All living things are remarkably complex, yet their DNA is unstable, undergoing countless random mutations over generations. Despite this instability, most animals do not grow two heads or die, plants continue to thrive, and bacteria continue to divide. Robustness and Evolvability in Living Systems tackles this perplexing paradox. The book explores why genetic changes do not cause organisms to fail catastrophically and how evolution shapes organisms' robustness. Andreas Wagner looks at this problem from the ground up, starting with the alphabet of DNA, the genetic code, RNA, and protein molecules, moving on to genetic networks and embryonic development, and working his way up to whole organisms. He then develops an evolutionary explanation for robustness.
Wagner shows how evolution by natural selection preferentially finds and favors robust solutions to the problems organisms face in surviving and reproducing. Such robustness, he argues, also enhances the potential for future evolutionary innovation. Wagner also argues that robustness has less to do with organisms having plenty of spare parts (the redundancy theory that has been popular) and more to do with the reality that mutations can change organisms in ways that do not substantively affect their fitness.
Unparalleled in its field, this book offers the most detailed analysis available of all facets of robustness within organisms. It will appeal not only to biologists but also to engineers interested in the design of robust systems and to social scientists concerned with robustness in human communities and populations.
"Wagner's treatise is more than good biology; it is also very interesting biology. The picture is painted by talented hands. . . . If I have a favorite aspect of the book, it is the meticulous yet insightful analysis of neutral spaces and their relevance for the main themes of the book."--Eörs Szathmáry, Nature
"Wagner contributes significantly to the emerging view that natural selection is just one, and maybe not even the most fundamental, source of biological order. His two-page epilogue throws out seven open questions for systems biologists and neo-Darwinians to consider; hopefully they will do so."--Greg Gibson, Science PART I: ROBUSTNESS BELOW THE GENE LEVEL 13 Chapter 2: The Genetic Alphabet 15 PART II: ROBUSTNESS ABOVE THE GENE LEVEL 91 Chapter 7: Regulatory DNA Regions and Their Reorganization in Evolution 93 PART III: COMMON PRINCIPLES 193 Chapter 13: Neutral Spaces 195 PART IV: ROBUSTNESS BEYOND THE ORGANISM 295 Chapter 19: Robustness in Natural Systems and Self-Organization 297
Acknowledgments xiii
Chapter 1: Introduction 1
Chapter 3: The Genetic Code 25
Chapter 4: RNA Structure 39
Chapter 5: Proteins and Point Mutations 62
Chapter 6: Proteins and Recombination 78
Chapter 8: Metabolic Pathways 104
Chapter 9: Metabolic Networks 120
Chapter 10: Drosophila Segmentation and Other Gene Regulatory Networks 143
Chapter 11: Phenotypic Traits, Cryptic Variation, and Human Diseases 161
Chapter 12: The Many Ways of Building the Same Body 175
Chapter 14: Evolvability and Neutral Mutations 217
Chapter 15: Redundancy of Parts or Distributed Robustness? 228
Chapter 16: Robustness as an Evolved Adaptation to Mutations 247
Chapter 17: Robustness as an Evolved Adaptation to Environmental Change and Noise 270
Chapter 18: Robustness and Fragility: Advantages to Variation and Trade-offs 281
Chapter 20: Robustness in Man-made Systems 310
Epilogue: Seven Open Questions for Systems Biology 321
Bibliography 323
Index 359