Evolution

A system "evolves" if it is subjected to random variations while it is successively stabilized in the variations that improve its functionality. A characteristic paradigm of evolution is the  evolution of a population of reproduced organisms, where random variations of the structure of descendants determine the probability of further reproduction: organisms better adapted to the environment—consequently more "sustainable"—have higher probability to be reproduced, spreading this way their structure in the population. This process, repeated recursively, results in the production of organisms of increasing adaptation and potentially of higher complexity.

 

Bar‑Yam Y., 1997, Dynamics of Complex Systems. Addison Wesley, Reading, Massachusetts, pp. 531-542

http://necsi.org/publications/dcs/index.html

 

See also:

http://en.wikipedia.org/wiki/Evolution