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I have never seen a plausible scenario to explain why all organic matter (or almost all) is L and not D.

There are two non-conflicting ideas of which I am aware personally concerning why biological proteins are L and sugars are D. The main one is that the first replicator happened to be made of L stuff, so the L-handedness basically won the race to self-replication. The L-replicators then formatted the pre-biotic soup to L-handedness by the simple act of copying themselves.

Another point is that L- and D- isomers have slightly different energies because of the handedness of the weak force. The "biological" form of a molecule tends to correspond to the lower of the two energies.

Thank you for the reply.

First, about energies. Are you completely sure that L is less energy? Because chirality is not like normal isomers in that it is just different in configuration, and not bond repulsion (why cis is more energetic than trans in certain bonds).

If this were the case (that L is less energetic) it would not only refute your first explaination (that it simply won the race), but it then need to be correct for sugars as well.

Now onto your first explanation. The problem here is this: there is no reason why there weren't equal or mostly equal concentrations of both, most likely in a heterogeneous mixutre. Therefore, there is no reason why the region where magically self-replicating matter occurred wouldn't have sparked BOTH L and D at the same time, thus making them equally competitive and likely. Given the relative infinite of energy (to those little molecules), any energy disparity between L and D would be irrelevant and not a selective factor.

This is why the problem is such a conundrum--there is no reason why L won over D. There were unlimited resources relative to the "organisms" or pre-organisms. There was unlimited space to expand (else neither would have flourished). It is as if something arbitrarily picked one of the two.

However, the magical "starlight" transformation in space that I talked about does account for the disparity--hence why it is mainstream, in the very least.

I don't believe, as you apparently do, that evidence supports automatic qualities on nature (IE the "race to self-replication" implies it was a forgone conclusion that "something" would do it).