[nlitened]

As I understand, earlier forms of life used RNAs as building blocks (instead of proteins encoded in DNA->RNA), so protein-based life _was_ a completely different form of life.

Some of the oldest replication machinery in our cells still uses the good old rusty RNA building blocks at its core (however nowadays they're propped up with proteins), and the newer machinery is almost entirely "high tech" proteins.

So you could say that in the billions of years, entirely new life forms were created, and they just completely displaced the older, less effecient ones. Probably pure-RNA life forms were not even the first ones, and they completely displaced even more primitive prior biotechnology when they appeared.

[tardedmeme]

This is, at this point in time, still a hypothesis.