Disproving evolution
From RationalWiki
There are many ways of disproving evolution.
Creationists and others sometimes claim that evolution and common descent cannot be falsified and consequently are not science.[1] This, however, is simply not the case.
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[edit] What would falsify evolution?
We all know that a characteristic of science is that it must be falsifiable, this feature of a theory is attributed to Karl Popper, who mentioned it in a criticism of darwinism.[2] Scientific theories cannot be proved outright – they can only fail to be disproved. This is because if something cannot be disproved, such as with Russell's Teapot, it makes no difference either way.
Evolution is based on three principles: variation, heritability and selection; if any of these were shown to be flawed then the theory would be untenable. Consequently any of the following would destroy the theory:
- If it could be proven that mutations do not occur.
- If it could be proven that, although mutations do occur, they are not passed down through the generations.
- If it could be proven that, although mutations are passed down, no mutation could produce the sort of phenotypic changes that drive natural selection.
- If it could be shown that selection or environmental pressures do not favor the reproductive success of better adapted individuals.
Darwin made the case a little differently when he said, "If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case." [3]
[edit] What would falsify common descent?
Common descent is the theory that all life evolved from one common ancestor, or groups of ancestors (although it is slightly more complicated than the straw man version of "one day a cell appeared and everything is technically its descendent"). Morphological and, more recently, genetic evidence puts common descent pretty close to being outright proven, but there are still ways to falsify it. Common descent could easily be disproved (without even seriously challenging the theory of evolution) if we discovered a form of life that was not related to all the life we know - most simply, by finding life that does not use the nucleic acids (DNA and RNA) for information storage and retrieval as known biological life does. This would be exemplified in the situation of a second genesis, where two different forms of life began at two completely different points.
Also, if we were ever to discover life elsewhere in the universe, the odds lean towards it not having a common ancestor with life on earth. This would really only require that "common descent" be modified to "life on earth", and similarly, the second genesis on Earth would signify that two forms have two common descents.
[edit] What about a precambrian rabbit?
J.B.S. Haldane famously stated that "fossil rabbits in the precambrian" would disprove evolution - and this has been a talking point in philosophy of science for some time. This phrase is reported to be a rebuttal to the accusations that evolution is not falsifiable. However, the reality of disproving evolution in this manner is quite complicated, such a thing wouldn't cause scientists to throw the theory out completely and immediately, so a little more explanation is needed.
First of all it must be remembered that the fossil record is supporting evidence for evolution. If the fossil record simply did not exist, that would make no difference to the validity of the theory of evolution. The simple truth is that a single strange fossil would probably not make much difference. In practice, the evidence in the fossil record which supports evolution is so overwhelming that a single fossil would be regarded as curious certainly, but compared to the mountain of evidence in favor of evolution it would probably be regarded as an anomaly while more data was awaited.
However, the existence of entire groups of anomalous fossils would be a different thing - Haldane did say rabbits after all. Again, in practice an effort would initially be made to fit the new data into the existing framework - this is not cheating but simply the way that science works. But still, in principle some quite major revisions to the theory may be needed to explain them. Such a situation would not immediately and conclusively prove a special creation over a naturalistic evolution, however, a key point that creation proponents tend to overlook.
If problems were found in general relativity, for instance, scientists would first see if the theory could be adapted to include the new data, if it could not then a new hypothesis would have to be formed which would go through the normal scientific testing process. The same thing would happen to our descriptions of the fossil record. Perhaps this anomalous group was due to a now extinct second genesis, which would be a remarkable find, but unlikely to disprove evolution outright.
What would happen if the entire fossil record were shown to have been faked, or if a vast number of fossils were found which could not be fit into the current schemes? In this rather contrived and hugely hypothetical case, there would be a contradiction of evidence which would have to be resolved. The scientific method would have to be used to resolve it.
[edit] Footnotes
- ↑ Falsifiability of evolution at Conservapedia
- ↑ Wikipedia on Karl Popper
- ↑ Origin of Species
