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According to Karl Popper's falsification criterion only a falsifiable theory is said to be a scientific theory. If this is true, is Evolution Theory falsifiable and hence considered scientific?

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Following on from @Conifold's answer. I think we need to distinguish between the falsifiability of evolution and the falsifiability of evolution by natural selection i.e. Darwinism.

Falsifying evolution would be trivially easy using the Jurassic bunny argument. In other words, if one was to discover a modern day mammal in the fossil record of 100mm years ago, say, it'd be a pretty big kick in the teeth for evolution. The fact that huge quantities of fossils have been found without any serious discrepancies is strong evidence for evolution.

Whether a particular trait occurred via natural selection or not, however, is harder to prove in general. Some are fairly obvious e.g. a genetic variant that caused a substantial increase in mortality prior to fertility is likely to lead to a genetic dead end pretty quickly. Others, such as eye colour, less so. In fact, there's probably a perfectly good argument that evolution of blue/brown/green eye colour is just a function of dominance rather than selection per se.

  • thanks for drawing the line between evolution and natural selection. It's an important point. Evolution is easily falsifiable, indeed. Seems like the evidence you suggest to falsify natural selection works as well. thanks! – Amit Hagin Jun 19 '15 at 15:22
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Here is Popper's famous quote from 1976 that caused the controversy:"I have always been extremely interested in the theory of evolution and very ready to accept evolution as a fact... 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". However, it is not as bad as it looks. His reference to Darwinism here concerns "survival of the fittest" with no testable way to determine the fittest other than to look at the survivors after the fact. In other words, "survival of the fittest" is "almost tautological" and unfalsifiable. Thus, "there exists no law of evolution, only the historical fact that plants and animals change, or more precisely, that they have changed".

Even so, Popper changed his mind two years later:"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... 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... I have changed my mind about the testability and logical status of the theory of natural selection; and I am glad to have an opportunity to make a recantation... The theory of natural selection may be so formulated that it is far from tautological. In this case it is not only testable, but it turns out to be not strictly universally true".

A good account is Sonleitner's What Did Karl Popper Really Say About Evolution?

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Of course it is falsifiable. Consider that we are living at the (current) end of an experiment that has been running for hundreds of millions of years. Evolution Theory lets us make predictions about outcomes, and these predictions can be verified. If the predictions were wrong, they could have been falsified.

  • I'm not sure this contains enough detail to convincingly answer the question. You pretty much just say "yes it can", without evidence or examples. – Rex Kerr Jun 19 '15 at 7:05
  • I agree with you Rex Kerr. Seems like the problem of evolution theory is that it has a great explanatory power while it presents a very weak power to predict. Therefore it will be very difficult to conceive of an empirical evidence (even potential) that might be unexplainable by some speculative evolutionary "excuse". Seems like Alex might have come up with one - a very obvious, indeed, but it seems like one of the only solutions to the problem. In any case, in does make Natural Selection Theory scientific according to the criterion. – Amit Hagin Jun 19 '15 at 15:18

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