Biophysicist Hubert Yockey determined that natural selection would have to explore 1.40 x 10^70 different genetic codes to discover the optimal universal genetic code that is found in nature. The maximum amount of time available for it to originate is 6.3 x 10^15 seconds. Natural selection would have to evaluate roughly 10^55 codes per second to find the one that is optimal. Put simply, natural selection lacks the time necessary to find the optimal universal genetic code we find in nature. (Fazale Rana, -The Cell's Design - 2008 - page 177)
Ode to the Code - Brian Hayes
The few variant codes known in protozoa and organelles are thought to be offshoots of the standard code, but there is no evidence that the changes to the codon table offer any adaptive advantage. In fact, Freeland, Knight, Landweber and Hurst found that the variants are inferior or at best equal to the standard code. It seems hard to account for these facts without retreating at least part of the way back to the frozen-accident theory, conceding that the code was subject to change only in a former age of miracles, which we'll never see again in the modern world.
Deciphering Design in the Genetic Code
Excerpt: When researchers calculated the error-minimization capacity of one million randomly generated genetic codes, they discovered that the error-minimization values formed a distribution where the naturally occurring genetic code's capacity occurred outside the distribution. Researchers estimate the existence of 10 possible genetic codes possessing the same type and degree of redundancy as the universal genetic code. All of these codes fall within the error-minimization distribution. This finding means that of the 10 possible genetic codes, few, if any, have an error-minimization capacity that approaches the code found universally in nature.
Collective evolution and the genetic code - 2006:
Excerpt: The genetic code could well be optimized to a greater extent than anything else in biology and yet is generally regarded as the biological element least capable of evolving. http://www.pnas.org/content/103/28/10696.full
The coding system used for living beings is optimal from an engineering standpoint.
Werner Gitt, - In The Beginning Was Information - p. 95
Here, we show that the universal genetic code can efficiently carry arbitrary parallel codes much better than the vast majority of other possible genetic codes.... the present findings support the view that protein-coding regions can carry abundant parallel codes.
The data compression of some stretches of human DNA is estimated to be up to 12 codes thick (Trifonov, 1989). (This is well beyond the complexity of any computer code ever written by man). John Sanford - Genetic Entropy
As well there are additional levels of more nuanced codes associated with manipulating DNA:
Histone Inspectors: Codes and More Codes - Cornelius Hunter - March 2010
Excerpt: By now most people know about the DNA code. A DNA strand consists of a sequence of molecules, or letters, that encodes for proteins. Many people do not realize, however, that there are additional, more nuanced, codes associated with the DNA. For instance, minor chemical modifications (such as the addition of a methyl group) to the DNA provide bar-code like signals to the protein machinery that operate on the DNA. This DNA methylation influences which genes, along the DNA strand, are read off. And this DNA methylation itself may be modified to provide additional information.
Or again, the DNA is wrapped around histone proteins, and these histones are also bar-coded. The histones have a hub, around which the DNA wraps, and a tail that sticks out on which chemical tags are attached. Again these tags are signals for the protein machinery. Furthermore, these tags are removed as well. Such modifications and removal of these chemical tags means that these codes are dynamic, and there are protein inspectors that double-check these complex encodings.
These subtle codes are also context dependent. In one type of cell a histone modification may turn off a gene whereas in another type of cell the same histone modification may turn on the gene.
Histone Variants: The Incredible Story of Gene Regulation
Human DNA is like a computer program but far, far more advanced than any software we've ever created.
Bill Gates, The Road Ahead, 1996, p. 188
The Coding Found In DNA Surpasses Man's Ability To Code - Stephen Meyer - video
Intelligent Design - The Anthropic Hypothesis