What would change your opinion that we descended from something other than humans?
Oh, lots of things. For example, if you could find modern human skulls in layers that date prior to the ape-man skulls, that would cast serious doubt on whether we evolved from these humanoid creatures, (which really did exist and which really do change through the fossil record in a seamless fashion from remarkably chimp-like creatures to remarkably man-like creatures).
Alternatively, someone could find a fossil that does NOT fit into this chain, or into any logically compatible branch of it. For example, suppose somebody found a humanoid creature with a large, human-like brain and an ape-like jaw. Such a thing would not fit in with the rest of the fossil evidence at all. That's how the Piltdown forgery was detected. But if such a fossil were found and verified, it would cast serious doubt on human evolution.
Another possibility would be that our DNA is not structured in a way that is compatible with gradual transitions from ape to man. For example, let's suppose that the genetic evidence showed that chimp DNA was just monkey DNA with a whole bunch of little changes. I can also say something about the DNA of ancient apes ancestral to us, by focusing on sets of changes that are common to gorillas and chimps. (This works because chimps and humans share a common ancestor more recent than chimps and gorillas, thus any chimp-gorilla common ancestor must, if evolution is correct, be ancestral to us.) Suppose further that human DNA was just ancient-ape DNA with more changes, except for a significantly large section that doesn't have the monkey-to-ancient-ape changes. It would be as if some chunk of the DNA went from monkey to man without passing through our putative ape ancestor. That would falsify human evolution.
Now, what would you say about human evolution, if those skulls and their dates were proven correct?