This is a tricky question to answer impartially - as I'm sure you will agree.
One big issue is that it is difficult to conceive of any findings which would irrefutable falsify evolution. A major reason for this is the sheer weight of data supporting the theory. So if one piece of evidence arises which (seems) to challenge evolution, it would have to:
[1] withstand a huge amount of scrutiny, and
[2] outweigh the supporting evidence.
The "evolution" of scientific theories usually proceeds thus:
- hypothesis is proposed and tested
- evidence is found: if this evidence supports the hypothesis, then the hypothesis remains unchanged (and is further tested in subsequent experiment). If the evidence does not support the hypothesis, then the hypothesis is either rejected or modified
- if the hypothesis is rejected, then an alternative if often proposed, but this is not always the case!
So - with the example of precambrian rabbits, the fossil would naturally be subject to enormous interest. There have been several similar findings in the past - such as supposed sandal-prints alongside trilobites - and such findings have been explained without any recourse to rewriting or discarding evolution.
And, if the remains were found to be genuine, then the likely outcome is a re-writing of evolution to include precambrian lagomorphs (a "kneeding" of the data, as you put it). Of course, such a theory would be quite different in it's details than the current ToE, but would likely retain the important details (such as the changes in allele frequency with time) as they remain unchallenged by the finding. This is nothing to be ashamed of: it is the way scientific hypotheses progress and grow in the light of new data.
However, if the findings were not limited to earlier-than-expected rabbits, but included separate data showing that (for example), modern rabbits display unusual features, like a decrease in myxomatosis resistance on generations-long exposure to the disease (which would be a shocking departure from expected findings), then that would mount a more serious challenge to evolution.
In such a case, the initial reaction would probably be an attempt to discern why rabbits, unlike everything else, were not subject to evolution. But, of course, obvious questions would shortly thereafter be asked about whether evolution can then truly be considered universal; and, if not, then how can we be certain that *anything* is really evolving.
In that circumstance, evolution as we know it would probably truly be dead in the water. Of course, reactionaries would likely hold on to their outdated belief in evolution, but eventually the scientific community would have to move on.
Hopefully, a proper, scientific hypothesis/theory would be proposed as an alternative to evolution (and I do not mean ID, as it is not a *scientific* hypothesis) - but it is certainly conceivable that the question would be left open for a while: people have been looking for a Grand Unified Theory in physics for some time now, without noticeable success, so it is possible something similar would happen with evolution.
So, I disagree that evolution is not falsifiable: it certainly is falsifiable.
But any evidence purporting to falsify it must overcome over 150 years of supporting evidence, which is (to say the least) a challenge.
As an example:
The chemi-osmotic theory of respiration was extremely controversial when originally proposed. Previously, everyone had been searching for a chemical intermediate between oxidative phosphorylation and ATP generation.
However, when a scientist (Peter Mitchell, IIRC) conceived it, and then tested it with extremely detailed and convincing experiments, it became apparent that his results were irrefutable.
That did not stop the audience to whom he first presented his results from becoming angry, and refusing to accept them; many venerable biochemists in the audience had spent their entire careers trying to find the chemical intermediate, and he has just demonstrated that their work had been a collossal waste of time.
But, in a short time, it did indeed become accepted by the scientific community as a whole.
This was a pretty radical overhaul of the biochemical paradigm; but it would be nothing in comparison with overturning evolution!
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Edit:
> ".Still can't respond sans the cheapshots, eh? Ah well, I won't judge too harshly your proclivity for old habits."
I'm sorry, but WTF?!
I was actually half agreeing with you there. My point was basically that, since there is SO MUCH supporting evidence for evolution, it would be exceptionally difficult for any new evidence to overturn it. That's all.
> "You described a situation where DE no longer adequately explains the preponderance of evidence. But this is *selection*, not *falsification*."
Perhaps I'm being obtuse here - but I don't see your point.
> "How about: Rabbits decrease in resistance to myxomatosis because natural processes are *blind and unintentional*. It just so happened that there were no advantageous variations."
Ah. Well - if there were no pre-existing resistant members of the population, then it's true there could be no increase (without mutation to introduce the resistance trait). But - if 50% of the original population were resistant, and then 25% of the next generation after myxo. exposure, then 12.5%, then...
So, if the pre-existing resistant members were not selected for in a situation where, according to evolutionary theory, they *should* have been, then that's a problem for evolution.
Of course, alternative explanations for the phenomenon would doubtless be sought and proposed - but it would still be strong evidence against Evolution by Natural Selection.
> "In fact, the disease is such that offspring of infected animals are even less resistant than their parents. It makes no difference"
Granted that this could indeed be one such alternative explanation that a failure of evolution.
But if the molecular mechanisms of the disease were not such that this would be the case, then my original point still stands.
Of course, this would involve more detailed analysis of the disease mechanism - which was my second point (the need for detailed scrutiny of any possible "anti-evolution" findings).
> "DE does not preclude pandemics or extinction. In fact, the extinction of a weaker species and the survival of resistant species is precisely what DE expects: Survival of the Fittest."
Yes, but it does not predict that resistance traits should be selected against in situations where existing theory says they should be selected for.
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Edit (again):
> "1. Sorry, didn't mean to upset you. Cheapshot: ID is not science. That's not the topic. At least qualify it as your opinion."
It is, of course, not just *my* opinion. But for the purposes of this question I'll grant your point.
> "2. In science, we *select* between competing theories. This doesn't mean that the loser has been falsified. The question is whether DE is falsifiable. You are saying it is possible for DE to be on the losing side of a selection process, but that is not the question. I will indicate which of your points addresses *selection* rather than *falsification*."
Again, I'm not certain I see your point.
If a theory is *selected* against because it fails to fit the existing data, and cannot be reasonably re-written to include that data, then it has been falsified.
It is, of course, always possible that subsequent data will demonstrate that the theory was, in fact, always still correct and just mis-interpreted, or the data was misleading, or whatever. But, for the purposes of the current theoretical framework, it is still discarded. It is still falsified.
> "3. Selection. A non-fatal problem that DE would survive."
It's *possible* - but I can't think of an explanation that would get around it and still keep evolution by natural selection as the underlying theory.
Of course - someone else might (I'm not an evolutionary biologist, so cannot claim "expert" status here), but as far as I can see, this evidence would be at the very least extremely challenging for evolution to overcome.
> "4. My point is that you can never say with certainty that there is NOT an explanation that preserves DE. (Before you retort against ID, refer to my earlier comments.)"
Of course not - but remember that proof is impossible in science. The best you can hope for is "proof beyond reasonable doubt (given current evidence".
> "5. Granted, but this would be an anomaly at worst. It would not falsify the theory because you can't prove that an explanation does NOT exist."
Yes - but see my point to 4. above.