Self-organized Criticality in Living Systems
  We suggest that ensembles of self-replicating entities such as biological systems naturally evolve into a self-organized critical state in which fluctuations, as well as waiting-times between phase transitions are distributed according to a 1/f power law. We demonstrate these concepts by analyzing a population of self-replicating strings (segments of computer-code) subject to mutation and survival of the fittest. 
C. Adami (Kellogg Radiation Laboratory, Caltech)