Evolution through natural selection has been going on for a very long time. Evolution through artificial selection has been practiced by humans for a large part of our history, in the breeding of plants and livestock. Artificial evolution, where we evolve an artifact through artificial selection, has been around since electronic computers became common: about 30 years. Right from the beginning, people have suggested using artificial evolution to design electronics automatically.l Only recently, though, have suitable re­ configurable silicon chips become available that make it easy for artificial evolution to work with a real, physical, electronic medium: before them, ex­ periments had to be done entirely in software simulations. Early research concentrated on the potential applications opened-up by the raw speed ad­ vantage of dedicated digital hardware over software simulation on a general­ purpose computer. This book is an attempt to show that there is more to it than that. In fact, a radically new viewpoint is possible, with fascinating consequences. This book was written as a doctoral thesis, submitted in September 1996. As such, it was a rather daring exercise in ruthless brevity. Believing that the contribution I had to make was essentially a simple one, I resisted being drawn into peripheral discussions. In the places where I deliberately drop a subject, this implies neither that it's not interesting, nor that it's not relevant: just that it's not a crucial part of the tale I want to tell here.

1. Introduction.- 1.1 Topic.- 1.2 Hardware Evolution.- 1.3 Motivation.- 1.4 The Thesis.- 2. Context.- 2.1 Inspiration.- 2.2 Evolutionary Algorithms for Electronic Design: Other approaches.- 2.3 Multi-Criteria EAs: Area, Power, Speed and Testability.- 2.4 A Philosophy of Artificial Evolutionx.- 2.5 The Position of this Book Within the Field.- 3. Unconstrained Structure and Dynamics.- 3.1 The Relationship Between Intrinsic Hardware Evolution and Conventional Design Techniques.- 3.2 Unconstrained Structure.- 3.3 Unconstrained Dynamics.- 3.4 The Relationship Between Intrinsic Hardware Evolution and Natural Evolution.- 4. Parsimony and Fault Tolerance.- 4.1 Insensitivity to Genetic Mutations.- 4.2 Engineering Consequences of Mutation-Insensitivity.- 4.3 Explicitly Specifying Fault-Tolerance Requirements.- 4.4 Adaptation to Faults.- 4.5 Fault Tolerance Through Redundancy.- 4.6 Summary.- 5. Demonstration.- 5.1 The Experiment.- 5.2 Results.- 5.3 Analysis.- 5.4 Interpretation.- 6. Future Work.- 6.1 Engineering Tolerances.- 6.2 Applications.- 7. Conclusion.- Appendix A. Circuit Diagram of the DSM Evolvable Hardware Robot Controller.- Appendix B. Details of the Simulations used in the 'Mr Chips' Robot Experiment.- B.1 The Motor Model.- B.2 The Movement Model.- B.3 The Sonar Model.- References.