It's never been observed anymore than creation has. All of PH's links won't show that ANYONE has observed evolution happening. If that was true, it would be world wide. I don't get into debates on cre/evo threads because I already know what I believe and don't care about changing your mind.
So if a human didn't observe it, then evidence of something isn't enough?
Well that would prevent you from believing a lot of things. Like whether OJ did it.
I was present when my father and some co-workers observed bacterial speciation in a laboratory. That is, they observed bacteria split into two groups that did not interbreed through exchange of genetic material. It was old hat then (in the 1950s.)