Most biomolecules are "chiral", that is to say they exist in two left and right -handed mirror image forms. But biology only uses one hand, i.e. it is "homochiral". Life on Earth is made of left handed amino acids, almost exlusively. One of the greatest puzzles in biophysics is the question of why life on Earth is based on left-handed (L) amino acids?
Recently Prof. Pedro Chintas (Angew. Chem. Int. Ed. 2008. 47. 2-5.) described that fractional sublimation of enantiomeric excess(ee) compounds may improve substantially a small ee. (This results a useful protocol for resolving racemate, and suggest that the improvement of optical activity attained by such thermal process could be more efficient than or at least an alternative to, spontaneous crystallization of suitable compounds)
He conclude that sublimation should be regarded as a reasonable mechanism for the formation of optically active crystals. These optically enriched crystals of enantiopure compounds easily conducted by natural agents might have generated highly enantiopure niches in the prebiotic world.
Molecular evolution might lead to life but it is not scientifically valid because life is a non- physical, non-chemical entity.