Speaking Out for Paleontology (excerpt)
by Michael Ruse
arly in
December of 1981, the federal courtroom in Little Rock, Arkansas, was packed.
It was the first week of a trial brought on by the American Civil Liberties
Union to challenge the constitutionality of a state law passed earlier that
year. The law mandated "balanced treatment," in the publicly supported
schools, between evolutionary ideas and so-called Creation Science, better
known as the early chapters of Genesis taken absolutely literally (Ruse 1988).
By the end of the third day, the case for the plaintiffs was going well.
Theologians had testified that Christianity had long interpreted the Bible
metaphorically; a philosopher (me!)
had
argued that Creation Science fails every criterion of demarcation between
science and pseudo-science; and the scientists were pointing to error after
error in the claims of the literalists.
Out at supper that night, everyone started to relax, and
the wine flowed freely. Someone struck up a hymn—one of those stirring
melodies from the Baptist South—ironically at first, but before long
all were joining in with vigor. No voice was louder than that of Stephen Jay
Gould: paleontologist, skeptic, Jew, New Yorker, Harvard professor, baseball
fanatic. But then, no voice is ever louder than that of Steve Gould, which
is a major reason why he is the best-known evolutionist in America today.
Located in the Museum of Comparative Zoology at Harvard
University, Stephen Jay Gould rivals Richard Dawkins in his fame as a
popularizer of evolution. His Ever Since Darwin, a collection of essays
published in 1977, was a bestseller, as have been several of his books since,
especially Wonderful Life, his work on the long-lost organisms of the
Burgess Shale,
an outcrop in the Canadian Rockies. On the bestseller lists recently was
Full House: The Spread of Excellence from Plato to Darwin,
a work which shows how the nonexistence for nearly sixty years of
.400 hitters in baseball has much to tell us about life's history.
Although this last work in particular
was as popular as can be, Gould would be insulted and hurt were one to
suggest that he is simply a writer and
thinker of the public domain. He believes that he can straddle successfully
the public and the professional, and would argue that as a professional
evolutionist he is indeed making frontline advances. We shall have to
consider this point. So for the moment, let us turn in a neutral fashion to
Gould's work.
Gould began his career in the mid-ig6os as a
paleontologist specializing in the evolution of snails (Gould 1969). At
this point, he was an orthodox Darwinian, who had written a review paper
on problems of relative growth (a sometime interest of Julian Huxley, whose
significance was acknowledged) showing how things considered nonadaptive
can be fitted readily into a selectionist framework (Gould 1966). Soon,
however, Gould was moving to make his own mark, most particularly with a
fellow paleontologist, Niles Eldredge, in advocating a new paleontological
theory of punctuated equilibria.
Together, Eldredge and Gould (1972) argued that the
traditional synthetic theorist's vision of evolution as a smooth, gradual
process, hidden only because of the incompleteness of the fossil record,
is quite mistaken. The fossil record is not so very inadequate, and in any
case there is theoretical reason to think that evolution will be jerky
rather than smooth. "If new species arise very rapidly in small,
peripherally isolated local populations, then the great expectation of
insensibly graded fossil sequences is a chimera. A new species does not
evolve in the area of its ancestors; it does not arise from the slow
transformation of all its forebears." Hence, "The history of life is more
adequately represented by a picture of 'punctuated equilibria' than by
the notion of phyletic gradualism. The history of evolution is not one of
stately unfolding, but a story of equilibria, disturbed only 'rarely'
(i.e., rather often in the fullness of time) by rapid and episodic events
of speciation" (84).
To make this case, Eldredge and Gould turned to the
writings of Ernst Mayr (1959, 1963), who had proposed the so-called
founder principle to explain speciation: a small group of organisms gets
isolated; because of variation within the parent population, the group
will have only a subselection of the total possible gene combinations;
this will cause a rapid "shaking down" or "genetic revolution" among the
members of the group as they learn to do with much less than the full
complement; and so there will be rapid evolution to new forms.
I am not sure how far one would want to say that any
of this was orthodoxly Darwinian. The founder principle seems to owe as
much to Wright's notion of drift as to anything in the Origin.
(Wright claimed it owed everything to his notion of drift.) Moreover,
with the emphasis on speciation rather than adaptation, Eldredge and
Gould were starting to think of life's histories less at the individual
level and more at the group level—where overall patterns were to be
understood through the dynamics of the arrival and disappearance of
groups (what another evolutionist was to label species selection). But
the general discussion was certainly placed in a Darwinian context, and
at this point (1972) Gould was not setting himself up as a critic of the
synthetic theory. He was merely arguing that people had not interpreted
that theory properly when it came to macroevolutionary changes as shown
by the fossil record.
However, as the 1970s rolled along, Gould started to
get more and more uneasy with conventional Darwinism, especially with
the assumption of ubiquitous adaptation. The main spur to skepticism
undoubtedly was a massive reading program in the history of evolutionary
thought that engaged Gould in preparation for a work he published in the
same year (1977) as Ever Since Darwin. This book, Ontogeny and
Phylogeny, part history, part science, argued that the much-despised
connections between ontogeny (the course of development of an individual
organism), especially in the embryonic stages, and phylogeny (the
evolutionary development of a species) still have some worth; and in
support he argued not only from evidence today but from the evidence of
history. Since this history inevitably involved a great deal of German
history, where the ontogeny/phylogeny analogy was taken most seriously,
Gould immersed himself in that morphological tradition which had so
infuriated Cuvier, Naturphilosophie: a holistic philosophy
stressing that the most significant features of organic life are the
isomorphisms which link organism to organism. Adaptation is in many
cases secondary or nonexistent, and unity of type or Bauplan (to
use the German term for organic groundplans or archetypes) is primary
(Russell 1916).
This led Gould to write numerous articles hostile to
ubiquitous adaptationism, including a celebrated
attack coauthored with the population geneticist
Richard Lewontin, in which attention was drawn to the nonfunctional
parts of the tops of church columns (which he called "spandrels";
see figure), and the moral was
drawn for organisms (Gould and Lewontin 1979). By 1980 Gould was ready
for an all-out assault on adaptationism, and he declared the synthetic
theory of evolution to be effectively dead. Gould's version of punctuated
equilibria (Eldredge has always remained more orthodoxly Darwinian) was
now edging close to saltations—macro-mutations—for those
crucial rapid changes in the course of evolutionary history (Gould
1980a).
Moves of this nature did not find favor with more
conventional Darwinians, especially those working experimentally on
rapidly reproducing organisms where natural selection is a vital tool.
It was pointed out that saltations have no empirical foundation and
that, on macro-scales, selection can do just about anything that you
could want (Stebbins and Ayala 1981). Although hardly acknowledged
formally, we see a consequent rapid
retreat by Gould to a position that is certainly not inconsistent
with Darwinian selection. However, it is not a retreat to the original
position. Now Gould (1982a) was (and would still claim to be) offering
an "expanded" Darwinism. Natural selection and adaptation are
undoubtedly important when one is considering organisms in their
day-to-day life and microevolution. But as one looks at more long-term
matters, one sees that other factors, including brute chance, come
increasingly into play.
Instead of the unilevel synthetic theory, one now
has a hierarchical theory, that is to say something (like the Catholic
Church) with different levels. Down at the lowest level (the
micro-level)—the level of immediate or short-term change—one
has a Dobzhansky kind of evolution that is essentially a function of
the genes under the control of natural selection and like processes.
But then one has upper levels (the macro-levels), where one is
thinking of evolution over long periods of time. Here one has
different processes at work. This means that no one level (especially
not the micro-level) is to be privileged (Gould 1982b). In the language
often used in such cases, the upper levels cannot be "reduced" to the
lower level, meaning (contra Dobzhansky) one cannot hope, to explain
away everything at the upper, bigger levels by expressing them in
terms of the lower, smaller level.
[ Michael Ruse,
Mystery of
Mysteries: Is Evolution a Social Construction, Cambridge, MA: Harvard
University Press, 1999, pp. 135-138. ]
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