My issue is that from a scientific point of view, physicalism is all we have. Everything else is belief, or some form of faith.
Your example about relativity is good. It might have sounded insane at some point, but it turns out, it is physics, which nicely falls into the physicalism concept.
If there is a falsifiable scientific theory that there is something other than a physical mechanism behind consciousness and intelligence, I haven't seen it.
I don't think science and consciousness go together quite well at this point. I'll claim consciousness doesn't exist. Try to prove me wrong. Of course I know I'm wrong because I am conscious, but that's literally impossible to prove, and it may very well be that way forever. You have no way of knowing I'm conscious - you could very well be the only conscious entity in existence. This is not the case because I can strongly assure you I'm conscious as well, but a philosophical zombie would say the same thing, so that assurance means nothing.
There are more than one theories, as well as some evidence that consciousness may not exist in the way we'd like to think.
It may be a trick our mind plays on us. The Global Workspace Theory addresses this, and some of the predictions this theory made have been supported by multiple experiments. If GWT is correct, it's very plausible, likely even, that an artificial intelligence could have the same type of consciousness.