Abstract
We present a novel stringmol-based artificial chemistry system modelled on the universal constructor architecture (UCA) first explored by von Neumann. In a UCA, machines interact with an abstract description of themselves to replicate by copying the abstract description and constructing the machines that the abstract description encodes. DNA-based replication follows this architecture, with DNA being the abstract description, the polymerase being the copier, and the ribosome being the principal machine in expressing what is encoded on the DNA. This architecture is semantically closed as the machine that defines what the abstract description means is itself encoded on that abstract description. We present a series of experiments with the stringmol UCA that show the evolution of the meaning of genomic material, allowing the concept of semantic closure and transitions between semantically closed states to be elucidated in the light of concrete examples. We present results where, for the first time in an in silico system, simultaneous evolution of the genomic material, copier and constructor of a UCA, giving rise to viable offspring.
Highlights
The term semantic closure, introduced by Pattee [1], refers to the concept that a system can enclose its meaning within itself
We have presented a novel stringmol system modelled on the universal constructor architecture (UCA) first explored by von Neumann [6]
The stringmol UCA system has demonstrated the concept of semantic closure by evolving the meaning of its genomic material, transitioning from one semantically closed state to another
Summary
The term semantic closure, introduced by Pattee [1], refers to the concept that a system can enclose its meaning within itself. The authors conclude from their initial observations that their hand-designed seed has not been displaced by any mutation that preserves the UCA, but mutations that give rise to self-copiers are common [13,15] While both the Avida- and Tierra-based implementations of the UCA successfully implement the architecture of semantic closure, the designs are brittle, albeit in a different way from von Neumann’s: the offspring are not ‘sterile’, they merely abandon the UCA for the simpler strategy of reproduction by self-inspection. We conjecture that under mutation this chemistry will not demonstrate transitions between semantically closed states because the genotype– phenotype mapping is directly encoded: the genotype is the phenotype ‘in quotes’ with the minus form being the passive genotype (‘[]2’), and expression is the process of changing the minus to a plus (‘[]þ’) to get the active phenotype of whatever is in the brackets, leaving no possibility of an alternative interpretation of the genotype. We observe evolution of the stringmol UCA and numerous demonstrations of semantic closure, involving transitions between semantically closed states
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