I think I understand what your saying...and thank you for taking the time.
In my opinion, you might be confusing what a human is with what a human does, or is capable of doing.
To keep it simple, a human is what is birthed from combining a male human sperm with a female human egg. Now we can choose to travel into space, or maybe even one day live on another planet. If we did, we may evolve to that environment, much like astronauts start to evolve when they spend to much time in space. Their bones get brittle, but their senses learn how to become oriented in a zero gravity environment. That doesn't change who they are or make then less human, it just means they've adapted to their environment. Humans have always been able to adapt.
To use an example on earth, when a blind person develops an incredible sense of hearing and smell to compensate for their lack of vision. That doesn't make them any less human, they've just adapted or evolved. So I think we can define what a human being is, while still allowing for changes. After all, no 2 human is exactly the same, but we are all part of the same species. Even if we start to incorporated computers to our body...which we already do with pacemakers and other medical devises, we still remain human. We're just attaching something to our body.
My only point in all this was to say we need to always make sure a human has the last word. I don't ever want to live in a society where computers judge us. We can, and do, use computers as tools to help us make decisions, but that's very different than a computer having the last word. Hope I've explained my self properly.