[AndrewC]

Protamines that, in the AndrewC fictional version, should be identical to any pruative protamine that may have served that function a billion years ago.

It doesn't matter how long ago, a minor change is a minor change. We know that the histone that we are considering is practically "eternal". A minor change constrains the changee if the change-target is "fixed". Any more futile attempts to distance yourself from your fiction? homologs such as the protamines may well have served some entirely different function before doing what histones do now. A minor change to that homolog, and presto - histones .

[Senator Bedfellow]

We know that the histone that we are considering is practically "eternal".

But we don't know that about protamines, do we? How many ways do you want me to say the same thing before you get it?