L-Leucine, L-aspartate, and D-glucose bind in a stereospecific manner to a colloidal clay, bentonite. This binding has high-affinity, saturable characteristics. The biologically uncommon enantiomers, D-leucine, D-asparatate, and L-glucose, do not exhibit any selective absorption on bentonite. It is suggested that this difference between stereoisomers could account for the evolution of life forms possessing a great preponderance of L amino acids and D-glucose.