Discrete minds: Stanisław Ulam, automata, and the mathematical recasting of biological pattern recognition.

This article reconstructs Stanisław Ulam's significance for postwar biology and cognition not as the author of a single biological theory but as a contributor to a transformation in representational form. Drawing on Los Alamos reports, Ulam's retrospective framing in Analogies Between Analogies, and the 1974 Mathematical Biosciences article "A Molecular Sequence Metric and Evolutionary Trees," it shows how discrete mathematical models became credible vehicles of biological meaning in the postwar decades. Two examples anchor the argument: cellular automata and recursive growth models, where simple local rules generated growth-like, periodic, and replication-like behavior; and sequence metrics, where molecular relatedness was expressed through the distance between strings. Ulam's work helped normalize two interconnected operations: local rule-based dynamics on lattices and graphs, and metric comparison among structured objects such as pictures and sequences. The article argues that these practices made "information" operational by treating emergence and relatedness as calculable properties of explicit representations. Ulam's influence was frequently indirect and mediated, but historically consequential in widening the range of biological phenomena that could be treated as tractable objects of computation.