To: curt@cdeckert.com
Subject: F.Y.I.: "A Scientific
Scandal"
Sent: Friday, May 09, 2003
From: K. Pennock [mailto:pennockk@discovery.org]
A Scientific Scandal
by David Berlinski
from Commentary Magazine, April,
2003
In science, as in life, it
is always an excellent idea to cut the cards after the deck has been shuffled.
One may admire the dealer, but trust is another matter.
In a recent
essay in Commentary, "Has Darwin Met His Match?" (December 2002), I discussed,
evaluated, and criticized theories of intelligent design, which have presented
the latest challenge to Darwin's theory of evolution. In the course of
the discussion I observed that the evolution of the mammalian eye has always
seemed difficult to imagine. It is an issue that Darwin himself raised,
and although he settled the matter to his own satisfaction, biologists
have long wished for a direct demonstration that something like a functional
eye could be formed in reasonable periods of time by means of the Darwinian
principles of random variation and natural selection.
Just such a demonstration,
I noted in my essay, is what the biologists Dan-Erik Nilsson and Susanne
Pelger seemed to provide in a 1994 paper.' Given nothing more than time
and chance, a "light-sensitive patch," they affirmed, can "gradually turn
into a focused-lens eye," and in the space of only a few hundred thousand
years——a mere moment, as such things go.
Nilsson and Pelger's
paper has, for understandable reasons, been widely circulated and widely
praised, and in the literature of evolutionary biology it is now regularly
cited as definitive. Not the least of its remarkable authority is derived
from the belief that it contains, in the words of one of its defenders,
a "computer simulation of the eye's evolution."
If this were true,
it would provide an extremely important defense of Darwin's theory. Although
a computer simulation is not by itself conclusive——a simulation is one
thing, reality another——it is often an important link in an inferential
chain. In the case of Darwin's theory, the matter is especially pressing
since in the nature of things the theory cannot be confirmed over geological
time by any experimental procedure, and it has proved very difficult to
confirm under laboratory conditions. The claim that the eye's evolution
has been successfully simulated by means of Darwinian principles, with
results falling well within time scales required by the theory, is thus
a matter of exceptional scientific importance.
And not just scientific
importance, I might add; so dramatic a confirmation of Darwinian theory
carries large implications for our understanding of the human species and
its origins. This is no doubt why the story of Nilsson and Pelger's computer
simulation has spread throughout the world. Their study has been cited
in essays, textbooks, and popular treatments of Darwinism like River Out
of Eden by the famous Oxford evolutionist Richard Dawkins; accounts of
it have made their way onto the Internet in several languages; it has been
promoted to the status of a certainty and reported as fact in the press,
where it is inevitably used to champion and vindicate Darwin's theory of
evolution.
In my essay, I suggested
that Nilsson and Pelger's arguments are trivial and their conclusions unsubstantiated.
I also claimed that representations of their paper by the scientific community
have involved a serious, indeed a flagrant, distortion of their work. But
in a letter published in the March issue of Commentary, the physicist Matt
Young, whom I singled out for criticism (and whose words I have quoted
here), repeated and defended his characterization of Nilsson and Pelger's
work as a "computer simulation of the eye's evolution." It is therefore
necessary to set the matter straight in some detail.
I hope this exercise
will help to reveal, with a certain uncomfortable clarity, just how scientific
orthodoxy works, and how it imposes its opinions on the faithful.
Here in their
own words is the main argument of Nilsson and Pelger's paper:
Theoretical considerations
of eye design allow us to find routes along which the optical structure
of the eye may have evolved. If selection constantly favors an increase
in the amount of detectable spatial information, a light-sensitive patch
will gradually turn into a focused-lens eye through continuous small improvements
in design. An upper limit for the number of generations required for the
complete transformation can be calculated with a minimum number of assumptions.
Even with a consistently pessimistic approach, the time required becomes
amazingly short: only a few hundred thousand years.
And here is how they
arrived at their conclusions. The setting is "a single circular patch of
light-sensitive cells"——a retina, in effect——"which is bracketed and surrounded
by dark pigment." A "protective layer" lies above these light-sensitive
cells, so that the pigment, the light-sensitive cells, and the protective
layer form a kind of sandwich. Concerning the light-sensitive patch itself;
Nilsson and Pelger provide no further details, indicating neither its size
nor the number of cells it might contain.
What they do assume,
if only implicitly, is that changes to the initial patch involve either
a deformation of its shape or a thickening of its cells. The patch can
be stretched, dimpled, and pulled or pushed around, and cells may move
closer to one another, like bond salesmen converging on a customer.
So much for what changes.
What is the change worth? Assuming (reasonably enough) that an eye is an
organ used in order to see, Nilsson and Pelger represent its value to an
organism by a single quantitative character or function, which they designate
as "spatial resolution" or "visual acuity"—— sharp sight, in short. Visual
acuity confers an advantage on an organism, and so, in any generation,
natural selection "constantly favors an increase in the amount of detectable
spatial information.
There are two ways
in which visual acuity may be increased in an initial light-sensitive patch:
a) by the "invagination" of the patch, so that it becomes progressively
more concave and eventually forms the enclosed interior of a sphere; and
b) by the constriction of the sphere's aperture (the two rounded boundaries
formed as the flat patch undergoes invagination). These changes may be
represented on sheets of high-school graph paper on which two straight
lines——the x and y axes of the system——have been crossed. On the first
sheet, representing invagination, visual acuity moves upward on one axis
as invagination moves to the right on the other; on the second sheet, visual
acuity moves upward as constriction moves to the right. The curves that
result, Nilsson and Pelger assert, are continuous and increasing. They
do not hurdle over any gaps, and they go steadily upward until they reach
a theoretical maximum.
The similar shape
of the two graphs notwithstanding, invagination and aperture constriction
exercise different effects on visual acuity. "Initially, deepening of the
pit"——i.e., invagination——"is by far the most efficient strategy," Nilsson
and Pelger write; "but when the pit depth equals the width, aperture constriction
becomes more efficient than continued deepening of the pit." From this,
they conclude that natural selection would act "first to favor depression
and invagination of the light-sensitive patch, and then gradually change
to favor constriction of the aperture."
The result is a pin-hole
eye, which is surely an improvement on no eye at all. But there exists
an aperture size beyond which visual acuity cannot be improved without
the introduction of a lens. Having done all that it can do, the pin-hole
eye lapses. Cells within the light-sensitive sphere now obligingly begin
to thicken themselves, bringing about a "local increase" in the eye's refractive
index and so forming a lens. When the focal length of the lens is 2.55
times its radius——the so-called Mattiessen ratio——the eye will have achieved,
Nilsson and Pelger write, the "ideal solution for a graded-index lens with
a central refractive index of 1.52."2
Thereafter, the lens "changes
its shape from ellipsoid to spherical and moves to the center of curvature
of the retina." A flat iris "gradually forms by stretching of the original
aperture," while the "focal length of the lens . . . gradually shortens,
[until] it equals the distance to the retina . . . producing a sharply
focused image." The appearance of this spherical, graded-index lens, when
placed in the center of curvature of the retina, produces "virtually aberration-free
imaging over the full 180 degrees of the visual field."
The same assumptions
that governed invagination and aperture constriction hold sway here as
well. Plotted against increasing lens formation, visual acuity moves smoothly
and steadily upward as a graded-index lens makes its appearance, changes
its shape, and moves to center stage. When these transformations have been
completed, the result is a "focused camera-type eye with the geometry typical
for aquatic animals."
One step remains.
Nilsson and Pelger now amalgamate invagination, constriction, and lens
formation into a single "transformation," which they represent by juxtaposing,
against changes in visual acuity, changes to the original patch in increments
of 1 percent. The resulting curve, specifying quantitatively how much visual
acuity may be purchased for each 1-percent unit of change, is ascending,
increasing, and straight, rising like an arrow at an angle of roughly 45
degrees from its point of origin. Transformations are "optimal" in the
sense that they bring about as much visual acuity as theoretically possible,
with the "geometry of each stage [setting] an upper limit to the spatial
resolution of the eye.
It is the existence
and shape of this fourth curve that justify their claim that "a light-sensitive
patch will gradually turn into a focused-lens eye through continuous small
improvements in design" (emphasis added). This is not the happiest formulation
they could have chosen.
How much does
the initial light-sensitive patch have to change in order to realize a
focused camera-type eye? And how long will it take to do so? These are
the questions now before us.
As I have mentioned,
Nilsson and Pelger assume that their initial light-sensitive patch changes
in 1-percent steps. They illustrate the procedure with the example of a
flat one-foot ruler that also changes in 1-percent steps. After the first
step, the ruler will be one foot plus 1 percent of one foot long; after
the second step, it will be 1-percent longer than the length just achieved;
and so forth. It requires roughly 70 steps to double a one-foot ruler in
length. Putting the matter into symbols, 1.0170
approximately equal 2.
Nilsson and Pelger
undertake a very similar calculation with respect to their initial light-sensitive
patch. But since the patch is a three-dimensional object, they are obliged
to deal with three dimensions of change. Growing in steps of 1 percent,
their blob increases its length, its curvature, and its volume. When all
of these changes are shoe-horned together, the patch will have increased
in magnitude along some overall (but unspecified) dimension.
The chief claim of
their paper now follows: to achieve the visual acuity that is characteristic
of a "focused camera-type eye with the geometry typical for aquatic animals,"
it is necessary that an initial patch be made 80,129,540 times larger (or
greater or grander) than it originally was. This number represents the
magnitude of the blob's increase in size. How many steps does that figure
represent? Since 80,129,540 = 1.011,829,
Nilsson and Pelger conclude that "altogether 1,829 steps of 1 percent are
required" to bring about the requisite transformation.
These steps, it is
important to remember, do not represent temporal intervals. We still
need to assess how rapidly the advantages represented by such a transformation
would spread in a population of organisms, and so answer the question of
how long the process takes. In order to do this, Nilsson and Pelger turn
to population genetics. The equation that follows involves the multiplication
of four numbers:
R = h2 x i x V x m
Here, R is the
response (i.e. visual acuity in each generation), h is the coefficient
of heredity, i designates the intensity of selection, V is
the coefficient of variation (the ratio of the standard deviation to the
mean), and m, the mean value for visual acuity. These four numbers
designate the extent to which heredity is responsible for visual acuity,
the intensity with which selection acts to prize it, the way its mean or
average value is spread over a population, and the mean or average value
itself. Values are assigned as estimates to the first three numbers; the
mean is left undetermined, rising through each generation.
As for the estimates
themselves, Nilsson and Pelger assume that h2
=.50; that i = 0.01; and that V = 0.01. On this basis, they
conclude that R=0.00005m. The response in each new generation
of light-sensitive patches is 0.00005 times the mean value of visual acuity
in the previous generation of light-sensitive patches.
Their overall estimate——the
conclusion of their paper——now follows in two stages. Assume that n represents
the number of generations required to transform a light-sensitive patch
into a "focused camera-type eye with the geometry typical for aquatic animals."
(In small aquatic animals, a generation is roughly a year.) If, as we have
seen, the mean value of visual acuity of such an eye is 1.011,829=
80,129,540, where 1,829 represents the number of steps required and 80,129,540
describes the extent of the change those steps bring about; and if 1.00005"=
1.011,829 = 80,129,540,
then it follows that n= 363,992. It is this figure——363,992——that allows
Nilsson and Pelger to conclude at last that "the time required [is] amazingly
short: only a few hundred thousand years." And this also completes my exposition
of Nilsson and Pelger's paper. Business before pleasure.
Nilsson and
Pelger's work is a critic's smorgasbord. Questions are free and there are
second helpings.
Every scientific paper
must begin somewhere. Nilsson and Pelger begin with their assumption that,
with respect to the eye, morphological change comes about by invagination,
aperture constriction, and lens formation. Specialists may wish to know
where those light-sensitive cells came from and why there are no other
biological structures coordinated with or contained within the interior
of the initial patch——for example, blood vessels, nerves, or bones. But
these issues may be sensibly deferred.
Not so the issues
that remain. Nilsson and Pelger treat a biological organ as a physical
system, one that is subject to the laws of theoretical optics. There is
nothing amiss in that. But while theoretical optics justifies a qualitative
relationship between visual acuity on the one hand and invagination, aperture
constriction, and lens formation on the other, the relationships that Nilsson
and Pelger specify are tightly quantitative. Numbers make an appearance
in each of their graphs: the result, it is claimed, of certain elaborate
calculations. But no details are given either in their paper or in its
bibliography. The calculations to which they allude remain out of sight,
if not out of mind.
The 1-percent steps:
in what units are they expressed? And how much biological change is represented
by each step? Nilsson and Pelger do not say. Nor do they coordinate morphological
change, which they treat as simple, with biochemical change, which in the
case of light sensitivity is known to be monstrously complex.
Does invagination
represent a process in which the patch changes as a whole, like a balloon
being dimpled, or is it the result of various local processes going off
independently as light-sensitive cells jostle with one another and change
their position? Are the original light-sensitive cells the complete package,
or are new light-sensitive cells added to the ensemble as time proceeds?
Do some cells lose their sensitivity and get out of the light-sensing business
altogether? We do not know, because Nilsson and Pelger do not say.
Biologists commenting
on Darwin's theory have almost always assumed that evolution reflects what
the French biologist Franççois Jacob called brico-lage——a
process of tinkering. Biological structures are put together out of pieces;
they adapt their function to changes in their circumstances; they get by.
This suggests that in the case of eye formation, morphological change might
well purchases less visual acuity than Nilsson and Pelger assume, the eye
being tinkered into existence instead of flogged up an adaptive peak. But
if, say, only half as much visual acuity is purchased for each of Nilsson
and Pelger's 1-percent steps, twice as many steps will be needed to achieve
the effect they claim. What is their justification for the remarkably strong
assertion that morphological transformations purchase an optimal amount
of visual acuity at each step?
Again we do not know,
because they do not say.
More questions——and
we have not even finished the hors d'oeuvres. The plausibility of Nilsson
and Pelger's paper rests on a single number: 1,829. But without knowing
precisely how the number 1,829 has been derived, the reader has no way
of determining whether it is reasonable or even meaningful.
If nothing else, the
number 1,829 represents the maximum point of a curve juxtaposing visual
acuity against morphological transformation. Now, a respect for the ordinary
mathematical decencies would suggest that the curve is derived from the
number, and the number from various calculations. But all such calculations
are missing from Nilsson and Pelger's paper. And if the calculations are
not given, neither are any data. Have Nilsson and Pelger, for example,
verified their estimate, either by showing that 1,829 1-percent steps do
suffice to transform a patch into an eye, or by showing that such an eye
may, in 1,829 1-percent steps, he resolved backward into an initial light-sensitive
patch? Once again, we do not know because they do not say.
Still other questions
suggest themselves. Although natural selection is mentioned by Nilsson
and Pelger, it is a force that plays no role in their reasoning. Beyond
saying that it "constantly favors an increase in the amount of detectable
spatial information," they say nothing at all. This is an ignominious omission
in a paper defending Darwinian principles. An improvement in visual acuity
is no doubt a fine thing for an organism; but no form of biological change
is without cost.
Let us agree that
in the development of an eye, an initial light-sensitive patch in a given
organism becomes invaginated over time. Such a change requires a corresponding
structural change to the organism's anatomy. If nothing else, the development
of an eye requires the formation of an eye socket—— hardly a minor matter
in biological terms. Is it really the case that an organism otherwise adapted
to its environment would discover that the costs involved in the reconstruction
of its skull are nicely balanced by what would initially be a very modest
improvement in sensitivity to light? I can imagine the argument going either
way, but surely an argument is needed.
Then there is Nilsson
and Pelger's data-free way with statistics. What is the basis of the mathematical
values chosen for the numbers they use in assessing how rapidly transformation
spreads in a population of eye patches? The coefficient of variation is
the ratio of the standard deviation to the mean. The standard deviation,
one might ask, of what? No population figures are given; there are no quantitative
estimates of any relevant numerical parameter. Why is selection pressure
held constant over the course of 300,000 years or so, when plainly the
advantages to an organism of increasing light sensitivity will change at
every step up the adaptive slope? Why do they call their estimates pessimistic
(that is, conservative) rather than wildly optimistic?
Finally, Nilsson and
Pelger offer an estimate of the number of steps, computed in 1-percent
(actually, 1.00005-percent) intervals, that are required to transform their
initial patch. At one point, they convert the steps into generations. But
a step is not a temporal unit, and, for all anyone knows, each step could
well require half again or twice the number of generations they suggest.
Why do Nilsson and Pelger match steps to generations in the way they do?
I have no idea, and they do not say.
We are at last
at the main course. Curiously enough, it is the intellectual demands imposed
by Darwin's theory of evolution that serve to empty Nilsson and Pelger's
claims of their remaining plausibility.
Nilsson and Pelger
assert that only 363,992 generations are required to generate an eye from
an initial light-sensitive patch. As I have already observed, the number
363,992 is derived from the number 80,129,540, which is derived from the
number 1,829——which in turn is derived from nothing at all. Never mind.
Let us accept 1,829 pour le sport. If Nilsson and Pelger intend their model
to be a vindication of Darwin's theory, then changes from one step to another
must be governed by random changes in the model's geometry, followed by
some mechanism standing in for natural selection. These are, after all,
the crucial features of any Darwinian theory. But in their paper there
is no mention whatsoever of randomly occurring changes, and natural
selection plays only a ceremonial role in their deliberations.
At the beginning of
their paper, Nilsson and Pelger write of their initial light-sensitive
patch that "we expose this structure to selection pressure favoring spatial
resolution" (emphasis added), and later that "[as the lens approaches focused
conditions, selection pressure gradually appears to ... adjust its size
to agree with Mattiesen's ratio" (emphasis added). But whatever Nilsson
and Pelger may have been doing to their patch, they have not been exposing
it to "selection pressure." The patch does only what they have told it
to do. By the same token, selection pressures play no role in adjusting
the size of their lenses to agree with Mattiesen's ratio. That agreement
is guaranteed, since it is Nilsson and Pelger who bring it about, drawing
the curve and establishing the relevant results. What Nilsson and Pelger
assume is that natural selection would track their results; but this assumption
is never defended in their paper, nor does it play the slightest role in
their theory.
And for an obvious
reason: if there are no random variations occurring in their initial light-sensitive
patch, then natural selection has nothing to do. And there are no random
variations in that patch, their model succeeding as a defense of Darwin's
theory only by first emptying the theory of its content.
An example may make
clearer both the point and its importance. Only two steps are required
to change the English word "at" to the English word "do": "at" to "ao"
and "ao" to "do." The changes are obvious: they have been designed to achieve
the specified effect. But such design is forbidden in Darwinian theory.
So let us say instead, as Darwin must, that letters are chosen randomly,
for instance by being fished from an urn. In that case, it will take, on
average, 676 changes (26 letters times 26) to bring about the same two
steps.
Similarly, depending
on assessments of probability, the number of changes required to bring
about a single step in Nilsson and Pelger's theory may range widely. It
may, in fact, be anything at all. How long would it take to transform a
light-sensitive patch into a fully functioning eye? It all depends. It
all depends on how likely each morphological change happens to he. If cells
in their initial light-sensitive patch must discover their appointed role
by chance, all estimates of the time required to bring about just the transformations
their theory demands——invagination, aperture construction, and lens formation——will
increase by orders of magnitude.
If Darwin were restored
to pride of place in Nilsson and Pelger's work, the brief moment involved
in their story would stretch on and on and on.
Finally, there
is the matter of Nilsson and Pelger's computer simulation, in many ways
the gravamen of my complaints and the dessert of this discussion.
A computer simulation
of an evolutionary process is not a mysterious matter. A theory is given,
most often in ordinary mathematical language. The theory's elements are
then mapped to elements that a computer can recognize, and its dynamical
laws, or laws of change, are replicated at a distance by a program. When
the computer has run the program, it has simulated the theory.
Although easy to grasp
as a concept, a computer simulation must meet certain nontrivial requirements.
The computer is a harsh taskmaster, and programming demands a degree of
specificity not ordinarily required of a mathematical theory. The great
virtue of a computer simulation is that if the set of objects is large,
and the probability distribution and fitness function complicated, the
computer is capable of illustrating the implications of the theory in a
way that would be impossible using ordinary methods of calculation. "Hand
calculations may he sufficient for very simple models," as Robert E. Keen
and James Spain write in their standard text, Computer Simulation in
Biology (1992), "but computer simulation is almost essential for understanding
multi-component models and their complex interrelationships."
Whatever the merits
of computer simulation, however, they are beside the point in assessing
Nilsson and Pelger's work. In its six pages, their paper contains no mention
of the words "computer" or "simulation." There are no footnotes indicating
that a computer simulation of their work exists, and their bibliography
makes no reference to any work containing such a simulation.
Curious about this
point, I wrote to Dan-Erik Nilsson in the late summer of 2001. "Dear David,"
he wrote back courteously and at once,
You are right that
my article with Pelger is not based on computer simulation of eye evolution.
I do not know of anyone else who [has] successfully tried to make such
a simulation either. But we are currently working on it. To make it behave
like real evolution is not a simple task. At present our model does produce
eyes gradually on the screen, but it does not look pretty, and the genetic
algorithms need a fair amount of work before the model will be useful.
But we are working on it, and it looks both promising and exciting.
These are explicit
words, and they are the words of the paper's senior author. I urge readers
to keep them in mind as we return to the luckless physicist Matt Young.
In my Commentary essay of last December, I quoted these remarks by Mr.
Young:
Creationists used
to argue that . . . there was not enough time for an eye to develop. A
com––puter simulation by Dan-Erik Nilsson and Su––sanne Pelger gave the
lie to that claim. These, too, are forthright words, but as I have just
shown, they are false: Nilsson and Pelger's paper contains no computer
simulation, and no computer simulation has been forthcoming from them in
all the years since its initial publication. Sheer carelessness, perhaps?
But now, in responding to my Commentary article, Matt Young has redoubled
his misreading and proportionately augmented his indignation. The full
text of his remarks appears in last month's Commentary; here are the relevant
passages:
In describing the
paper by Nilsson and Pelger……, I wrote that they had performed a computer
simulation of the development of the eye. I did not write, as Mr. Berlinski
suggests, that they used nothing more than random variation and natural
selection, and I know of no reference that says they did.
…….The paper by Nilsson
and Pelger is a sophisticated simulation that even includes quantum noise;
it is not, contrary to Mr. Berlinski's assertion, a back-of-the-envelope
calculation. It begins with a flat, light——sensitive patch, which they
allow to become concave in increments of 1 percent, calculating the visual
acuity along the way. When some other mechanism will improve acuity faster,
they allow, at various stages, the formation of a graded-index lens and
an iris, and then optimize the focus. Unless Nilsson and Pelger performed
the calculations in closed form or by hand, theirs was, as I wrote, a "computer
simulation." Computer——aided simulation might have been a slightly better
description, but not enough to justify Mr. Berlinski's sarcasm at my expense....
And here is my familiar
refrain: there is no simulation, "sophisticated" or otherwise, in Nilsson
and Pelger's paper, and their work rests on no such simulation; on this
point, Nilsson and I are in complete agreement. Moreover, Nilsson and Pelger
do not calculate the visual acuity of any structure, and certainly not
over the full 1,829 steps of their sequence. They suggest that various
calculations have been made, but they do not show how they were made or
tell us where they might be found. At the very best, they have made such
calculations for a handful of data points, and then joined those points
by a continuous curve.
There are two equations
in Nilsson and Pelger's paper, and neither requires a computer for its
solution; and there are no others. Using procedures very much like
Nilsson and Pelger's own, Mr. Young has nevertheless deduced the existence
of a missing computer simulation on theoretical grounds: "Unless Nilsson
and Pelger performed the calculations in closed form or by hand, theirs
was, as I wrote, a computer simulation." But another possibility at once
suggests itself: that Nilsson and Pelger did not require a computer simulation
to undertake their calculations because they made no such calculations,
their figure of 1,829 steps representing an overall guess based on the
known optical characteristics of existing aquatic eyes.
Whatever the truth——and
I do not know it——Mr. Young's inference is pointless. One judges a paper
by what it contains and one trusts an author by what he says. No doubt
Matt Young is correct to observe that "computer-aided simulation might
have been a better description" of Nilsson and Pelger's work. I suppose
one could say that had Dan-Erik Nilsson and Susanne Pelger rested their
heads on a computer console while trying to guess at the number of steps
involved in transforming a light-sensitive patch into a fully functioning
eyeball, their work could also be represented as computer-aided.
Matt Young is hardly
alone in his lavish misreadings. The mathematician Ian Stewart, who should
certainly know better, has made virtually the same patently false claims
in Nature's Numbers (1995). So have many other prominent figures.3
But misreadings are one thing, misrepresentations another. More than anyone
else, it has been Richard Dawkins who has been responsible for actively
misrepresenting Nilsson and Pelger's work, and for disseminating worldwide
the notion that it offers a triumphant vindication of Darwinian principles.
In a chapter of his
1995 book, River Out of Eden, Dawkins writes warmly and at length
about Nilsson and Pelger's research.4
Here is what he says (emphasis added throughout):
[Their] task was to
set up computer models of evolving eyes to answer two questions
. . . [:] is there a smooth gradient of change, from flat skin to full
camera eye, such that every inter-mediate is an improvement? . . . [and]
how long would the necessary quantity of evolutionary change take?
In their computer
models, Nilsson and Pelger made no attempt to simulate the internal
workings of cells.
…….Nilsson and Pelger
began with a flat retina atop a flat pigment layer and surmounted by a
flat, protective transparent layer. The transparent layer was allowed to
undergo
localized random mutations of its refractive index. They then let the
model transform itself at random, constrained only by the requirement
that any change must be small and must be an improvement on what went before.
The results were swift
and decisive. A trajectory of steadily mounting acuity led unhesitatingly
from the flat beginning through a shallow indentation to a steadily deepening
cup, as the shape of the model eye deformed itself on the computer screen
And then, almost like a conjuring trick, a portion of this transparent
filling condensed into a local, spherical region of higher refractive index.
…….This ratio is called
Mattiessen ‘‘s ratio. Nilsson and Pelger's computer——simulation model
homed in unerringly on Mattiessen's ratio.
How very remarkable
all this is——inasmuch as there are no computer models mentioned, cited,
or contained in Nilsson and Pelger's paper; inasmuch as Dan-Erik Nilsson
denies having based his work on any computer simulations; inasmuch as Nilsson
and Pelger never state that their task was to "set up computer models of
evolving eyes" for any reason whatsoever; inasmuch as Nilsson and Pelger
assume but do not prove the existence of "a smooth gradient of change,
from flat skin to full camera eye, such that every intermediate is an improvement";
and inasmuch as the original light-sensitive patch in Nilsson and Pelger's
paper was never allowed to undergo "localized random mutations of its refractive
index."
And how very remarkable
again——inasmuch as there are no computer "screens" mentioned or cited by
Nilsson and Pelger, no indication that their illustrations were computer-generated,
and no evidence that they ever provided anyone with a real-time simulation
of their paper where one could observe, "almost like a conjuring trick,"
the "swift and decisive" results of a process that they also happen to
have designed.
And yet again how
very remarkable——inasmuch as Nilsson and Pelger's "computer——simulation
model" did not home in unerringly on Mattiessen's ratio, Nilsson and Pelger
having done all the homing themselves and thus sparing their model the
trouble. Each and every one of these very remarkable asseverations can
be explained as the result of carelessness only if one first indicts their
author for gross incompetence.
Final questions. Why,
in the nine years since their work appeared, have Nilsson and Pelger never
dissociated themselves from claims about their work that they know are
unfounded? This may not exactly be dishonest, but it hardly elicits admiration.
More seriously, what of the various masters of indignation, those who are
usually so quick to denounce critics of Darwin's theory as carrying out
the devil's work? Eugenie Scott, Barbara Forrest, Lawrence Krauss, Robert
T Pennock, Philip Kitcher, Kelly Smith, Daniel Dennett, Paul Gross, Ken
Miller, Steven Pinker——they are all warm from combat. Why have they never
found reason to bring up the matter of the mammalian eye and the computer
simulation that does not exist?
And what should
we call such a state of affairs? I suggest that scientific fraud will do
as well as any other term.
DAVID BERLINSKI is the author
of A Tour of the Calculus, The Advent of the Algorithm, and
Newton's Gift. His new book, Secrets of the Vaulted Sky, is forthcoming
from Harcourt later this year.
1 "A Pessimistic Estimate of the
Time Required for an Eye to Evolve," Proceedings of the Royal Society,
London B (1994) 256, 53-58. In my essay I twice misspelled Susanne
Pelger's name, for which I apologize.
2 A graded——index lens is a lens
that is not optically homogeneous; the figure of 1.52 is "the value close
to the upper limit for biological material."
3 Among those who, by contrast,
have raised (on the Internet) points similar to my own, I would single
out especially Brian Harper, a professor of mechanical engineering at Ohio
State University.
4 A version of the same material
by Dawkins, "Where D'you Get Those Peepers," was published in the New
Statesman (July 16, 1995). |
- Contents
Click to Send E-Mail to
