Search for Architecture in Complex Worlds: An Evolutionary Perspective on Modularity and the Emergence of Dominant Designs 1 SENDIL K ETHIRAJ University of Michigan Business School 701 Tappan, D5203 University of Michigan, Ann Arbor MI 48109 Ph. 734-764 1230 Fax. 734-936 8716 Email: sendil@umich.edu DANIEL LEVINTHAL The Wharton School of Business 3620 Locust Walk, Suite 2000 University of Pennsylvania, Philadelphia PA 19104 Ph. 215-898 6826 Fax. 215-898 0401 Email: levinthal@wharton.upenn.edu November 2002 1 We thank seminar participants at Stanford University, Northwestern University, New York University, the University of Michigan-Santa Fe Institute Workshop, and The Lake Arrowhead Conference on Computational Modeling in the Social Sciences for useful comments and suggestions.