"It is highly unlikely that the earliest self-reproducing molecules, from which all living oganisms are supposed to have been derived, were capable of universal contruction, and we would not want to eliminate those from the class of truly self-reproducing configurations."


Chris Langton, often called the "father of artificial life" worked to build computer systems that had the properties of life. To this end he built a set of what he called "loops" (resembling a square with a short tail on one end) , and placed them in a sea of zero-state cells. These loops had three layers, like a flattened wire. The outer layers, the insulation, were strings of cells in state 2. These were the sheath cells. They acted as insulation to the core cells, which were like the copper part of the wire, and conducted the data necessary for reproduction. With each generation, the cells in this inner layer followed rules that affected the state of their neighbours, and in effect propagated signals inside the genetic stream of the core.

Langton wanted to arrange the various states so that, following a given rule table dictating the cell's behaviour in the next generation, the tail would become a constructing appendage. It would thrust outward until it reached the desired length, turn the corner,and repeat the process until it completed the square. Once the outer shape of the newly formed loop resembled the parent loop, the flow in the core layer would continue. The "fluid" would be the cell states holding uninterpreted data. When the information was completely passed to the offspring loop, the two loops would separate. Soon after, the signals would change the configuration of the offspring's core so it resembled the initial configuration of the original loop, they would be identical. When the process began again, the unread data would finally be interpreted. A new generation would be born.

Langton was confident that this reproductive behaviour was similar to that of real creatures. In loop reproduction, there was a genotype - a series of core cells that contains genetic code and is copied into the next generation, and there was a phenotype - a coded series of instructions that produces a new organism. This allowed the possibility of evolution (a mutation in the genotype could result in a phenotype with improved fitness whose ability to spread its genes would benefit from the advantage). The process would be, literally, the same as in real organisms, and the evolution would not be simulated, but genuine.

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