Simple(?) Life-form to Human evolution cannot be demonstrated nor tested... evo-fundies will not even attempt to begin to explain it from the beginning over in the ''enlighten'' me thread... care to give it a go?
FoeHammer.
Actually, this sort of question betrays a misunderstanding of what the theory of evolution is about.
The theory of evolution is not about the history of evolution. The theory does not, in principle, predict the history.
The theory of evolution is about the process of evolution--about how evolution happens.
I take it you actually have no difficulties with the process of evolution. You understand about mutations and variation and natural selection and speciation. Right? And you agree this has all been observed, so we know that evolution happens and how it happens.
Now what is the relation of the process to the history of evolution?
1. The process of evolution presumes a history of evolution. From the existence of the process we can infer that today's species are descendants of earlier species and that they can be grouped via their relationship to common ancestors among those earlier species.
What that does not tell us, however, is which species are closely related to each other via a recent common ancestor. That is information we have to reconstruct from morphological, paleontological and genetic evidence.
Note, however, that the theory of evolution is not affected by whatever particular history we reconstruct. If the evidence showed that humans were more closely related to seals than to chimpanzees, that would still be consistent with the theory of evolution. (It would imply that we have a different bodily configuration than we do, but it would still be a theoretical possibility.)
2. What applies to recent evolutionary history also applies to more remote evolutionary history. Just as in genealogy. Once we have grouped siblings according to their common parent, we can then group these groups by common grandparent, then group the larger groups by common great-grandparent, as far back as a universal common parent (e.g. mitochondrial Eve or chromosome Y Adam).
So with species.
Now what the theory tells us is that whatever historical reconstruction we end up with, it will take the same form as a family tree---namely a nested hierarchy. The theory does not, in itself, tell us where the phylogenic tree is rooted. (It doesn't even tell us if there is only one tree or several). And it doesn't tell us in what directions it will branch or which species past or present will be on which branches. That is information we have to reconstruct from the data. But, what the data tells us about the history does not affect the theory---unless and until we have data that sits outside the nested hierarchy.
Any history of species' ancestry that respects the form of nested hierarchy would support the theory of evolution.
So we do not have to confirm the particular history we have reconstructed in order to validate the theory of evolution.
The standard phylogeny supports the theory of evolution because it is a nested hierarchy, and because the same nested hierarchy is confirmed by multiple lines of evidence. But any biological nested hierarchy would do the same.
3. Once we have a relatively certain partial reconstruction of the history of evolution, we can use the theory to predict how the unknown portions of the history can be filled in. This is akin to knowing that if a train went from Montreal to Toronto, it must have passed through Kingston on the way.
So, once it was fairly clear that whales evolved from terrestrial mammals, we could imaginatively envision what sort of species would exist during the transition from land to water and predict that somewhere in the fossil record we would be likely to find such species. And lo and behold! we have found such species.
One can even get more detailed. One of the key changes that would have to occur in whale evolution is changes in the ear to go from the poor hearing terrestrial animals have in water to the excellent underwater hearing of whales. Study of intermediate fossils show exactly the sort of changes in the ear predicted by the theory.
Even more spectacular was the successful prediction of an early species in the fish->tetrapod lineage which led to the discovery of
Tiktaalik roseae.
In addition to being able to predict from partial evidence what we will find at various points in the fossil record, researchers studying how viruses mutate are now beginning to predict successfully how the flu virus will mutate in the future so that we can be prepared for next year's flu bug with the appropriate medication.
So to get back to your question. It is not really a question about whether evolution happened in the past. The multiple lines of evidence supporting the standard phylogeny do that already. What you are really asking is whether we have reconstructed the phylogeny correctly. But that is neither here nor there with validating the theory of evolution.
Have we reconstructed the phylogeny correctly? In part, yes. And parts are still unknown and parts will need correcting as we get new data. What is important is that all of the known data supports the standard phylogeny.
Furthermore, the only theory that predicts a phylogeny such as the standard phylogeny is the theory of evolution. I say "such as the standard phylogeny" rather than "the standard phylogeny" because the theory does not predict the particular history of evolution on earth. It predicts a history.
If we ever find another planet with evolving biological life on it, we can predict from the theory of evolution that it too will have a history in the form of a nested hierarchy. But we will have no idea what that history was until we start reconstructing it.
So the kind of question you are asking, while valid in determining exactly what the history of evolution was on earth, really does not impinge on the theory of evolution at all.