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Spontaneous evolution of modularity and network motifs

Summary: Spontaneous evolution of modularity
and network motifs
Nadav Kashtan and Uri Alon*
Departments of Molecular Cell Biology and Physics of Complex Systems, The Weizmann Institute of Science, Rehovot 76100, Israel
Edited by Curtis G. Callan, Jr., Princeton University, Princeton, NJ, and approved August 2, 2005 (received for review May 10, 2005)
Biological networks have an inherent simplicity: they are modular
with a design that can be separated into units that perform almost
independently. Furthermore, they show reuse of recurring pat-
terns termed network motifs. Little is known about the evolution-
ary origin of these properties. Current models of biological evo-
lution typically produce networks that are highly nonmodular and
lack understandable motifs. Here, we suggest a possible explana-
tion for the origin of modularity and network motifs in biology. We
use standard evolutionary algorithms to evolve networks. A key
feature in this study is evolution under an environment (evolu-
tionary goal) that changes in a modular fashion. That is, we
repeatedly switch between several goals, each made of a different
combination of subgoals. We find that such ``modularly varying
goals'' lead to the spontaneous evolution of modular network
structure and network motifs. The resulting networks rapidly


Source: Alon, Uri - Departments of Molecular Cell Biology & Physics of Complex Systems, Weizmann Institute of Science


Collections: Biology and Medicine