From: http://www.arn.org/docs/newman/rn_artificiallife.htm

Artificial Life (AL) is a rather new scientific discipline, which didn't really get going until the 1980s.1 Unlike biology, it seeks to study life not out in nature or in the laboratory, but in the computer.2 AL seeks to mimic life mathematically, and especially to generate known features of life from basic principles (Langton, 1989b, pp 2-5). Some of the more gung-ho specialists in AL see themselves as creating life in the electronic medium (Ray, 1994, p 180); others think they are only imitating it (Harnad, 1994, pp 544-49). Without addressing this particular question, theists can at least agree that life does not have to be manifested in biochemistry.

In the late 1940's eminent mathematician and physicist John von Neumann had become interested in the question of whether a machine can self-replicate, that is, produce copies of itself. Von Neumann wished to investigate the logic necessary for replication - he was not interested, nor did he have the tools, in building a working machine at the bio-chemical or genetic level. Remember that at the time DNA had not yet been discovered as the genetic material in nature.