Complexity_ A Guided Tour - Melanie Mitchell [4]
Many thanks to the following people for answering questions, commenting on parts of the manuscript, and helping me think more clearly about the issues in this book: Bob Axelrod, Liz Bradley, Jim Brown, Jim Crutchfield, Doyne Farmer, Stephanie Forrest, Bob French, Douglas Hofstadter, John Holland, Greg Huber, Ralf Juengling, Garrett Kenyon, Tom Kepler, David Krakauer, Will Landecker, Manuel Marques-Pita, Dan McShea, John Miller, Jack Mitchell, Norma Mitchell, Cris Moore, David Moser, Mark Newman, Norman Packard, Lee Segel, Cosma Shalizi, Eric Smith, Kendall Springer, J. Clint Sprott, Mick Thomure, Andreas Wagner, and Chris Wood. Of course any errors in this book are my own responsibility.
Thanks are also due to Kirk Jensen and Peter Prescott, my editors at Oxford, for their constant encouragement and superhuman patience, and to Keith Faivre and Tisse Takagi at Oxford, for all their help. I am also grateful to Google Scholar, Google Books, Amazon.com, and the often maligned but tremendously useful Wikipedia.org for making scholarly research so much easier.
This book is dedicated to Douglas Hofstadter and John Holland, who have done so much to inspire and encourage me in my work and life. I am very lucky to have had the benefit of their guidance and friendship.
Finally, much gratitude to my family: my parents, Jack and Norma Mitchell, my brother, Jonathan Mitchell, and my husband, Kendall Springer, for all their love and support. And I am grateful for Jacob and Nicholas Springer; although their births delayed the writing of this book, they have brought extraordinary joy and delightful complexity into our lives.
PART I
Background and History
Science has explored the microcosmos and the macrocosmos; we have a good sense of the lay of the land. The great unexplored frontier is complexity.
—Heinz Pagels, The Dreams of Reason
CHAPTER 1
What Is Complexity?
Ideas thus made up of several simple ones put together, I call Complex; such as are Beauty, Gratitude, a Man, an Army, the Universe.
—John Locke, An Essay Concerning Human Understanding
Brazil: The Amazon rain forest. Half a million army ants are on the march. No one is in charge of this army; it has no commander. Each individual ant is nearly blind and minimally intelligent, but the marching ants together create a coherent fan-shaped mass of movement that swarms over, kills, and efficiently devours all prey in its path. What cannot be devoured right away is carried with the swarm. After a day of raiding and destroying the edible life over a dense forest the size of a football field, the ants build their nighttime shelter—a chain-mail ball a yard across made up of the workers’ linked bodies, sheltering the young larvae and mother queen at the center. When dawn arrives, the living ball melts away ant by ant as the colony members once again take their places for the day’s march.
Nigel Franks, a biologist specializing in ant behavior, has written, “The solitary army ant is behaviorally one of the least sophisticated animals imaginable,” and, “If 100 army ants are placed on a flat surface, they will walk around and around in never decreasing circles until they die of exhaustion.” Yet put half a million of them together, and the group as a whole becomes what some have called a “superorganism” with “collective intelligence.”
How does this come about? Although many things are known about ant colony behavior, scientists still do not fully understand all the mechanisms underlying a colony’s collective intelligence. As Franks comments further, “I have studied E. burchelli [a common species of army ant] for many years, and for me the mysteries of its social organization still multiply faster than the rate at which its social structure can be explored.”
The mysteries of army ants are a microcosm for the mysteries of many natural and social systems that we think of as “complex.” No one knows exactly how any community