April 1, 2021

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This article was originally published as a chapter in the book “Design and Catastrophe: 51 Scientists Explore Evidence in Nature"

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During the winter months of 1869, the Swiss doctor Friedrich Miescher was hard at work in his laboratory at the University of Tübingen. He was studying the chemical composition of cells in pus-soaked surgical bandages that he had retrieved from the hospital garbage. There, he discovered a new microscopic substance that was not a protein or a lipid. Since the substance originated in the nucleus of the cells, he called it “nuclein.” Dr. Miescher even wondered whether this substance might be responsible for the traits that organisms inherit from their parents, but later dismissed this idea.[1]

It would take another 75 years before Francis Crick and James Watson would shine their X-ray spotlights along the coiled strands of nuclein and claim a Nobel Prize for figuring out the double helix structure of one of the world’s most iconic molecules: deoxyribonucleic acid (DNA).

While the discovery of DNA and its structure is scientifically exhilarating, what it encodes is even more stunning. DNA literally contains the code for all of life on Earth. It reveals that life is not just physics and chemistry, but also includes information at its most basic level. As Richard Dawkins has observed,

After Watson and Crick, we know that genes themselves, within their minute internal structure, are long strings of pure digital information. What is more, they are truly digital, in the full and strong sense of computers and compact disks, not in the weak sense of the nervous system. The genetic code is not a binary code as in computers, nor an eight-level code as in some telephone systems, but a quaternary code, with four symbols. The machine code of the genes is uncannily computerlike.[2]

In short, DNA functions as an information system that encodes, stores, and retrieves the information needed for life itself.

One of the most fundamental features of an information system is that it uses an alphabet to encode information. DNA is no exception. In particular, it uses four nucleotides called adenine, cytosine, thymine, and guanine, which are represented by the letters A, C, T, and G. This alphabet is so fundamental and firmly established in our genetic thinking that we hardly give it a second thought.

However, I would like to invite you to stop and reflect on this alphabet for a while. We all know of other alphabets, such as the binary alphabet used in computer systems, which uses 0’s and 1’s, and the English alphabet which has twenty-six letters. The question that immediately springs to mind is this: why does the genetic alphabet have four nucleotide letters?

The Hungarian theoretical evolutionary biologist Eörs Szathmáry asked that very question.[3] By undertaking an information-theoretic study of the genetic information system, he was able to show that a four-letter genetic alphabet is optimal with respect to a compromise between two factors: copying fidelity and catalytic efficiency. As the size of the genetic alphabet increases, the catalytic efficiency increases. However, as the alphabet size increases, the copying fidelity decreases. Thus, Szathmáry proposed that the genetic alphabet is a frozen evolutionary optimum from the hypothesized RNA world in which life was supposed to have originated.[4] One is tempted to observe that the term “frozen evolutionary” is an oxymoron. It is reassuring to know, though, that the alphabet that encodes everything about us, together with Aardvarks, Bobcats, Coyotes, and so on, all the way down to Zebras, really is optimal.

Even though our genetic alphabet does seem rather frozen in our biosphere, it raises the question whether it could have been otherwise. Indeed, biochemists have been actively pursuing the possibility of expanding the genetic alphabet, and in February 2019, Steven Benner and a broad team of researchers achieved just that. They expanded the genetic alphabet from four to eight. By making small adjustments to the molecular structure of the standard nucleotides, they were able to create four new nucleotides, which they represented by the letters S, B, P, and Z.[5]

Benner’s expanded genetic alphabet shows that the standard genetic alphabet is not the only one physically possible. So where did it come from originally?

There are four explanations for the origin of the genetic alphabet:

1. It is physically necessary for the genetic alphabet to have four nucleotide letters. The research work of Benner and his team in expanding the genetic alphabet has demonstrated that this explanation is not true.[6]
2. The genetic alphabet contains four nucleotide letters by chance. The information-theoretic research work of Szathmáry has demonstrated that the size of the genetic alphabet is optimal and the probability that the optimal four-letter alphabet would be landed on simply by chance is vanishingly small. Other explanations are therefore more likely to be true.
3. The four-letter genetic alphabet evolved. The difficulty with this explanation is that there is no empirical evidence that the genetic alphabet evolved. Evolution requires a self-replicating mechanism, but this requires an information system that is based on an alphabet. There is no evidence that any protogenetic alphabet existed. Therefore, for the genetic alphabet to evolve, it would have required some form of chemical evolution process. It must be emphasized, though, that we have no empirical evidence of this chemical evolution process. It is fair to say that all chemical evolutionary explanations for the origins of life have reached an impasse.
4. The genetic alphabet was intelligently designed. Like every other alphabet that we know of, including the expansion of the genetic alphabet that Benner and colleagues have achieved, this is the most satisfactory explanation for the genetic alphabet.

As he went about his experiments in Tübingen in 1869, Miescher stumbled upon the molecule that stores the information of life. At the very foundation of this information is an alphabet that points beyond its empirical letters to the Designer of life itself.

NOTES

[1] R Dahm. Discovering DNA: Friedrich Miescher and the early years of nucleic acid research. Human Genetics 2008; 122(6):565–581.

[2] R Dawkins. River out of Eden: a Darwinian view of life. New York: Basic Books; 1995, p. 17.

[3] E Szathmáry. Why are there four letters in the genetic alphabet? Nature Reviews Genetics 2003; 4(12):995–1001.

[4] E Szathmáry. Four letters in the genetic alphabet: a frozen evolutionary optimum? Proceedings of the Royal Society B–Biological Sciences 1991; 245(1313):91–99.

[5] S Hoshika, NA Leal, M-J Kim, M-S Kim, NB Karalkar, H-J Kim, AM Bates, NE Watkins Jr., HA SantaLucia, AJ Meyer, et al. Hachimoji DNA and RNA: a genetic system with eight building blocks, Science 2019; 363(6429): 884–887.

[6] M Warren. 4 new DNA letters double life’s alphabet. Nature 2019; 566:436.

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Sven Östring is director of church planting for the NNSW Conference of Seventh-day Adventists, Australia. He holds a PhD in Computer Networking from the University of Canterbury. He has published articles on Big Bang cosmology in the Journal of the Adventist Theological Society and missional apologetics in the Journal of Adventist Mission Studies. His research interests include comparing warrant in Adventist and scientific epistemology and identifying effective ways of communicating the truth and attractiveness of the Adventist theological system.