Information in the Cell

DNA is a code. Codes come from somewhere.

When Darwin wrote On the Origin of Species in 1859, the cell was thought to be, in his words, “a simple little lump of homogeneous and structureless protoplasm.” The mechanism of inheritance was unknown — Gregor Mendel’s pea experiments would not be published for seven more years, and the structure of DNA was a century away.

It is hard, today, to overstate how wrong the simple-blob picture turned out to be. A single human cell contains, in its nucleus, roughly three billion base pairs of DNA — about \(7.5 \times 10^{8}\) bytes of digital information, depending on how you compress it.¹ The DNA encodes proteins by a four-letter alphabet (A, T, C, G) read in three-letter words (codons) that map to amino acids by a code that is universal across all known life. The cell contains machinery — ribosomes, polymerases, error-checking enzymes — that reads, copies, and repairs the code with an error rate of roughly one mistake per billion base pairs.

It is, in a precise sense, a digital information-processing system. It is the only digital information-processing system in human experience that we did not design.

The information question

The question this raises is sharp. Every other instance of complex, specified, digital information that we have ever traced to a source has turned out to come from a mind. Books, software, the message on a billboard, the spec sheet for an aircraft engine. There is no counter-example.

The Christian-design argument is not DNA is complicated, therefore God. It is something more specific. It is:

1. The cell runs on what is, by every formal measure, a digital code — symbols with meaning, an alphabet, a syntax, error- correction.
2. Every other digital code whose origin we know was authored by a mind.
3. We do not currently have a credible mechanism by which the functional information in the first cell could have arisen by undirected chemistry.
4. Therefore the design inference is, at minimum, a serious candidate explanation.

I want to be careful with (3). There is a large and active field called origin of life research, and it has produced real progress on isolated subproblems — RNA self-replication in narrow lab conditions, plausible synthesis of some prebiotic building blocks. But the central question — how do you get from a soup of small molecules to a self-replicating, information-encoding system — has not been solved, and the leading researchers in the field say so openly. Eugene Koonin, no theist, has called the origin of the first genetic system “a major enigma.”²

What this is not

It is not the argument that natural selection is impossible. Natural selection does what natural selection does — within an existing information-bearing system, it can refine and recombine. The information-origin question is upstream of natural selection. You cannot have variation-and-selection until you have something that can vary and select. That something is what is in question.

It is also not the argument that gaps in our knowledge prove God. I do not want to make a god-of-the-gaps move. The point is not that we don’t know how the cell got here; the point is that we do know something about how information gets here. Every time. And the answer has always been a mind.

What is going on, in plain language

The cell, considered as an engineering problem, has the signature of design. Not a vague aesthetic impression of design. The specific, formal features that we use, in every other context, to identify designed systems:

• A symbolic encoding (DNA → mRNA → protein)
• A translation table (the genetic code)
• Error-correction machinery
• Hierarchical regulation (genes turn other genes on and off)
• Modular reuse (the same domains appear in different proteins)
• Forward error tolerance (silent mutations, redundancy)

If we saw this signature anywhere else — say, on the surface of a distant planet — we would not hesitate to call it a designed system. We would publish a paper. We would, in fact, be looking for the designer.

That we hesitate to draw the same inference inside the cell is, I think, a matter of philosophical commitment, not a matter of evidence.

What this gets you

Like the fine-tuning argument, the information-in-the-cell argument does not, by itself, get you to the God of the Bible. It gets you to a designer — to the conclusion that the cell, considered honestly, looks like something that was made.

The next step — who the designer is, what he has said, whether he is the kind of being you can know — has to come from somewhere else. That somewhere else is the history section.