FITNESS OPTIMIZATION AND DECAY OF EXTINCTION RATE THROUGH BIOLOGICAL EVOLUTION

We present a simple theoretical model of evolution featuring a decreas ing extinction rate due to an increasing average fitness of the specie s. The dynamics is based on a random walk on a rugged fitness landscap e, with evolutionary jumps for each species triggered by the achieveme nt of fitness records during the walk. We analyze two different rules for extinction. In the first, an evolutionary jump leads to an extinct ion with a given probability, while in the second a specific competiti on mechanism is considered. In both cases temporal power laws are foun d to describe the evolution. Extensive simulation results from our sec ond model are in reasonable agreement with paleontological data, showi ng that the background extinction rate has decreased since Cambrian ti me.