of course, this ancestral gene may no longer exist, but if it marijuana-the-pros-and-cons-of-legalization is ever discovered, that would fill in a major hole. so here is a prediction of the model: a non-rearranging receptor with an immunoglobulin domain existed in the ancestor to the jawed vertebrates. however, no direct marijuana-the-pros-and-cons-of-legalization homologue to the antibody proteins have been found. because its structure is so stable, a large portion of cell-surface molecules possess it, even some related to immunity (outside of the jawed vertebrates).
there seems to be ample evidence suggesting that the RAG genes were once transposases, do you dispute this? the fact that they have transposase activity (in vitro) basically says it all. and the evidence marijuana-the-pros-and-cons-of-legalization supporting it:. those changes were beneficial to the host. would be under the marijuana-the-pros-and-cons-of-legalization receptor's transcriptional control.