Adaptive evolution.
Adaptive evolution is just another way of saying natural selection, without ever describing anything physical. It's circular reasoning at best.
With all the overwhelming evidence that the theory of evolution supposedly has at it's disposal, you offer this as evidence that natural selection is a valid mechanism in a scientific theory, per your own terms.
No offense, but that's simply pathetic if you ask me.
Don't feel bad though, no one, in the years that I've been asking this question, has ever been able to answer it, and the reason is because evolution is not a valid scientific theory. If it was, then the question would easy to answer and demonstrate. It's that simple...or should I say, it's that fundamental.