Complexity_ A Guided Tour - Melanie Mitchell [58]
However, you may have noticed something I have so far swept under the rug. There is a major difference between my self-copying program and DNA self-reproduction. The self-copying program required an interpreter to execute it: an instruction pointer to move down the lines of computer code and a computer operating system to carry them out (e.g., actually perform the storing and retrieving of internal variables such as ip and L, actually print strings of characters, and so on). The interpreter is completely external to the program itself.
In contrast, in the case of DNA, the instructions for building the “interpreter”—the messenger RNA, transfer RNA, ribosomes, and all the other machinery of protein synthesis—are encoded along with everything else in the DNA. That is, DNA not only contains the code for its self-replicating “program” (i.e., the enzymes that perform the splitting and copying of DNA) but also it encodes its own interpreter (the cellular machinery that translates DNA into those very enzymes).
Von Neumann’s Self-Reproducing Automaton
Von Neumann’s original self-reproducing automaton (described mathematically but not actually built by von Neumann) similarly contained not only a self-copying program but also the machinery needed for its own interpretation. Thus it was truly a self-reproducing machine. This explains why von Neumann’s construction was considerably more complicated than my simple self-copying program. That it was formulated in the 1950s, before the details of biological self-reproduction were well understood, is testament to von Neumann’s insight. Von Neumann’s design of this automaton and mathematical proof of its correctness were mostly completed when he died in 1957, at the age of 53, of cancer possibly caused by his exposure to radiation during his work on the atomic bomb. The proof was completed by von Neumann’s colleague, Arthur Burks. The complete work was eventually published in 1966 as a book, Theory of Self-Reproducing Automata, edited by Burks.
John von Neumann, 1903–1957 (AIP Emilio Segre Visual Archives)
Von Neumann’s design for a self-reproducing automaton was one of the first real advances in the science of artificial life, demonstrating that self-reproduction by machine was indeed possible in principle, and providing a “logic” of self-reproduction that turned out to have some remarkable similarities to the one used by living systems.
Von Neumann recognized that these results could have profound consequences. He worried about public perception of the possibilities of self-reproducing machines, and said that he did not want any mention of the “reproductive potentialities of the machines of the future” made to the mass media. It took a while, but the mass media eventually caught up. In 1999, computer scientists Ray Kurzweil and Hans Moravec celebrated the possibility of super-intelligent self-reproducing robots, which they believe will be built in the near future, in their respective nonfiction (but rather far-fetched) books The Age of Spiritual Machines and Robot. In 2000 some of the possible perils of self-reproducing nano-machines were decried by Bill Joy, one of the founders of Sun Microsystems, in a now famous article in Wired magazine called “Why the Future Doesn’t Need Us.” So far none of these predictions has come to pass. However, complex self-reproducing machines may soon be a reality: some simple self-reproducing robots have already been constructed