Kiistikö Popper evoluution falsifioitavuuden?
"I do not see how, without it, our knowledge could have grown as it has done since Darwin. In trying to explain experiments with bacteria which become adapted to, say, penicillin, it is quite clear that we are greatly helped by the theory of natural selection. Although it is metaphysical, it sheds much light upon very concrete and very practical researches. It allows us to study adaptation to a new environment (such as a penicillin-infested environment) in a rational way: 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."
(Popper, "Unended Quest: An Intellectual Autobiography" 1976, 171-172)
Esimerkiksi Kranz ja Russell ovat ilmaisseet artikkelissaan Karl Popper's challenge"a, että Popper on kiistänyt evoluution falsifioitavuuden ja tätä kautta sen tieteellisyyden. He ovat oikeassa siinä, että Popper sanoi vuonna 1976 kirjoittamassaan kirjassa "Unended Quest: An Intellectual Autobiography", sivulla 151, että Darwinismi ei olisi testattava teoria vaan metafyysinen tutkimusohjelma.
Kuitenkin Popperin eifalsifioitavuusväite koski sitä, että luonnonvalintaa voitiin testata mutta ei täydellisissä määrin. Hän jatkoi myös että luonnonvalinta oli käytännöllinen teoria. Popper painotti samassa kirjassa sivulla 172, että teismi oli selityksenä huonompi kuin tappion myöntäminen koska se väitti että lopullinen selitys olisi saavutettu. Tämä tarkoittaa sitä että teismi onnistui falsifioinnissaan vielä luonnonvalintaa huonommin.
Kenties huomionarvoisinta on kuitenkin se, että hän myöhemmin muutti mieltään ja sanoi teoksessaan "Natural selection and the emergence of mind" vuodelta 1978, että luonnonvalinta on testattavissa oleva teoria. Popper painotti kirjassaan Dialectica 32:344-246, että hän on korjannut kantaansa luonnonvalinnan teoriasta ja että hän oli iloinen että sai mahdollisuuden ilmoittaa kannanmuutoksestaan.
Popper kirjoitti myös artikkelin "Popper: good philosophy, bad science?", joka julkaistiin New Scientist -lehden numerossa Elokuussa 1980.(New Scientist 87(1215):611, 21 Aug. 1980.)
Tässä artikkelissa Popper kertoi että evoluution falsifioimattomuusväite oli hänen erehdyksensä, ja että historialliset tieteet ovat testattavia vaikka ne kuvaavatkin uniikkeja tapahtumia. Testaus onnistuu jos niistä voidaan johtaa testattavia ennusteita.
Alkuperäisessä muotoilussaan Popper ei siis aluksi ymmärtänyt mistä evoluutiossa oli kysymys, vaan muotoili sen väärin. Tästä väärinymmärryksestä syntyi kehäpäätelmä, jonka Popper luonnollisesti toi esiin. -ja jonka korjasi kun virhe tuli esiin.
Aiheeseen viitaten kannattaa lukaista myös seuraava lainaus:
"Natural Selection and Its Scientific Status"
"When speaking here of Darwinism, I shall speak always of today's theory - that is Darwin's own theory of natural selection supported by the Mendelian theory of heredity, by the theory of the mutation and recombination of genes in a gene pool, and by the decoded genetic code. This is an immensely impressive and powerful theory. The claim that it completely explains evolution is of course a bold claim, and very far from being established. All scientific theories are conjectures, even those that have successfully passed many severe and varied tests. The Mendelian underpinning of modern Darwinism has been well tested, and so has the theory of evolution which says that all terrestrial life has evolved from a few primitive unicellular organisms, possibly even from one single organism. However, Darwin's own most important contribution to the theory of evolution, his theory of natural selection, is difficult to test. There are some tests, even some experimental tests; and in some cases, such as the famous phenomenon known as 'industrial melanism', we can observe natural selection happening under our very eyes, as it were. Nevertheless, really severe tests of the theory of natural selection are hard to come by, much more so than tests of otherwise comparable theories in physics or chemistry. 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 most offspring leave most offspring. C. H. Waddington says somewhere (and he defends this view in other places) that 'Natural selection . . . turns out ... to be a tautology' ..4 However, he attributes at the same place to the theory an 'enormous power. ... of explanation'. Since the explanatory power of a tautology is obviously zero, something must be wrong here. Yet similar passages can be found in the works of such great Darwinists as Ronald Fisher, J. B. S. Haldane, and George Gaylord Simpson; and others. 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', 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 programme. 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 programme. 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."
(Miller, "Popper Selections", 1985, 241-243)