I know that strictly speaking the term "involution" referring to the evolution theory doesn't hold any meaning. Organisms keep on evolving and changing with time, that's all.
But the following situation could perfectly happen:
Some event causes some organisms to evolve certain characteristics that allow for a better survival, but with time that event stops and what was previously and advantage for these organisms, now it's a disadvantange, and to adapt to the new situation what they do is to exactly remove these characteristics and they end up being exactly the same as they were previously to the change. It could be considered that they have "involutioned".
Are there checked examples of this? (Not just as theory, examples of organisms where this "involution" has been observed). I'm specially interested in "complex" organisms, I think this is not that far fetched to happen to organisms like bacteria, virus or the like. But for more "complex" organisms I guess it's too much of a coincidence.
Edit: I'm putting an example to clarify:
Let's imagine we have a huge amount of plants of the same species which can grow extremely fast (in the way they could simulate 100000 years in evolution in one hour) and we have an atmosphere for them that is the same as current one. (Not realistic, but let's make the thought experiment). We also put some put of these plants apart.
Little by little we go changing all the carbon dioxide in that atmosphere with something, like, for example, nitrogen, it's to expect, that, with time, some plants will appear to better use the nitrogen, at least up to the point where they can survive, as carbon dioxide is every time lower and lower and plants not adapted to this end up dying.
When we finally have only nitrogen processing plants we start the opposite, we start filling little by little with carbon dioxide, it's to expect that the contrary would happen.
Now, if a biologist were to observe the plants that were set apart at the beginning and the new created plants he wouldn't be able to tell where each plant is from, unless he was aware they were separated to do the experiment.