by
scientists has ever generated. In stage one, the story goes, we were
properly modest, obedient to the theoretical hegemony of the Modern
Synthesis, and merely trying to bring paleontology into the fold.
But the prospect of worldly fame beguiled us, so we broke our ties
of fealty and tried, in stage two, to usurp power by painting
punctuated equilibrium as a revolutionary doctrine that would
dethrone the Synthesis, resurrect the memory of the exiled martyr
(Richard Goldschmidt <../people/richard_goldschmidt.html>), and
reign over a reconstructed realm of theory. But we were too big for
our breeches, and the old guard still retained some life. They
fought back mightily and effectively, exposing our bombast and
emptiness. We began to hedge, retreat, and apologize, and have been
doing so ever since in an effort to regain grace and, chastened in
stage three, to sit again, in heaven or Valhalla, with the
evolutionary elite.
Such farfetched fiction suffers most of all from an internal
construction that precludes exposure and falsification among true
believers, whatever the evidence. Purveyors of this myth even name
the three stages, thus solidifying the false taxonomy. Dawkins
(1986), for example, speaks of the "grandiloquent era?of
middle-period punctuationism [which] gave abundant aid and comfort
to creationists and other enemies of scientific truth." In the other
major strategy of insulation from refutation, supporters of this
"urban legend" about the modest origin, bombastic rise, and
spectacular fall of punctuated equilibrium forge a tale that allows
them to read any potential disconfirmation as an event within the
fiction itself. [?]
In particular, and most offensive to me, the urban legend rests on
the false belief that radical, "middle-period" punctuated
equilibrium became a saltational theory wedded to Goldschmidt's
hopeful monsters as a mechanism. I have labored to refute this
nonsensical charge from the day I first heard it. But my efforts are
doomed within the self-affirming structure of the urban legend. We
all know, for so the legend proclaims, that I once took the
Goldschmidtian plunge. So if I ever deny the link, I can only be
retreating from an embarrassing error. And if I, continue to deny
the link with force and gusto, well, then I am only backtracking
even harder (into stage 3) and apologizing (or obfuscating) all the
more. How about the obvious (and accurate) alternative: that we
never made the Goldschmidtian link; that this common error embodies
a false construction; and that our efforts at correction have always
represented an honorable attempt to relieve the confusion of others.
But the urban legend remains too simplistically neat, and too
resonant with a favorite theme of Western sagas, to permit
refutation by mere evidence. So Dennett (1995, pp. 283-284) writes:
"There was no mention in the first paper
of any radical theory of speciation or mutation. But later, about
1980, Gould decided that punctuated equilibrium was a revolutionary
idea after all [But] it was too revolutionary, and it was hooted
down with the same sort of ferocity the establishment reserves for
heretics like Elaine Morgan. Gould backpedaled hard, offering
repeated denials that he has ever meant anything so outrageous." And
Halstead (1985, p. 318) wrote of me (with equal poverty in both
logic and grammar): "He seems to be setting up a face-saving formula
to enable him to retreat from his earlier aggressive saltationism,
having had a bit of a thrashing, his current tack is to suggest that
perhaps we should keep the door open in case he can find some
evidence to support his pet theories so let us be 'pluralist.'"
I do not, of course, claim that our views about punctuated
equilibrium have never changed through the years of debate (only a
dull and uninteresting theory could remain so static in the face of
such wide discussion). Nor do I maintain a position that would be
even sillier?namely, that we made no important errors requiring
corrections to the theory. Of course we made mistakes, and of course
we have tried to amend them. But I look upon the history of
punctuated equilibrium (from my partisan vantage point of course) as
a fairly standard development for successful theories in science. We
did, indeed, begin modestly and expand outward thereafter. (In this
sense, punctuated equilibrium has grown in theoretical scope,
primarily as macroevolutionary theory developed and became better
integrated with the rest of evolutionary thought?and largely through
articulation of the hierarchical model, as discussed in the previous
chapter).
We started small as a consequence of our ignorance and lack of
perspective, not from modesty of basic temperament. As stated
before, we simply didn't recognize, at first, the interesting
implications of punctuated equilibrium for macroevolutionary
theory?primarily gained in treating species as Darwinian individuals
for the explanation of trends, and in exploring the extent and
causes of stasis. With the help of S. M. Stanley, E. S. Vrba and
other colleagues, we developed these implications over the years,
and the theory grew accordingly. But we never proposed a radical
theory for punctuations (ordinary speciation scaled into geological
time), and we never linked punctuations to microevolutionary
saltationism.
Of course we made mistakes?serious ones in at least two cases?and
the theory has changed and improved by correcting these errors. In
particular, and as documented extensively in Chapter 8, we were
terribly muddled for several years about the proper way to treat,
and even to define, selection at the level of species?the most
important of all theoretical spinoffs from punctuated equilibrium.
We confused sorting with selection (see Vrba and Gould, 1986, for a
resolution). We also did not properly formulate the concept of
emergence at first; and we remained confused for a long time about
emergence of characters vs. emergence of fitness as criteria for
species selection (Lloyd and Gould, 1993; Gould and Lloyd, 1999). In
retrospect, I am chagrined by the long duration of our confusion,
and its expression in many of our papers. But I think that we have
now resolved these difficult issues. [?]
The saltationist canard has persisted as our incubus. The charge
could never be supported by proper documentation, for we never made
the link or claim. All attempts collapse upon close examination.
Dennett, for example, who insists (1997, p. 64) that "for a while he
[Gould] had presented punctuated equilibrium as a revolutionary
'saitationist' alternative to standard neo-Darwinism," documents his
supposed best case by assuring readers (1995, p. 285) that "for a
while, Gould was proposing that the first step in the establishment
of any new species was a doozy?a non-Darwinian saltation." Dennett
directly follows this claim with his putative proof, yet another
quotation from my 1980 paper, which he renders As follows:
"Speciation is not always an extension of gradual, adaptive allelic
substitution to greater effect, but may represent, as Goldschmidt
argued, a different style of genetic change?rapid reorganization of
the genome, perhaps non-adaptive" (Gould, 1980b, p. 119).
I regard Dennett's case as pitiful, but the urban legend can offer
no better. First of all, this quotation doesn't even refer to
punctuated equilibrium, but comes from a section of my 1980 paper on
the microevolutionary mechanics of speciation. Secondly, Dennett
obviously misreads my statement in a backwards manner. I am trying
to carve out a /small/ theoretical space for a style of
microevolutionary rapidity at low relative frequency?as clearly
stated in my phrase "not always an extension of gradual?" But
Dennett states that I am proposing this mechanism as a general
replacement for gradual microevolutionary change in /all/ cases of
speciation?"the first step in the establishment of /any/ new
species" in /his/ words. But /my/ chosen phrase?"not always"?clearly
means "most of the time," and cannot be read as "never." In short, I
made a plea for pluralism, and Dennett charges me with usurpation.
Then, when I try to explain, I am accused of beating a retreat to
save face. When placed in such a double bind, one can only smile and
remember Schiller's famous dictum: /Mit/ /Dummheit/ /kimpfen/ /die/
/Gdtter/ /selbst/ /vergebens/.
Finally, the claim that we equated punctuated equilibrium with
saltation makes no sense within the logical structure of our
theory?so, unless we are fools, how could we ever have asserted such
a proposition? Our theory holds, as a defining statement, that
ordinary allopatric speciation, unfolding gradually at
microevolutionary scales, translates to punctuation in geological
time. Microevolutionary saltation also scales as a punctuation?so
the distinction between saltation and standard allopatry becomes
irrelevant for punctuated equilibrium, since both yield the same
favored result!
Moreover, the chronology of debate proves that we did not issue
disclaimers on this subject only to cover our asses as we retreated
from exaggerations of our supposed second phase, because we have
been asserting this clarification from the very beginning?that is,
from the first paper we ever wrote to comment upon published
reactions to punctuated equilibrium. Our first response appeared in
1977, long before we issued the supposed clarion call of our false
revolution in 1980. We wrote (Gould and Eldredge, 1977, p. 121),
under the heading "Invalid claims of gradualism made at the wrong
scale": "The model of punctuated equilibria does not maintain that
nothing occurs gradually at any level of evolution. It is a theory
about speciation and its deployment in the fossil record. It claims
that an important pattern, continuous at higher levels?the 'classic'
macroevolutionary trend?is a consequence of punctuation in the
evolution of species. It does not deny that allopatric speciation
occurs gradually in ecological time (though it might not?see Carson,
1975), but only asserts that this scale is a geological microsecond."
We have never changed this conviction, and we have always tried to
correct any confusion of scaling between saltation and punctuation,
even in papers written during the supposed apogee of our
revolutionary ardor, during illusory stage 2 of the urban legend.
For example, under the heading of "The relationship of punctuated
equilibrium to macromutation," I wrote in 1982c (p. 88): "Punctuated
equilibrium is not a theory of macromutation?it is not a theory of
any genetic process?It is a theory about larger-scale patterns-the
geometry of speciation in geological time. As with ecologically
rapid modes of speciation, punctuated equilibrium welcomes
macromutation as a source for the initiation of species: the faster
the better. But punctuated equilibrium clearly does not require or
imply macromutation, since it was formulated as the expected
geological consequence of Mayrian allopatry." [?]
*The Charge of Ulterior Motivation*
When charges of dishonesty or lack of originality fail, a committed
detractor can still label his opponents as unconcerned with
scientific truth, but motivated by some ulterior (and nefarious)
goal. Speculations about our "real" reasons have varied widely in
content, but little in their shared mean spirit (see, for example,
Turner, 1984; Konner, 1986; and Dennett, 1995). I will discuss only
one of these peculiar speculations?the charge that punctuated
equilibrium originated from my political commitments rather than
from any honorable feeling about the empirical world?because, once
again, the claim rests upon a canonical misquotation and exposes the
apparent unwillingness or inability of our unscientific critics to
read a clear text with care.
I have already discussed Halstead's version of the political charge
in the great and farcical British-Museum-cum-cladism-cum-Marxism
debate (see pages 984-985). The supposed justification for this
construction lies in another quotation from my writing, second in
false invocation only to the "death of the Synthesis" statement
discussed earlier (p. 1003).
I do not see how any careful reader could have missed the narrowly
focused intent of the last section in our 1977 paper, a discussion
of the central and unexceptionable principle, embraced by all
professional historians of science, that theories must reflect a
surrounding social and cultural context. We began the section by
trying to identify the cultural roots of gradualism in larger
beliefs of Victorian society. We wrote (Gould and Eldredge, 1977, p.
145): "The general preference that so many of us hold for gradualism
is a metaphysical stance embedded in the modern history of Western
cultures: it is not a high-order empirical observation, induced from
the objective study of nature . . . We mention this not to discredit
Darwin in any way, but merely to point out that even the greatest
scientific achievements are rooted in their cultural contexts?and to
argue that gradualism was part of the cultural context, not of nature."
We couldn't then assert, with any pretense to fairness or openness
to self-scrutiny, that gradualism represents cultural context, while
our punctuational preferences only record unvarnished empirical
truth. If all general theories embody a complex mixture of
contingent context with factual adequacy, then we had to consider
the cultural embeddedness of preferences for punctuational change as
well. We therefore began by writing (p. 145) that "alternative
conceptions of change have respectable pedigrees in philosophy." We
then discussed the most obvious candidate in the history of Western
thought: the Hegelian dialectic and its redefinition by Marx and
Engels as a theory of revolutionary social change in human history.
We cited a silly, propagandistic defense of punctuational change
from the official Soviet handbook of Marxism-Leninism, in order to
stress our point about the potential political employment of all
general theories of change. We concluded (p. 146): "It is easy to
see the explicit ideology lurking behind this general statement
about the nature of change. May we not also discern the implicit
ideology in our Western preference for gradualism?"
But the argument required one further step for full disclosure. We
needed to say something about why we, rather than other
paleontologists at other times, had developed the concept of
punctuated equilibrium. We raised this point as sociological
commentary about the /origin/ of ideas, not as a scientific argument
for the /validity/ of the same ideas. An identification of cultural
or ontogenetic sources says nothing about truth value, an issue that
can only be settled by standard scientific procedures of
observation, experiment and empirical test. So I mentioned a
personal factor that probably predisposed me to openness towards, or
at least an explicit awareness of, a punctuational alternative to
conventional gradualistic models of change: "It may also not be
irrelevant to our personal preferences that one of us learned his
Marxism, literally at his daddy's knee."
I have often seen this statement quoted, always completely out of
context, as supposed proof that I advanced punctuated equilibrium in
order to foster a personal political agenda. I resent this absurd
misreading. I spoke only about a fact of my intellectual ontogeny; I
said nothing about my political beliefs (very different from my
father's, by the way, and a private matter that I do not choose to
discuss in this forum). I included this line within a discussion of
personal and cultural reasons that might predispose certain
scientists towards consideration of punctuational models?just as I
had identified similar contexts behind more conventional preferences
for gradualism. In the next paragraph, I stated my own personal
conclusions about the general validity of punctuational change-but
critics never quote these words, and only cite my father's
postcranial anatomy out of context instead.
We emphatically do not assert the "truth" of this alternate
metaphysic of punctuational change. Any attempt to support the
exclusive validity of such a monistic, /a priori/, grandiose
notion would verge on the nonsensical. We believe that gradual
change characterizes some hierarchical levels, even though we
may attribute it to punctuation at a lower level?the
macroevolutionary trend produced by species selection, for
example. We make a simple plea for pluralism in guiding
philosophies?and for the basic recognition that such
philosophies, however hidden and inarticulated, do constrain all
our thought. Nonetheless, we do believe that the punctuational
metaphysic may prove to map tempos of change in our world better
and more often than any of its competitors?if only because
systems in steady state are not only common but also so highly
resistant to change.
*The Most Unkindest Cut of All*
If none of the foregoing charges can bear scrutiny, strategists of
personal denigration still hold an old and conventional tactic in
reserve: they can proclaim a despised theory both trivial and devoid
of content. This charge is so distasteful to any intellectual that
one might wonder why detractors don't try such a tactic more often,
and right up front at the outset. But I think we can identify a
solution?the "triviality caper" tends to backfire and to hoist a
critic with his own petard?for if the idea you hate is so trivial,
then why bother to refute it with such intensity? Leave the idea
strictly alone and it will surely go away all by itself. Why
fulminate against tongue piercing, goldfish swallowing,
skateboarding, or any other transient fad with no possible staying
power?
Nonetheless, perhaps from, desperation, or from severe frustration
that something regarded as personally odious doesn't seem to be
fading away, this charge of triviality has been advanced against
punctuated equilibrium, apparently to small effect. To cite a
classic example of backfiring, Gingerich (1984a, 1984b) tried to
dismiss punctuated equilibrium as meaningless and untestable by
definition?and to validate gradualism /a priori/ as "commitment to
empiricism and dedication to the principal [sic] of testability in
science" (1984a, p. 338), with stasis redefined, oxymoronically in
my judgment, as "gradualism at zero rate" (1984a, p. 338). Gingerich
then concludes (1984b, p. 116): "Punctuated equilibrium is unscaled,
and by nature untestable. It hardly deserves recognition as a
conjecture of 'major importance for paleontological theory and
practice.' . . . Hypotheses that cannot be tested are of little
value in science."
But how can Gingerich square this attempted dismissal with his own
dedication of a decade in his career to testing punctuated
equilibrium by fine-scale quantitative analysis of Tertiary mammals
from the western United States (Gingerich, 1974, 1976)? These
studies, which advanced a strong claim for gradualism, represent the
most important empirical research published in the early phase of
the punctuated equilibrium debate. Gingerich then recognized
punctuated equilibrium as an interesting and testable hypothesis,
for he spent enormous time and effort testing and rejecting our
ideas for particular mammalian phylogenies. He then argued
explicitly (1978, p. 454): "Their [Eldredge and Gould's] view of
speciation differs considerably from the traditional paleontological
view of dynamic species with gradual evolutionary transitions, but
it can be tested by study of the fossil record."
Among Darwinian fundamentalists (see my terminology
in Gould, 1997d), charges of
triviality have been advanced most prominently and insistently by
Dawkins (1986, p. 251) who evaluates punctuated equilibrium
metaphorically as "an interesting but minor wrinkle on the surface
of neo-Darwinian theory"; and by Dennett (1995, p. 290) who calls
punctuated equilibrium "a false-alarm revolution that was largely if
not entirely in the eyes of the beholders."
But a close analysis of Dawkins's and Dennett's arguments exposes
the parochiality of their judgment. They regard punctuated
equilibrium as trivial because our theory doesn't speak to the
restricted subset of evolutionary questions that, for them, defines
an exclusive domain of interest for the entire subject. These men
virtually equate evolution with the origin of intricately adaptive
organic design?"organized adaptive complexity," or O.A.C. in
Dawkins's terminology. They then dismiss punctuated equilibrium on
the narrow criterion: "if it doesn't explain the focus of my
interests, then it must be trivial." Dawkins (1984, p. 684), for
example, properly notes the implications of punctuated equilibrium
for validation of higher-level selection, but then writes:
"Species-level selection can't explain the evolution of adaptations:
eyes, ears, knee joints, spider webs, behavior patterns, everything,
in short, that many of us want a theory of evolution to explain.
Species selection may happen, but it doesn't seem to do anything
much." "Everything"? Does nothing else but adaptive organismal
design excite Dawkins's fancy in the entire and maximally various
realm of evolutionary biology and the history of life?the "endless
forms most beautiful and most wonderful" of Darwin's closing words
(1859, p. 490).
But the truly curious aspect of both Dawkins's and Dennett's charge
lies in their subsequent recognition, and fair discussion, of the
important theoretical implication of punctuated equilibrium?the
establishment of species as Darwinian individuals, and the
consequent validation of species sorting
and selection
as a prominent process in a hierarchical theory of Darwinian
evolution. In 1984, Dawkins acknowledged that this aspect of
punctuated equilibrium "does, in a sense, move outside the
neo-Darwinian synthesis, narrowly interpreted. This is about whether
a form of natural selection operates at the level of entire
lineages, as well as at the level of individual reproduction
stressed by Darwin and neo-Darwinism."
In his 1986 book
,
Dawkins then devotes a substantial part of the chapter following his
rejection of punctuated equilibrium to an evaluation of species
selection. But he finishes his exploration by reimmersion in the
same parochial trap of denying importance because the phenomenon
doesn't explain his exclusive interest in adaptive organismal
design: "To conclude the discussion of species selection, it could
account for the pattern of species existing in the world at any
particular time. It follows that it could also account for changing
patterns of species as geological ages give way to later ages, that
is, for changing patterns in the fossil record. But it is not a
significant force in the evolution of the complex machinery of life
. . . As I have put it before, species selection may occur but it
doesn't seem to do anything much!" (Dawkins, 1986, pp. 268-269). But
doesn't "the pattern of species existing in the world at any
particular time" and "changing patterns in the fossil record"
represent something of evolutionary importance?
At the end of his long riff against punctuated equilibrium, Dennett
also pauses for breath and catches a glimmer of the concept that
seems important and theoretically intriguing to many students of
macroevolution (Dennett, 1995, pp. 297-298):
The right level at which to look for evolutionary trends, he
[Gould] could then claim [indeed I do], is not the level of the
gene, or the organism, but the whole species or clade. Instead
of looking at the loss of particular genes from gene pools, or
the differential death of particular genotypes within a
population, look at the differential extinction rate of whole
species and the differential "birth" rate of species?the rate at
which a lineage can speciate into daughter species. This is an
interesting idea . . . It may be true that the best way of
seeing the long-term macro-evolutionary pattern is to look for
differences in "lineage fecundity" instead of looking at the
transformations in the individual lineages. This is a powerful
proposal worth taking seriously.
I am puzzled by the discordance and inconsistency, but gratified by
the outcome. Dawkins and Dennett, smart men both, seem unable to
look past the parochial boundaries of their personal interest in
evolution, or their feelings of jealousy towards whatever
effectiveness my public questioning of their sacred cow of Darwinian
fundamentalism may have enjoyed (see Gould, 1997d
)?so they must brand
punctuated equilibrium as trivial. But they cannot deny the logic of
Darwinian argument, and they do manage to work their way to the
genuine theoretical interest of punctuated equilibrium's major
implication, the source of our primary excitement about the idea
from the start.
[ Stephen Jay Gould, /The Structure of Evolutionary Theory/
, Cambridge,
Massachusetts: Harvard University Press, 2002, pp. 1006-1021. ]
------------------------------------------------------------------------
Home Page | Further Reading
<../bibliography.html> | Site Map <../sitemap.html> | Send
Feedback <../feedback.html>