A classification of replicators and lambda-calculus models of biological organization.

W. Fontana & 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 certain minimal chemistry. Although this idea is very promising, their concrete formulation could be improved if suggestions for the following items were incorporated: (i) a better coding of chemical reactions; (ii) a reinterpretation of the evolutionary behaviour of autocatalytic chemical networks; (iii) a better appreciation of morphological and genetic factors; (iv) a more complete embedding of the theory into the background 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 hereditary replicators). Suggestions to facilitate improvement are made explicit in this paper. The most challenging task would be to model the transition from processive, limited hereditary replicators to modular replicators with limited and unlimited heredity.