Right, but here you have the same code used for a different purpose, while some *other* piece of code is used for the original purpose. If you need endotoxin recognition, why not just use the code that’s already there?
That’s why I asked what you think happened. Why, exactly, do coral, fish, and mammals all have TLR-4* but fish don’t use it for the same thing the other animals do? Do you have an explanation, or are you just trying to nitpick evolution?
(* I’m taking your word for the fact that fish have TLR-4.)
No, Fish don't have endotoxin recognition and signaling. Coral have it with TLR. Humans have it with TLR-4.
Fish have TLR-4, but it does something entirely different.
That's not a gradual, evolutionary, smooth step to smooth step process.
It is, however, what one sees in modern computer programming with code re-use of portions of old programs used in (or slightly modified for) new software.
Not a good idea.
He's correct about that, but only because I informed him of it. Ray-finned fish typically do have TLR-4, although the pufferfish, which has a stripped-down genome, eliminated it.
Coral do not have TLR-4. They have an ancestral TLR protein that does not match any of the fish or mammal TLR subtypes. Since we've been diverging from coral for about half a billion years, that's to be expected.