Reviews elsewhere on the web:
Suasn Stepney
Francis Fukuyama
Alan Dorin

Joshua M Epstein and Robert Axtell

Growing artificial societies

Doing experiments in the social sciences isn't easy - you can hardly meddle with a society just to see what happens. But it's possible to create computer models of societies, to see which features lead to realistic societies. This is what Joshua M. Epstein and Robert Axtell have done with their Sugarscape model, and Growing Artificial Societies is a report of some of the things they have observed. The model starts with a landscape in which sugar grows, with agents who roam about collecting sugar which they need to live. Even with such a simple model is it possible to see featues such as migration and uneven wealth distribution.

The model is then extended in various ways, for instance giving the agents various properties which can be passed on to offspring via sexual reproduction. Introduction of another commodoty, spice, allows the possibility of trade, an the authors point out the importance of local interactions, as distinct from believing that there must be a global equilibrium price. Introduction of disease to the model shows the advantages of such a cellular automaton based model, as distinct from models based on differential equations. In the last chapter the authors show what can be seen by putting eveything together, showing that such a model can be an invaluable tool in the social sciences, in particular in showing the links between different fields. There is a CD-ROM to go with the book, and it would be good to see some of the examples, but there is no problem with reading the book on its own. (Some parts of the Sugarscape model can also be found on the internet). I'd recommend this book to anyone wanting to see this new way of approaching the social sciences, as well as to those interested in the programming side of such models.

Amazon.com info
Paperback 228 pages  
ISBN: 0262550253
Salesrank: 401624
Weight:0.97 lbs
Published: 1996 Brookings Institution Press & MIT Press
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Amazon.co.uk info
Paperback 226 pages  
ISBN: 0262550253
Salesrank: 1043880
Weight:0.97 lbs
Published: 1996 Perseus (for Brookings)
Amazon price £29.95
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Amazon.ca info
Paperback 228 pages  
ISBN: 0262550253
Salesrank: 561613
Weight:0.97 lbs
Published: 1996 Brookings Institution Press & MIT Press
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Marketplace:New from CDN$ 32.72:Used from CDN$ 28.31
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Product Description
A Brookings Institution Press and MIT Press publication


How do social structures and group behaviors arise from the interaction of individuals? In this groundbreaking study, Joshua M. Epstein and Robert L. Axtell approach this age-old question with cutting-edge computer simulation techniques. Such fundamental collective behaviors as group formation, cultural transmission, combat, and trade are seen to "emerge" from the interaction of individual agents following simple local rules.


In their computer model, Epstein and Axtell begin the development of a "bottom up" social science. Their program, named Sugarscape, simulates the behavior of artificial people (agents) located on a landscape of a generalized resource (sugar). Agents are born onto the Sugarscape with a vision, a metabolism, a speed, and other genetic attributes. Their movement is governed by a simple local rule: "look around as far as you can; find the spot with the most sugar; go there and eat the sugar." Every time an agent moves, it burns sugar at an amount equal to its metabolic rate. Agents die if and when they burn up all their sugar. A remarkable range of social phenomena emerge. For example, when seasons are introduced, migration and hibernation can be observed. Agents are accumulating sugar at all times, so there is always a distribution of wealth.


Next, Epstein and Axtell attempt to grow a "proto-history" of civilization. It starts with agents scattered about a twin-peaked landscape; over time, there is self-organization into spatially segregated and culturally distinct "tribes" centered on the peaks of the Sugarscape. Population growth forces each tribe to disperse into the sugar lowlands between the mountains. There, the two tribes interact, engaging in combat and competing for cultural dominance, to produce complex social histories with violent expansionist phases, peaceful periods, and so on. The proto-history combines a number of ingredients, each of which generates insights of its own. One of these ingredients is sexual reproduction. In some runs, the population becomes thin, birth rates fall, and the population can crash. Alternatively, the agents may over-populate their environment, driving it into ecological collapse.


When Epstein and Axtell introduce a second resource (spice) to the Sugarscape and allow the agents to trade, an economic market emerges. The introduction of pollution resulting from resource-mining permits the study of economic markets in the presence of environmental factors.


This study is part of the 2050 Project, a joint venture of the Santa Fe Institute, the World Resources Institute, and the Brookings Institution. The project is an international effort to identify conditions for a sustainable global system in the middle of the next century and to design policy actions to help achieve such a system.