I don't have an example (not my field), but if an environment for a species
changes rapidly, it will take time for it to reach genetic equilibrium as it adapts.
Until then, one could say it's not as highly evolved as it could be.
If I understand you correctly, under your scenario an organism is considered to be highly evolved if it's well adapted to its environment, say environment A. If environment A should change to environment B, which is hostile to the organism, the organism loses it's "highly evolved" status. But if environment B should change back to environment A, the organism would regain its status as highly evolved. So the organism went from highly evolved to not as highly evolved to highly evolved, and all without changing one wit.
The way I see it, one can say any organism that has gone through a tremendous (high) amount evolution is highly evolved. It evolved an awful lot rather than a little.
Thing is, all organisms have gone through a tremendous amount of evolution, even simple life forms. It all depends on where one sets the starting line. That it's environment suddenly changes leaving the organism less than best adapted doesn't take away the fact that it is highly evolved: It went through a tremendous amount evolution.
Because of the above reasons the concept of "highly evolved" is next to meaningless, not entirely so, but next to.
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