After Williams and others had made the comment that fitness is a tautology, it came around that the point needed to be discussed in more detail. One such discussion was by a student of Dobzhansky’s, Richard Lewontin.
I would like at this point to destroy what I think is an error in the writings about evolutionary theory, an error at least from our modern standpoint. That is the problem of whether or not the principle of natural selection, or survival of the fittest, is an explanation of evolution. I maintain that it is not an explanation of evolution and it should not be intended as such, whatever the intent of Charles Darwin and his disciples may have been. Evolution is the necessary consequence of three observations about the world, observations which are at this moment unchallengeable. They are: (1) There is phenotypic variation; the members of a species do not all look and act alike. (2) There is a correlation between parents and offspring. This statement says nothing about Mendelism, nothing about genetics. It just says that if the two parents are shorter than the average, their children will on the average be shorter. That is an observation which is true for every character to a different degree, but for every character that can evolve, it must be true. (3) Different phenotypes leave different numbers of offspring in remote generations. (If they have more grandchildren, that’s good enough). If these three propositions are true, there will be an unavoidable evolutionary change in the population. Does that mean, then, that the principle of natural selection is an explanation of evolution?
These are three contingent statements, all of which are true about at least some part of the biological world, and it therefore follows that evolution must occur. The reason I list them is because there is a lot of confusion about the so-called “tautological” nature of the explanation of fitness and natural selection. There is nothing tautological here. These are three true statements about the world, and it follows from them that changes must occur in the population and that these changes can be predicted. If you like, these three statements are the explanation of evolution. They do not explain the origin of any particular event in evolution; they explain why there is a change, in general, in the forms of organisms in time. [Richard Lewontin 1969: 41-42]
Here Lewontin “debunks” the tautology argument in the traditional way; but it is still unclear enough to become a major philosophical, and later, popular creationist, argument “against” Darwin.
Slightly earlier, A. K. Manser had published a paper in which the tautology argument is fully formulated. In discussing the melanic moth example of Kettlewell, he writes:
The account itself is only a description in slightly theory-laden terms which gives the illusion of an explanation in the full scientific sense. If no mutant forms had occurred and the species had become extinct as a result of the change of circumstances, it would not have been adaptable. We cannot use the account to predict what will happen when a new feature occurs in the environment of a different species, or even if there is another change in the environment of the original moths. All we can do is, after there has been time for the state of affairs to become stable again, say whether the species in question was or was not adaptable. As had been pointed out, there can be no independent criterion of fitness or adaptability; survival and adaptability or fitness are necessarily connected.
Note that prediction appears here as a problem for evolution. He continues
As in the case of ‘adaptation’, other key terms of the theory, such as ‘variation’ and ‘environment’, suffer from circular definitions. [Manser 1965: 25f]
He also appeals to Popper:
As regards the latter, Professor Popper has said: ‘In most cases we have, before falsifying a hypothesis, another one up our sleeves; for the falsifying experiment is usually a crucial experiment designed to decide between the two. That is to say, it is suggested by the fact that the two hypotheses differ in some respect; and it makes use of this difference to refute (at least) one of them.’ … In the case of evolution there seems no particular direction to look for any tests because no testable alternative presents itself to us, nor has done since Darwin published his original work. Part of the difficulty here is that the circularity of the definitions of the key terms make it hard to see how alternative theories could be formulated, let alone tested. Theories which are not testable in any way are clearly ruled out. [p32f, bold emphasis mine]
Popper’s view of science plays a crucial role in this debate in the post-centennial period, as we can see.
Manser’s paper triggered a small flurry of responses (Barker 1969, Brady 1979, Tuomi 1981, Waters 1986).
Into this comes Karl Popper. Now Popper had already been applied to “Darwinian evolution” by K. K. Lee (1969), but concluded with the argument that since evolution was unfalsifiable there had to be something wrong with Popper, not Darwin, at a time when Popper’s view of science was being attacked by philosophers, especially in the light of Kuhn’s Revolutions (1962).
Popper’s first comment – the one that creationists love to quote – comes in, ironically, a text in which he’s trying to set up an evolutionary account of knowledge. He strikes all the right notes – it’s Spencer not Darwin, it’s only almost tautological (which is problematic, since a statement either is tautological or it isn’t), and it’s about “fitness”.
Quite apart from evolutionary philosophies, the trouble about evolutionary theory is its tautological, or almost tautological, character: the difficulty is that Darwinism and natural selection, though extremely important, explain evolution by “the survival of the fittest” (a term due to Herbert Spencer). Yet there does not seem to be much difference, if any, between the assertion “those that survive are the fittest” and the tautology “those that survive are those that survive”. For we have, I am afraid, no other criterion of fitness than actual survival, so that we conclude from the fact that some organisms have survived that they were the fittest, or those best adapted to the conditions of life. [Popper 1972: 241-242]
He expanded upon this later:
From this point of view the question of the scientific status of Darwinian theory – in the widest sense, the theory of trial and error-elimination – becomes an interesting one. 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 hypotheses. [Schilpp 1974: p134, also Popper 1976, p168 in the 2002 edition]
However, after several of his evolutionary biology aware friends, especially Donald Campbell, had taken him to task for this, he famously recanted:
The fact that the theory of natural selection is difficult to test has led some people, anti-Darwinists and even some great Darwinists, to claim that it is a tautology. A tautology like “all tables are tables” is not, of course, testable; nor has it any explanatory power. It is therefore most surprising to hear that some of the greatest contemporary Darwinists themselves formulate the theory in such a way that it amounts to the tautology that those organisms that leave the most offspring leave the most offspring. And C. H. Waddington even says somewhere (and he defends this view in other places) that “Natural selection … turns out … to be a tautology”.6 However, he attributes at the same place to the theory an “enormous power … of explanation”. Since the explanatory power is obviously zero, something must be wrong here.
I mention this problem because I too belong among the culprits. Influenced by what these authorities say, I have in the past described the theory as “almost tautological”,7 and I have tried to explain how the theory of natural selection could be untestable (as is a tautology) and yet of great scientific interest. My solution was that the doctrine of natural selection is a most successful metaphysical research program. It raises detailed problems in many fields, and it tells us what we would expect of an acceptable solution of these problems.
I still believe that natural selection works in this way as a research program. Nevertheless, I have changed my mind about the testability and the logical status of the theory of natural selection; and I am glad to have an opportunity to make a recantation. My recantation may, I hope, contribute a little to the understanding of the status of natural selection.
… not everything that evolves is useful, although it is astonishing how many things are; and … in conjecturing what is the use of an organ or behavioral program, we conjecture a possible explanation: of why it evolved in the way it has, and perhaps even of how it evolved. In other words, it seems to me that like so many theories in biology, evolution by natural selection is not strictly universal, though it seems to hold for a vast number of important cases.
6. C. H. Waddington, “Evolutionary Adaptation”, in S. Tax, ed., Evolution After Darwin: volume I – The Evolution of Life (Chicago: Chicago University Press, 1960) pp. 381-402; see p. 385.
7. Objective Knowledge (Oxford: Clarendon Press, 1972), p241. …
[Popper 1987: p143-145, also in Popper 1978]
At this point, Popper has accepted that it simply is not a tautology if it can sometimes be false, and it sometimes is. But the creationists did not read this, or ignored it if they did.
In the next post I will talk about two episodes in which the tautology problem arose in public discourse, via Bethell, Gould and Macbeth, before I go on to look at how it played out in the philosophy literature. Then I will look at what a tautology actually is, and what the problems are in general. My final post will discuss a resolution, which has, I trust, some deeper implications about scientific modelling and explanation.
Barker, A. D. 1969. An approach to the theory of natural selection. Philosophy 44 (170):271-290.
Brady, Ronald H. 1979. Natural Selection and the Criteria by which a Theory is Judged. Systematic Zoology 28 (4):600-621.
Kuhn, Thomas S. 1962. The structure of scientific revolutions, International encyclopedia of unified science; v. 2 no. 2. Chicago: University of Chicago Press.
Lee, K. K. 1969. Popper’s Falsifiability and Darwin’s Natural Selection. Philosophy 44 (170):291-302.
Lewontin, Richard C. 1969. The bases of conflict in biological explanation. Journal of the History of Biology 2 (1):35-45.]
Manser, A.R. 1965. The Concept of Evolution. Philosophy 40 (151):18-34.
Popper, Karl R. 1972. Objective knowledge; an evolutionary approach. Oxford: Clarendon Press.
Popper, Karl R. 1976. Unended quest: an intellectual autobiography. Revised ed. London: Fontana.
Popper, Karl. 1978. Natural Selection and the Emergence of Mind. Dialectica 32 (3-4):339-355.
Popper, Karl. 1987. “Natural Selection and the Emergence of Mind”. In Evolutionary epistemology, rationality, and the sociology of knowledge, edited by G. Radnitzky and W. W. B. III. La Salle, Ill.: Open Court:139-146.
Schilpp, Paul Arthur, ed. 1974. The philosophy of Karl Popper. La Salle, Ill.: Open Court.
Tuomi, Juha. 1981. Structure and Dynamics of Darwinian Evolutionary Theory. Systematic Zoology 30 (1):22-31.
Waters, C. Kenneth. 1986. Natural Selection Without Survival of the Fittest. Biology and Philosophy 1 (2):207-225.