50 years ago, the immune system was little cells valiantly defending our bodies against invaders and fusion was using magnetic fields to try and slam deuterium and tritium atoms together. We have since learned a huge amount about how the immune system works, and have understood what a truly neat job much of life is, and how much we still have to learn; while fusion is still using magnetic fields to try and slam deuterium and tritium atoms together.
We may have grey goo in our lifetimes. Right at the end of all of our lifetimes if we don’t do it right.
Making spare parts and swapping bits seems to be something that life has never really tried. Things like hermit crabs swap their shells, but that’s not quite the same thing. It may be that robots have options that living things don’t.
