Slight sidetrack: By the time AI seems plausible, I think it's likely that the human race will have done enough self-modification (computer augmentation, biological engineering) that the question of what's human is going to be more difficult than it is now.
By 'human', do you mean 'member of the species Homo sapiens' or something else?
If it's worth saying, but not worth its own post, even in Discussion, it goes here.