Symbiosis in the Bak-Sneppen model for biological evolution with economic applications

In the present work we extend the Bak-Sneppen model for biological evolution by introducing local interactions between species. This "environmental" perturbation modifies the intrinsic fitness of each element of the ecology, leading to higher survival probability, even for the less fit. While the system still self-organizes toward a critical state, the distribution of fitness broadens, losing the classical step-function shape. A possible application in economics is discussed, where firms are represented as evolving species linked by mutual interests. (c) 2005 Elsevier B.V. All rights reserved.