EXTINCTION - BAD GENES OR WEAK CHAOS

The dynamics of extinction and diversification of life is not a simple random process, driven by arbitrary inputs. Biotic interactions are k nown to play a very important role in the population response to physi cal factors. In spite of this fact, it is not clear how the ecological scale is related with the macroevolutionary one. In this paper we sug gest that both levels are, at least to some extent, decoupled. Using a simple model of large-scale evolution, we show how an n-species ecosy stem evolves towards a critical state where extinctions of all sizes a re generated. This state involves a situation where high unpredictabil ity is present. The basic properties of the overall macroevolutionary pattern are well reproduced and a new interpretation for this process is suggested.