The author wants to thank the following individuals for stimulating discussions on the topic of the paper: Lee Altenberg, Leo Buss, Jim Cheverud, Junhyong Kim, Manfred Laubichler, Bernhard Misof, Christian Pazmandi, Andreas Wagner. The financial support by the Yale Institute for Biospheric Studies and NSF grant BIR-9400642 is gratefully acknowledged. This is contribution CCE-#25 of the Yale Center for Computational Ecology.