A CLASSIFICATION OF REPLICATORS AND LAMBDA-CALCULUS MODELS OF BIOLOGICAL ORGANIZATION

W. Fontana and L. W. Buss (Proc. Natn. Acad. Sci. U.S.A. 91, 757 (1994 ) and Bull. math. Biol. 56, 1 (1994)) have put forward a scheme for a theory of biological organization based on the lambda-calculus. Their key innovation was to represent, with the aid of this calculus, a cert ain minimal chemistry. Although this idea is very promising, their con crete formulation could be improved if suggestions for the following i tems were incorporated: (i) a better coding of chemical reactions; (ii ) a reinterpretation of the evolutionary behaviour of autocatalytic ch emical networks; (iii) a better appreciation of morphological and gene tic factors; (iv) a more complete embedding of the theory into the bac kground of relevant earlier contributions. Confusion can be stopped by the application of a proper classification of replicators (important categories being: processive and modular, limited and unlimited heredi tary replicators). Suggestions to facilitate improvement are made expl icit in this paper. The most challenging task would be to model the tr ansition from processive, limited hereditary replicators to modular re plicators with limited and unlimited heredity.