This is one that that has gotten me more flack than you can imagine. I formulated this idea (not a theory, not a hypothesis, just a notion) way back when I was an undergrad and have seen nothing against it but have only seen evidence for it as a working professor. As a PhD candidate I was advised against talking about it.
I think there exists an underlying principle in biology that is yet unknown but is almost as powerful as natural selection (theory-wise). I think that Sewell Wright was ahead of his time and will someday be regarded as the father of this new synthesis. Wright discussed combinations of genetic traits converging to form nodes on a genetic landscape. These nodes converged around adaptability.
I think there is a principle in biology that causes evolution towards eigenstates like in quantum physics. Combinations of characters that are simpler to arrive at yet may be more complex. Nodes of complexity that are emergent from existing combinations.
I have not yet formed my concept, but think it is valid (at least in part). That is my most controversial opinion!
Wanda: To call you stupid would be an insult to stupid people. I've known sheep who could outwit you. I've worn dresses with higher IQs, but you think you're an intellectual, don't you, ape?
Otto: Apes don't read philosophy.
Wanda: Yes they do, Otto, they just don't understand it.
"A Fish Called Wanda"
™ Version 4.2