I am going to talk about any scientific theory in general, it could be in the field of biology, physics, chemistry, Earth science or astronomy.
First off. All scientific theories - including Evolution - can be challenged, questioned and replaced by any alternative theories.
But any such alternative must have not only better explanation than the current scientific theory, it must also have enough evidence to back up the alternative.
Second.
I am sorry if I am repeating myself, but you need to use correct terminology in sciences.
Sciences relied on tests or testings, observations, evidences, experiments.
And the test will either "verify" or "refute" the model/hypothesis/theory.
That's how sciences determine which model or hypothesis or theory is "scientific".
Sciences don't rely on proofs.
Proofs are logical statements or logical models, and the most common forms of proof used in sciences and mathematics are mathematical equations.
So when you use words, like "prove" or "disprove", it would mean you are attempting to solve equations.
Proofs or mathematics equations are not evidence.
Evidence are physical where proofs are logical abstractions.
Evidence are used to determine if the hypothesis or theory is scientifically true; proofs don't do that.
Plus, the explanations and predictions are actually models in the hypothesis or theory, and so are proofs (proofs are logical models), so when you are testing hypothesis or theory, you are also testing the explanations, predictions AND any mathematical equations (or proofs).
Proofs are not true, until they have been tested as true with observed physical evidence.
So the proper terminology is to "verify" or to "refute" or "debunk" Evolution, not to "prove Evolution" or "disprove Evolution".
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As to the theory of Evolution..going back to your original questions.
There may be better alternative theory in the future that may replace Evolution, but I really don't think so.
I think it is more likely biologists will -
- either expand the current theory
- or correct & update the current theory of Evolution
Because the theory is already correct as they are, and there are enough evidence to support all the current mechanisms of Evolution.
If you didn't know already, the mechanisms of Evolution are:
- Natural Selection
- Mutation
- Genetic Drift
- Gene Flow
- Genetic Hitchhiking
Natural Selection haven't been replaced by other mechanisms, so instead of replacing Natural Selection, they add the new mechanisms to the old theory of Evolution.
What people - non-biologists - don't understand that since Darwin published On Origin of Species (1859), new evidence provide new information, and these evidence/information will either be added to the "Theory of Evolution" or it will correct/amend and update what they already know.
And Evolution have expanded many times over the decades and century after On Origin, including genetics (Mendelian inheritance), mutations, genetic drift, DNA testings, etc.
I highly doubt that they will ever replace Evolution. They will more likely add new information to the current theory, expanding or updating Evolution.
And btw, Xavier Graham.
Understanding Evolution is fundamental part of biology, that explain the biodiversity of species. So what it is learned or taught shouldn't affect religions, because no religions teach biology.
Only ignorant creationists who are weak and insecure in their faith, have trouble with Evolution.
PS
The "survival of the fittest" isn't a name for an evolutionary mechanism; the correct name is Natural Selection.
Personally I think biologists shouldn't use "survival of the fittest", because non-biologist people tends to misunderstand what this term mean.
Some people think Natural Selection is about being the strongest, smartest or fastest, when they misuse "survival of the fittest". It isn't. It simply mean being adapted to the changed environment.
Do you think koalas, wombats or butterflies are here today, because they are strongest, fastest or smartest?
People are absolute idiots when they think strength, speed or intelligence lead to survival of the species; this is why I think biologists should drop "survival of the fittest" when teaching biology to student.