[lone-commenter]

I meant that it's dubious whether we can reproduce a brain-like machine until we'll understand the matter well enough to either prove it possible or impossible.

Anyway, I feel like you. If it's been done once, it can't be impossible in any meaningful sense.

Further, the argument from lack of understanding would work only if knowledge (and science) could not advance any further; but that's tough to prove -- not to say that it's used over and over in faith vs. reason debates to the point it's become annoying -- so the argument is quite weak.