Yes, that was my thought also. Indeed, I am much more skeptical about postulating chirality of radiation than of chemical compounds, so the problem seems to have been made bigger.
When you boil it down, there are only three natural explanations of a perceived asymmetry: an intrinsic asymmetry in physical law - and that dog fer sure won't hunt - an existing prior asymmetry, and a spontaneous symmetry breaking.
Well, the Earth does have two known asymmetries - its direction of rotation and the polarity of its magnetic field. The former raises an immediate problem - best illustrated by the old "water down the toilet" joke - any asymmetry in the northern hemisphere would surely require the opposite asymmetry in the southern. So maybe, just maybe, the chirality happened at a time when one hemisphere was ocean and the other land, so only the left-handed guys made it. That hypothesis is testable once we have enough evidence about past continental drift.
But the combination of rotation and magnetic polarity creates a true asymmetry. The problem there is that we have no mechanism for how the earth's magnetic field could affect chemical composition.
So for now, I fall back on spontaneous symmetry breaking. Start with a world half full of primitive L critters, and half full of their R mirror images. As we know, L must eat L, and R must eat R. But you can't tell them apart - not if you're a primitive cell.
Now a random event - maybe a tsunami - tips the balance to 51% L and 49% R. The L's are now slightly more successful at eating, because 51% of what they find is useful food. This advantage magnifies over time, until all the Rs have starved.
Again, verifiable in principle if we could find some primitive microfossil with the opposite handedness. Way, way back in time, so not much chance; but not zero chance.
A great puzzle. In fact, it is #2 on the list of puzzles I worry about late at night. (Should you care, #1 is the apparant time asymmetry in the decay modes of the neutral kaon)
Unfortunately, that's an Urban Legend.. it's the same direction for north and south of the hemisphere..
As for the magnetic field, I'm just not sure what you're talking about..
Deformity caused by Solar Wind?
Not starved, been eaten.
Good analysis though.
Humble, thought that you might want to weigh in here.
I am 90% sure I remember that bacteria use both right and left-handed A.A.s.
It is evolutionarily consistent that eukaryotes only use left, and that's an interesting article proposing a reason.
"So for now, I fall back on spontaneous symmetry breaking. Start with a world half full of primitive L critters, and half full of their R mirror images. As we know, L must eat L, and R must eat R. But you can't tell them apart - not if you're a primitive cell.
Now a random event - maybe a tsunami - tips the balance to 51% L and 49% R. The L's are now slightly more successful at eating, because 51% of what they find is useful food. This advantage magnifies over time, until all the Rs have starved. "
I'd like to laugh at this, but I think you might actually be serious. I have a bug in a flask right next to me. They are, of course "L" in amino acids. They will eat almost anything and they don't give a crap if it's D or L.
No, life had to start as all D or all L. The question is why L was favored and if there is something inherent in L that makes it better. It has been suggested a number of times, but I don't think the evidence is unambiguous at this time. Besides many sugars are D form.
Now you're scaring me. :^)
Zero chance is about right, since an optically active amino acid racemizes over a period of time to eventually become a 50-50 mixture of the D and L isomers. The time frame is different for each amino acid, and has been (attempted) to be used as a biological clock. However the process is sensitive to temperature and moisture, so it isn't a true "half-life" phenomenon. The time frame as I recall is on the order of a few thousands, to maybe a few hundreds of thousands of years, and would be long done after the millions or billions of years you are wanting to look at.