The Simplest Self-Replicator
Developing Insights into the Design of the Simplest Self-Replicator (SSR) and its Complexity
Our goal is to investigate the internal design of a hypothetical Simplest possible Self Replicator (SSR) modeled after a single cell organism. We start from a simple set of assumptions regarding the exchanges of the SSR with its environment: intake of materials for internal processes, element construction and energy generation and output of refuse materials. There are only two requirements for the SSR: to have an enclosure and to be capable of creating an identical copy of itself. The focus of the investigation is a concrete, material SSR, not an abstraction like cellular automata or a software or simulated artifact. Our approach is to take an empirical, deductive approach and in a logical manner identify step by step the elements and functions that, by necessity, must be part of the SSR.
There is a good amount of research about the self-replication and self-replication machines and artifacts. John Von Neumann founded the field of self-replicating machines and described self-replication with cellular automata (1). W.M. Stevens studied simulation environments for self-replication (2). NASA Advanced Automation for Space Mission study (1980) – particularly relevant for our interests - is an expanded engineering study covering the organization, the parts and relationships of a lunar facility that would start from some seed machinery and able to fabricate replicas of itself (3).
We develop the SSR design by first identifying the distinct nature of the elements and components that must exist inside the SSR and their unique role in the SSR architecture. We then develop a list of functions and capabilities that must operate inside SSR in order to fabricate step by step the elements of the growing “daughter” SSR. We identify internal capabilities needed for its parts and assemblies construction like: the ability to store and use the design of the inner parts of the SSR, the ability to store and use both a “bill of materials” and a “body plan”. Farther analysis takes us to the realization that the SSR must exhibit advanced, diverse fabrication capabilities based on significant information representation, codification, storage, retrieval, and information processing capabilities. The SSR must also possess significant sensory, status representation and control capabilities.
Another objective is to use the SSR design we achieved to reflect upon its revealed complexity. In order to get a more concrete understanding of the SSR complexity we ask and try to answer a few hypothetical questions. How difficult or feasible will be to implement the enumerated SSR fabrication or computational capabilities within a concrete SSR with the scale of a single cell organism? What if we increase the scale 10, 1000, 1000000 times? Can the most advanced multi-disciplinary engineering labs build a real SSR with today most advanced technologies?
(1) John von Neumann and Arthur W Burks. Theory of Self-Reproducing Automata. University of Illinois Press, Urbana, Illinois, 1966.
(2) W.M. Stevens. Self-Replication, Construction and Computation, PhD Thesis, The Open University, 2009
(3) Advanced Automation for Space Missions, NASA, 1980, http://www.islandone.org/MMSG/aasm/