Charles Darwin showed how "organs of extreme perfection and complication, which justly excite our admiration" arise not from God's foresight by from the evolution of replicators over immense spans of time. Freeman Dyson reminds us that life consists of both metabolism and replication, and that the two may have started separately. (In its pure state, replication can only be parasitic.) He subscribes to Lynn Margulis' theory that RNA is the oldest and most incurable of our parasitic diseases. (see prokaryote / eukaryote) Genetics is concerned with the replication and variation of of genes in a population (and their impact on adaptation. (See genotype / phenotype )
John von Neumann proved that a machine could be designed that could replicate itself. The logical problem is how to avoid infinite regress that would require the instructions: "how to build machine (how to build machine (how to build machine (etc.)))" If the instructions merely stated "how to build the machine" it would work once and then stop. The new machine would be unable to replicate itself.
The self-replicating machine requires a certain threshold of complexity with a controller that is able to use the same instructions for its own operation as well as for replication. Thinking of the instructions as a "blueprint" the machine is both able to carry out the instructions and copy them as separate operations. (cf. the distinction between use and mention in language?) The subsequent discovery of the mechanism of DNA, which also works in two distinct modes, provided a fundamental link between theories of automata, the development of computers, and the study of life. (The computer industry took up von Neumann's ideas, giving them the names hardware and software -- a distinction similar to that between metabolism and replication)
For this reason, computers are Von Neumann machines. They are able to use the same coded messages either as memory or in the operation of their central processing units. This is called a subroutine, which stores intermediate values in a task and the logic of the program such that a problem can be solved serially.
Parallel processing differs from serial processing and is the model for complex systems.
The possibility of self-replication is the main bridge to the transformation of technology into life, and is one of the central themes of the path "human/posthuman"
Manuel De Landa's study of War in the Age of Intelligent Machines starts with the speculation that one day "robot historians" might study the technological lineages that had lead to generations of killer robots.(cf Terminator)In this point of view, humans would have served only as machines' surrogate reproductive organs until robots acquired their own self-replication abilities. (see intro pp 1-11)
See also automata, A-life, self-reproducing factories in intelligent building
In Engines of Creation, K. Eric Drexler describes some of the potential technologies that use replicator/assemblers at the molecular level.