The beginning of Life on Earth Biochemistry

Let us ignore for the remainder of this book the idea that we were visited by aliens, and return to a more scientific discussion of how chiral life began. We have seen in this chapter various theories as to how the primordial ponds could have been seeded with L-amino acids or their precursors. The two main ideas discussed so far are that chiral organic molecules rained down on the earth billions of years ago, or alternatively there is a natural energy difference between spatial enantiomers, resulting in a natural difference in the concentration of the different enantiomers that may have been present. In each of these cases, one predicts a mixture that is not racemic, but provides the chemical events to the beginning of life with an enriched chiral pool of starting material. 

A natural question is how much of an excess do we need in the chiral pool. Do we need the 10% or so that the optimistic predictions of chiral photodestruction in space might give us, or will the one molecule in 10 predicted by the parity-violating weak interaction be sufficient In thinking about this question we need to keep in mind again that we have billions of pools over billions of years, so that even if the chemical reaction that we need to get life started is very rare, we have lots of time and many pots to work with. In most of the attempts to answer 

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