So if we compare all the small subunit rRNA sequences - several hundred by now - we can't learn anything from them?
Yes. That was my point. We can learn -- and did in fact -- learn a lot by comparison even if there were no evolutionary theory.
It told a great deal about structure and function. Sequence analysis is very simple, yet very powerful. It provides a great deal of info and insight on structure and function.
A ribosome's a ribosome. The main information 16S gives you is evolutionary relationships
bttt