Indeed...you raise an excellent point. There is really no rule other than a numbers game to determine what is the “normal” gene and what is the “mutation.” If a population is all blue-eyed (and just for this example let’s just assume for a moment that eye color is based on one set of genes) and a change in the blue eye gene occurs and an individual is born with brown eyes, then that is the “mutation,” whereas in other populations the brown eye is normal and the blue would be the mutution.
First of all, the word "evo" is a term of derision which translates roughly as: "since I hate science and can't argue with facts and reason, I'll just call you nasty names."
Second, to answer your question: over the long period of four billion years, all DNA codings were once mutations from whatever came before.
Useful mutations survived, multiplied and so became standard in following generations.
But the rate of DNA mutations is quite small -- maybe one per generation -- and most are not helpful.
Finally, computer comparisons of different DNAs from around the world can show which mutation-changes are relatively recent and which more ancient.