Does Evolution Meet
the Criterion of Falsifiability
Karl R. Popper, Federation Proceedings, American
Societies for Experimental Biology, Vol. 22, 1963, p. 964.
There is a difficulty with Darwinism. While Lamarkism appears to be not
only refutable but actually refuted (because the kind of acquired adaptations which
Lamarck envisaged do not appear to be hereditary), it is far from clear what we should
consider a possible refutation of the theory of natural selection. If, more especially, we
accept that statistical definition of fitness which defines fitness by actual survival,
then the survival of the fittest becomes tautological, and irrefutable.
Darwin's great achievement was this, I believe. He showed that what
appeared to be purposeful adaptation may be explained by some mechanism--such as, for
example, the mechanism of natural selection. This was a tremendous achievement. But once
it is shown that a mechanism of this kind is possible, we ought to try to construct
alternative mechanisms, and then try to find some crucial experiments to decide between
them, rather than foster the belief that the Darwinian mechanism is the only possible one.
Karl R. Popper, Unended Quest (Revised edition)
(Open Court Publishers, La Salle, Ill., 1976), p. 168.
...I have come to the conclusion that Darwinism is not a testable
scientific theory, but a metaphysical research programme--a possible framework
for testable scientific theories.
Ibid., pp. 171-172.
And yet, the theory is invaluable. ...it suggests the existence of a
mechanism of adaptation, and it allows us even to study in detail the mechanism at work.
And it is the only theory so far which does all that.
This is, of course, the reason why Darwinism has been almost universally
accepted. Its theory of adaptation was the first nontheistic one that was convincing; and
theism was worse than an open admission of failure, for it created the impression that an
ultimate explanation had been reached.
Now to the degree that Darwinism creates the same impression, it is not
so very much better than the theistic view of adaptation; it is therefore important to
show that Darwinism is not a scientific theory, but metaphysical. But its value for
science as a metaphysical research programme is very great, especially if it is admitted
that it may be criticized, and improved upon.
L.C. Birch and P.R. Ehrlich, "Evolutionary
History and Population Biology," Nature, Vol. 214, 22 April 1967, p. 349.
...to...attempt to investigate ecology and taxonomy through a series of
inferences about the past is to base these sciences on non-falsifiable hypotheses....All
that is accomplished by those who feel that evolutionary history is the only pertinent
aspect of population biology is a confusion of data and untestable hypotheses.
Ibid., p. 351.
...the phylogenetic speculation...about the relative times of divergence
of butterfly and plant groups, the past significance of secondary plant substances, and so
on--are of no help whatever in explaining present day ecology. They are a series of
unfalsifiable hypotheses. These hypotheses do not help us to understand the distribution
and abundance of plants and butterflies today, because they are not subject to testing.
Ibid., p. 352.
Our theory of evolution has become, as Popper described,
one which cannot be refuted by any possible observations. Every conceivable
observation can be
fitted into it. It is thus "outside of empirical science" but
not necessarily false. No one can think of ways in which to test it. Ideas,
either without basis or based
on a few laboratory experiments carried out in extremely simplified systems,
have attained currency far beyond their validity. They have become part
of an evolutionary dogma
accepted by most of us as part of our training.
Sir Peter Medawar in Mathematical Challenges to the
Darwinian Interpretation of Evolution (The Wistar Institute Press, Philadelphia,
1967), p. xi.
...Then, there are philosophical or methodological objections to
evolutionary theory. They have been very well voiced by Professor Karl Popper--that the
current neo-Darwinian Theory has the methodological defect of explaining too much. It is
too difficult to imagine or envisage an evolutionary episode which could not be explained
by the formulae of neo-Darwinism.
Sir Peter Medawar in Studies in the Philosophy of
Biology, F.J. Ayala and T. Dobzhansky, editors (University of California Press,
Berkeley, 1974), p. 363.
I should like to address some comments about this equally to Jacques
[Monod] and Doby [Dobzhansky]. It seems to me that there is a real methodological weakness
in the modern evolution theory for which Dobzhansky is largely responsible. It explains
too much. It has such an enormous experimental facility that one could hardly imagine
anything it could not explain. Now the danger of this is that it rules out any incentive
to inquire about any other possible mechanisms that could explain the observed facts. In
this sense, the evolution theory is like psychoanalysis. If any young man started off with
a starry look in his eye saying that he wanted to inquire into the mechanisms of evolution
I think he would be like the young research student you referred to, Jacques, who was
looking for working class enzymes in that theory. They would think he was mad. But there
is a point there. Can you actually test (you can in microorganisms of course)--can you
test this kind of theory? It is very difficult to test it, say disprove it, or even having
the possibility of disproving in higher organisms the kind of evolution theory that you,
Dobzhansky, have done so much to establish.
Jacques Monod, ibid., p. 363.
Well, I think, Peter, that I agree with you that the explanatory power
of modern evolution theory is very great. In other words, it has the weakness of not being
highly vulnerable to experiment. But the reason it is not very vulnerable to experiment is
not because of the structure of the theory itself but because of the kinds of experiments
that would have to be done to falsify it. You see, according to Popper's criterion--and
again, correct me if I am wrong, Sir Karl--the theory falls on the right side of the
criterion, provided its structure is such that an experiment, including imaginary
experiments, could be done to falsify it. Whether an experiment can actually be done or
not is another matter. So it seems to me that as far as being falsifiable in principle the
modern theory of evolution is falsifiable. That it is extraordinarily difficult to put it
to actual experimental test, as opposed to observational test, is of course due to the
immense amounts of time involved....
C.H. Waddington, "Evolutionary Adaptation," in Evolution After Darwin, Vol. 1, Sol Tax, Editor (University of Chicago Press,
1960), pp. 385-386.
...Natural selection, which was at first considered as though it were a
hypothesis that was in need of experimental or observational confirmation, turns out on
closer inspection to be a tautology, a statement of an inevitable although previously
unrecognized relation. It states that the fittest individuals in a population (defined as
those which leave most offspring) will leave the most offspring. Once the statement is
made, its truth is apparent. This fact in no way reduces the magnitude of Darwin's
achievement; only after it was clearly formulated, could biologists realize the enormous
power of the principle as a weapon of explanation....
This explanation is a very powerful one. It could, in fact, explain
Bruce Wallace, Chromosomes, Giant Molecules and
Evolution (W.W. Norton & Co., Inc., New York, 1966), p. 5.
....Furthermore, we reject special creation as an adequate explanation
because we can think of no means by which we can put it to a valid test, because we can
imagine no observation falling outside the capabilities of a creator possessing unlimited
ability. Search diligently for the adequate, reject the untestable--these are the
recognized procedures of the laboratory, the classroom, the clinic, and the courtroom.
Ibid., p. 77.
...Rejecting as we must the untestable `explanation' of the origin of
species through special creation....
Ernst Mayr, Mathematical Challenges to the
Neo-Darwinian Interpretation of Evolution (Wistar Institute Press, Philadelphia,
1967), p. 47.
...most of this research dealt only with two factors, mutation and
selection, in other words, the original Darwinian model. Popper is right; this model is so
good that it can explain everything, as Popper has rightly complained.
Alex Fraser, ibid., p. 67.
...the only thing I have clearly agreed with through the whole day has
been the statement made by Karl Popper, namely, that the real inadequacy of evolution,
esthetically and scientifically, is that you can explain anything you want by changing
your variables around.
Murray Eden, ibid., p. 71.
...This[i.e., experimental falsification of the theory--editor] cannot
be done in evolution, taking it in its broad sense....It can, indeed, explain anything.
You may be ingenious in proposing a mechanism which looks plausible to human beings and
mechanisms which are consistent with other mechanisms which you have discovered, but it is
still an unfalsifiable theory.
Everett C. Olson, Evolution After Darwin, Vol.
1, Sol Tax, editor (University of Chicago Press, 1960), p. 530.
Selection theory, to date, has been the most successful
integrating concept that has been advanced. That no organic event has
been discovered that cannot be
explained by the "synthetic theory," or selection theory, as is often stated, is
in a sense true. On the other hand, the feeling of a slight sense of frustration in the
elasticity involved in developing a universal explanation is hard to avoid, a feeling
somewhat in sympathy with V. Bertalanffy when he noted "a lover of
paradox could say that the main objection to selection theory is that it
cannot be disproved."
...The origins of these structures are often "explained" by
abstract models that derive their principal data from "laws" of genetics,
"laws" which may be under dispute by the geneticists themselves. The extent of
assumption, interactions of assumptions, and the degrees of extrapolation give a sense of
uneasiness when the animals and their structures are foremost in mind. Essentially, the
student is faced with the following proposition: Given that certain "laws" of
genetics are correct, a particular event or series of events must have taken place to
produce a structure, if it be assumed that some particular set of conditions held during
the course of production. Many genetic models, however, as Lerner has noted, go well
beyond the evidence. they may not be trustworthy bases for the proposition. In the most
given situations, however, some of the conditions that held during development can be
deduced, even in paleontological studies, and there is good evidence that many of the
genetic "laws" hold, at least over a small part of the organic
world. But in most cases, detailed steps of development and details of
the environment in which they
took place are largely unknown. Thus, in explanation, it is usually true
that we end up with several possible courses to the same end and that it
is virtually impossible to
choose between the several intelligently. In this sense, there is little
or nothing that cannot explained under the selection theory, and, at present
this theory appears to be
unique in this respect.
Ibid., p. 531.
...It is not sufficient to show that something could have happened
otherwise, but rather that it could not have happened under the formulation that is the
synthetic theory. This is indeed difficult, and, for all the suspicions that some
paleontologists and morphologists may have about the adequacy of the theory, there is very
little that they can do to confirm these feelings on the basis of the types of analysis
that their materials allow. This may be further generalized, to the effect that there is
no known way of attacking experimentally some of the areas in which doubts of the
sufficiency of the synthetic theory arise--areas, for example, not subject to analysis
because of the time factor.
Ibid., pp. 535-537.
...The paleontologist...deals with morphology and sees
order in its change. He witnesses major trends...He sees what appear
to be highly adaptive types of
organisms side by side with what appear to be adaptive "monstrosities." He sees
groups of organisms, apparently in their prime, fade and disappear through
"short" periods. And he may ask: "All this through shift in gene
frequencies, in genetic shift through differential reproduction and slow change through
successive populations?" Even though he may answer Yes, there still
exists for many a feeling of remoteness between the concepts of evolution
seen in the elegant genetic
constructions of such students as Wright and Fisher and the equally penetrating
considerations of morphology and evolution as displayed by paleontologists
such as Romer, Watson, or Westoll. The efforts to bridge the gap leave
a real feeling of remoteness at
the operational level and in many cases a feeling that the explanations
of genetics and selection are not significantly applicable to some of the
types of phenomena observed in
much of the fossil record.
...The point has been made that the very conciseness, consistency, and
tightness of the synthetic theory, combined with the almost limitless flexibility due to
the nature of the definition of selection, can lead to acceptance of generalizations not
applicable over the whole range of evolution. This possible danger is amply revealed in
some studies of the last decade which seem more concerned with fitting results into the
current theory than with evaluation of results in terms of a broader outlook. Further, of
course, much research is conceived and carried out within the framework of the theory,
and, no matter what its excellence, it is not likely to break out of this framework....
...the important element of testing by experimentation
is not possible with fossil materials. The fossil record, on the other
hand, has been a source of data
that have been considered by various students as somewhat contrary to the
concepts developed in genetics and related fields and this in itself
can be an important
contribution. This evidence has been "explained" to the satisfaction
of many, although not all. ...
John C. Fentress in Mathematical Challenges to the
Neo-Darwinian Interpretation of Evolution (Wistar Institute Press, Philadelphia,
1967), p. 71.
...I would simply like to give one example which I think illustrates how
important it is to ask a precise question. When I was in Cambridge, we were working with
two species of British vole.
We had a little test in which an object moved overhead; one species
would freeze. Also, one species happened to live in the field. This was rather fun, and,
not really being a zoologist, I went up to see some of my zoologist friends and I reversed
the data. I asked them, simply, why a species which lived in the field should freeze and
why one that lived in the woods should run away (when the reverse was the case). I wish I
had recorded their explanations, because they were very impressive indeed.