Well, you assume that there is no other explanation than your's that is based on the evidence.
It's not an assumption, it's an observation. I observe that there are no alternatives to evolution that are based on the evidence. All the alternatives are based on ignorance.
Many who believe in ID or Creationism would ironically also think that their explanation is derived straight from the evidence (granted many also blindly believe it, which I don't endorse).
But I observe that they are wrong - that they have based their arguments on evidence which does not actually exist.
what's the point in studying science or debating if your conclusion is already made up?
My mind is made up, but it's also open to new evidence. I've come to a conclusion based on the evidence that we have. At such time that we have additional evidence, I'll see if I need to change my mind. But until then, there's no reason to.
Lastly, if you truly hold to Solipsism, then there really is absolutely no point in studying science or debating at all, bacause you can never know anything whatsoever (outside of your existence).
My VCR works no matter if its a really real object, or just a figment of my imagination. Science leads to testable predictions about our experiences no matter if those experiences reflect real reality, or if they're part of a shared hallucination. Science is the only method of constructing models in the face of solipcism. And the thing about solipcism is, you can't rebut it.
Because in Solipsism, all you can truly know is your own existence.
I can't even know that. But in the meantime, thanks to science, I can surf the internet.