@Khandro
Hypo;//Always bear in mind that what we see today is the competition winner//
You're steering away towards a discussion on evolution which isn't relevant and is universally accepted - by all but the seriously weird. //
You appear determined to not accept that there primitive, barely competent precursors to DNA.
A precursor organism, lacking the repair mechanism would suffer a high mutation rate so as soon as a self-repairing mutant comes about, the latter will prevail, simply by having fewer progeny lost to mutation damage. It will have a harder time adapting to environmental change because its genes are more stable but survival is a lottery anyway.
I stand by evolution as a theory and one logical upshot of that is that, just like winding back the universe to the big bang, we must wind back life processes to more primitive, less elegant, less efficient forms. I'm sure you'd like to wave it away but I see it as unavoidable because you wanted to discuss ancient DNA.
//I refer to the recent //
see my previous post ^^^^
//findings of DNA, which we now see contains the ability to self-repair and must have been able to do so millions of years ago - why is this,//
Every time DNA strands are copied, incorrect partner purine/pyrimidine letters get plopped into place by the copying enzyme. (Molecules bumping into one another: it gets a bit random, at times. Heh heh). The repair proteins drift along the strand performing a 'verification' process. Snipping subunits out and slotting correct units in is a multi-step process and consumes energy (ATP molecules) in breaking/remaking bonds.
// and does this extraordinary quality come about by accident? //
A long sequence of accidents, to be more precise. If an accidental change in a gene causes an advantageous change in the protein it codes for then it is going to be preserved.
// And as a sub-question; aren't you absolutely staggered in wonder? //
I'd be surprised any species could maintain its shape for a lifetime, let alone down the generations, if DNA didn't have a self-repair system, to be honest.