Glorious Contingency (excerpt)
by Michael Shermer
tephen Jay
Gould's Wonderful Life: The Burgess Shale and the Nature of History,
has become something of a watershed for those who study contingency and
complexity, especially applied to organisms, societies, and history, and
discussions of it can be found in many works. Walter Fontana and Leo Buss,
for example, ask in the title of their chapter "What Would Be Conserved If
'The Tape Were Played Twice'?" This is a direct reference to Gould's
suggestion in Wonderful Life that if the tape of life were rewound to
the time of the organisms found in the Canadian outcrop known as the Burgess
Shale, dated to about 530 million years ago, and replayed with a few
contingencies tweaked here and there, humans would most likely never have
evolved.
So powerful are the effects of contingency that a small
change in the early stages of a sequence can produce large effects in the
later stages. Edward Lorenz calls this the butterfly effect and by now the
metaphor is well known: A butterfly flaps its wings in Brazil, producing a
storm in Texas. The uncertainty, of our past and unpredictability of our
future created by contingency is what makes this such a challenging idea to
historians and scientists, whose models and laws call for a search for
unifying generalities, not capricious happenstances.
Gould's dangerous idea, therefore, did not go unnoticed.
Stuart Kauffman, one of the pioneers of complexity in explaining the
self-organization of complex systems, references Gould and Wonderful
Life and asks about the Cambrian explosion of life: "Was it Darwinian
chance and selection alone…or did principles of self-organization
mingle with chance and necessity"? Mathematicians Jack Cohen and Ian
Stewart published a feature story on "Chaos, Contingency, and Convergence"
in Nonlinear Science Today, centered around Wonderful Life.
Wired magazine's Kevin Kelly devotes several pages to Gould's
contingency. Philosophers also got in on the discussion. Murdo William
McRae published a critique entitled "Stephen Jay Gould and the Contingent
Nature of History." And, most exhaustively, Daniel Dennett devoted a
Brobdingnagian chapter to Gould and this idea in his book Darwin's
Dangerous Idea.
Most of these authors have criticisms of Gould's theory,
and some are valid. Fontana and Buss contend that plenty would be conserved
if the tape were rerun again. Kauffman argues for necessitating laws of
self-organization that defy contingency. Cohen and Stewart point out:
"Nowhere in Wonderful Life does Gould give an adequate treatment of
the possible existence of evolutionary mechanisms, convergences, universal
constants, that might constrain the effects of contingency." Kelly has
actually run Gould's thought experiment in a sandbox with contrary results:
"First thing you notice as you repeat the experiment over and over again,
as I have, is that the landscape formations are a very limited subset of
all possible forms." McRae concludes. "Gould's argument for contingency
ultimately returns to the notions of progress and predictability it set out
to challenge." And Dennett calls Gould "the boy who cried wolf," a "failed
revolutionary," and a "refuter of Orthodox Darwinism."
One of the surprising things about all of these
criticisms is that they appear to have missed or misunderstood the meaning
of contingency and what Gould believes is its relationship to necessitating
laws of nature. The reason for these misunderstandings is twofold. The first
is the problem of meaning—contingency does not mean random, chance, or
accident. The second is the problem of emphasis—contingency does not
exclude necessity. Identifying and solving these problems can not only show
us what is right about Gould's dangerous idea, but also helps us understand
how to find meaning in a contingent universe.
The Problem of Meaning
Many of those who oppose the idea of a predominantly
contingent universe have misread contingency for accidental or random. Jack
Cohen and Ian Stewart, for example, have stated explicitly that, "The
survivors, who produced us, did so by contingency, by sheerest accident;"
"Gould [argues] that contingency—randomness—plays a major role in
the results of evolution…", and Gould "sees the evolution of humanity
as being accidental, purely contingent." Yet Gould states quite clearly in
Wonderful Life:
I am not speaking of randomness, but
of the central principle of all history—contingency. A
historical explanation does not rest on direct deductions from laws of
nature, but on an unpredictable sequence of antecedent states, where
any major change in any step of the sequence would have altered the final
result. This final result is therefore dependent, or contingent, upon
everything that came before—the unerasable and determining signature
of history. [Emphasis added.]
As Gould notes, contingency is an unpredictable
sequence of antecedent states, not randomness, chanciness, or
accident.
Daniel Dennett likewise takes Gould to task in a chapter
entitled "Tinker to Evers to Chance," a play on words linking Gould's love
of baseball—the three names represent the most famous double-play
combination in baseball history—to chance, which Dennett identifies
with contingency. But contingency does not mean chance, nor does it mean
random, despite Dennett's conclusion: "The fact that the Burgess fauna were
decimated in a mass extinction is in any case less important to Gould than
another conclusion he wants to draw about their fate: their decimation, he
claims, was random." True, mass extinctions may seem random, as when
an asteroid hits the Earth. But by contingency Gould means a conjuncture of
preceding states that determine subsequent outcomes. just as astronomers
knew exactly when and where Comet Shoemaker-Levy 9 was going to strike
Jupiter in July of 1995 (and nailed the timing and location precisely),
astronomers from (say) Mars, observing Earth 65 million years ago could have
calculated the collision with the Yucatdn peninsula with pinpoint accuracy.
But the effects of those impacts could not have been adequately computed
(and in the case of the Jupiter hit were not), because of the number of
contingencies involved.
The eventual rise of Homo sapiens, is even more
contingent with millions of antecedent states in our past. Each
event in the sequence has a cause, and thus is determined, but the eventual
outcome is unpredictable because of contingency, not randomness or chance.
The Burgess extinction may have been determined, but the sequence of events
leading up to it, and those following, all the way to humans, were
contingent. On this point Dennett says he is confused about what Gould means
by "we" when he says we would not be here again if we reran the tape:
There is a sliding scale on which Gould
neglects to locate his claim about rewinding the tape. If by "us" he meant
something very particular—Steve Gould and Dan Dennett, let's
say—then we wouldn't need the hypothesis of mass extinction to
persuade us how lucky we are to be alive.…If, at the other extreme,
by "us" Gould meant something very general, such as "air-breathing,
land-inhabiting vertebrates," he would probably be wrong.
Dennett's confusion seems, well, confusing. By "we"
Gould means the species Homo sapiens, no more, no less, and he has
stated so on numerous occasions,
including in Wonderful Life: "Replay the tape a million times from
a Burgess beginning, and I doubt that anything like Homo sapiens
would ever evolve again."
One might claim that these misunderstandings are caused
by the fact that Gould has not offered a formal definition of contingency.
That is true, so one must read him broad and deep. But it is there in dozens
of examples and several informal definitions. In his essay
"The
Panda's Thumb," Gould shows that the thumb—actually the radial
sesamoid bone of the panda's wrist—is not a predictable design of
nature's necessitating laws of form, but an improved contraption
constructed from the history of what came before. […]
The Problem of Emphasis
In the philosophy of history journal Clio, Murdo
William McRae writes: "In spite of all his dedication to contingency and its
attendant questioning of progress and predictability, Gould equivocates
often enough to cast doubt upon the depth of his revolutionary
convictions.…At times he insists that altering any antecedent event, no
matter how supposedly insignificant, diverts the course of history; at other
times he suggests that such antecedents must be significant ones." The
reason for the apparent "equivocation" is that Gould knows contingency
interacts with necessity, but in his writings he sometimes emphasizes
the former over the latter to make a particular point. Again, Gould does not
offer a formal definition of necessity, yet it is there in his writings.
After he first defined what he meant by contingency, in 1987, he immediately
noted that "incumbency also reinforces the stability of a pathway once the
little quirks of early flexibility push a sequence into a firm channel.
Stasis is the norm for complex systems; change, when it happens at all, is
usually rapid and episodic." And in Wonderful Life Gould asks and
answers the question of emphasis:
Am I really arguing that nothing about life's
history could be predicted, or might follow directly from general laws of
nature? Of course not; the question that we face is one of scale, or level
of focus. Life exhibits a structure obedient to physical principles. We do
not live amidst a chaos of historical circumstance unaffected by anything
accessible to the "scientific method" as traditionally conceived. I suspect
that the origin of life on earth was virtually inevitable, given the
chemical composition of early oceans and atmospheres, and the physical
principles of self-organizing systems.
Daniel Dennett goes much farther, accusing Gould of
attempting to refute the quintessential driving mechanism of evolution
itself, natural selection: "Can it be that Gould thinks his thesis of
radical contingency would refute the core Darwinian idea that evolution is
an algorithmic process? That is my tentative conclusion." It is hard to
imagine how Dennett came up with this notion since it is not to be found
in Gould's writings. The problem, it would seem, stems from the fact that
when one wants to emphasize a previously neglected facet of nature,
it might appear that something is being displaced. I asked Gould about
Dennett's charge and he responded as follows:
My argument in Wonderful Life is
that there is a domain of law and a domain of contingency, and our
struggle is to find the line between them. The reason why the domain of
contingency is so vast, and much vaster than most people thought, is not
because there isn't a lawlike domain. It is because we are primarily
interested in ourselves and we have posited various universal laws of
nature. It is because…we want to see ourselves as results of
lawlike predictability and sensible products of the universe in that
sense.
To distance his pure Darwinism from Gould's
contingently modified version, Dennett makes an intriguing distinction
between two types of metaphorical building devices: skyhooks, or
"miraculous lifters, unsupported and insupportable," and cranes,
"no less excellent as lifters, and they have the decided advantage of
being real." Skyhooks are for wishful-thinking whimps who can't handle
the cold, hard reality of natural selection's crane: "A skyhook is
a 'mind-first' force or power or process, an exception to the principle
that all design, and apparent design, is ultimately the result of
mindless, motiveless mechanicity. A crane, in contrast, is a
subprocess or special feature of a design process that can be demonstrated
to permit the local speeding up of the basic, slow process of natural
selection, and that can be demonstrated to be itself the predictable (or
retrospectively explicable) product of the basic process." Dennett accuses
Gould of trying to sneak in a skyhook while he and his brave
brethren—the unalloyed Darwinians—face the crane maker with
brutal honesty. In fact, Dennett spends no less than fifty typeset pages
trying to convince his readers that Gould is a skyhooker. Me thinks the
gentleman doth protest too much. In my opinion, Dennett, and some others
who adhere to a strict Darwinian adaptationist program, may be trying to
find in nature a nonexisting pattern that shows us—Homo
sapiens—as the nearly inevitable result of evolution. Dennett's
crane of relentless natural selection is, for him, a skyhook—"a
'mind-first' force or power or process" that, run over and over, would
produce us again and again.
[ Michael Shermer,
How We Believe:
The Search for God in an Age of Science, New York: W. H. Freeman, 1999,
pp. 216-224. ]
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