"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.