Yeah, replicating the entire brain is a herculean effort. However, it’s also important to keep in mind that the brain evolved for robustness, and has a lot of redundancy in it. It turns out that we’d only need to implement a neural network that’s roughly 10% of the brain to get a human level intelligence as this case illustrates. That seems like a much more tractable problem. It might be even smaller in practice, since a lot of the brain is devoted to body regulation and we’d only care about the parts responsible for thought and reasoning.

I think the biggest roadblock is in figuring out the algorithm behind our conscious process. If we can identify that from the brain structure, then we could attempt to implement it on a different substrate. On Intelligence is a good book discussing this idea.