What does it mean to be alive? You breathe air? You could make a more a convincing case that your alive by your behavior. How you respond to different situations and do things that you couldn’t have predicted in advance. You also act independently. But being alive is essentially a matter of patterns and processes, which is the driving force behind the growing field of artificial life. AL researchers look for the

Distinctive behaviors of living things, and try to create software simulations, that perform these behaviors without being told what to do.

First of all the AL researchers need to create an environment for the species to live. They need individuals populate it, and rules for them to follow. Each individual is built to act independently. Think about yourself for a minute. Do you think that humans are too sophisticated to be represented by a computer model? We spend a large amount of our time obeying rules. All the rules can be easily translated to if-then type rules. A good example of AL can be seen in a simulation called Sugarscape.

Below is a picture of the sugarscape environment.

Sugarscape was created by computer scientist Robert Axtell and social scientist Joshua Epstein of the Brookings Institution in Washington DC. The Sugarscape environment consists of a 50 x 50 grid. Sugar is represented by the yellow dots. The more sugar a cell contains the dark the yellow is. The red and blue dots representing people or families move around the digital landscape in search of food--sugar. Whether they live or die depends on whether they find enough food to satisfy their "metabolic" needs. The dots, or "agents", are given a range of abilities--such as how far they can "see" over their virtual lands searching for food--and are programmed to obey certain rules. In the most basic scenario, the agents look for the richest source of sugar, and go there to eat it. But they are in competition with each other and with groups of agents programmed with different rules and abilities. By modifying the rules governing how the agents interact, Axtell and Epstein make them either fight or cooperate. They can allow the agents to accumulate wealth, excess sugar, and watch health (how much sugar they eat). Disease can also be added and spread through the population by interaction. Reproduction allows the agents pass on their abilities--and the rules they obey--to their offspring. They can create seasons by fluctuating the levels of sugar between areas, which leads to migration. Normally the weaker are weeded out, but if inheritance rules are added those with weaker vision can survive very well off the wealth of a rich parent. They can change on of the sugar areas to spice, and give the agents different metabolic rates and preferences between the two substances, and cause the agents to initiate trade. There is also a maximum number of agents that can live in any one model based upon the amount of sugar. This relates to the carrying capacity of earth. Carrying capacity is the density of population it can sustain. Sugarspace allows for the development of rules for all aspects of our lives. Using Sugarspace, scientists hope to discover what happened to societies in our history.

To watch simulations on Sugarscape, check out these sites:

http://www.discovery.com/area/science/life/digitalplayroom.html

http://www.brookings.org/SUGARSCAPE/movies.htm

Reference:

• The Detroit News, "Computers are the labs in the search for answers to human behaviors" (March 17, 1997)
• Byte, "Chaos Manor: Of Supercomputers, Sound Files, and Sugarscape" (June 1997)
• Discovery Channel Online, "Its Alive" and the Digital Playroom (January, 1997)
• Science News Magazine, "The Gods of Sugarscape" (November 23, 1996)