Is “biological information” merely an analogy of convenience for biologists, or does the cell contain information in the sense of a language or code? In this series we explore the science behind this question and its implications for the arguments of the Intelligent Design movement.
In 1696, British apologist and author John Edwards published a lengthy treatise on Scripture and natural theology – with the descriptive (if rather wordy) title A Demonstration of the Existence and Providence of God From the Contemplation of the Visible Structure of the Greater and Lesser World. As the title suggests, Edwards was on a mission both to convince skeptics and to shore up the faith of believers using what he viewed as the best science of the day. A significant portion of the book attacks heliocentrism – the hypothesis of Copernicus that the sun, rather than the earth, is the center of the universe and that the earth is in motion around the sun – on both scriptural and scientific grounds. These apologetics arguments were doomed to fail, as we know in hindsight. By 1730, convincing empirical evidence for stellar aberration – the effect of a moving earth on incoming starlight – was available and widely viewed as strong evidence for the Copernican view. Edwards’s apologetic, which had seemed so convincing to him in 1696, had had a shelf life of less than 35 years.
A second argument by Edwards, however, fared much better. Edwards was fascinated by the properties of the sun and stars. In particular, he was taken with their seemingly inexhaustible supply of fuel, for which there was no good scientific explanation in his day (pg. 61):
This stupendous Magnitude argues the Greatness, yea the Immensity and Incomphrensiblenes of their Maker. And if it be ask’d, Whence is that Fewel for those vast Fires, which continually burn? Whence is it that they are not spent and exhausted? How are those flames fed? None can resolve these Questions but the Almighty Creator, who bestowed upon them their Being; who made them thus Great and Wonderful, that in them we might read his Existence, his Power, his Providence…
For Edwards, then, the properties of sun and stars were both beyond the reach of human understanding, and evidence for God’s existence – and the lack of scientific explanation was a key feature in his argument. It would not be until the 1920s and 1930s that the idea of nuclear fusion as the energy source for stars would be hypothesized and tested. This argument of Edwards lasted for over 200 years before it was revealed as flawed.
An interesting question to consider is this: should Edwards have made these arguments part of his apologetic? They were, after all, effective for their time and place, and likely supported the faith of many people before they were revealed by science to be inadequate. The latter argument, in particular, remained viable for hundreds of years. Should Edwards have foregone the opportunity to make a case for God with this approach in light of the possibility that future science might render his arguments null and void? If you had been alive in 1696, would you have wanted to know how these arguments would fare over the coming decades and centuries?
Biological Information: Great and Wonderful
If Edwards had been aware in 1696 of the intricate processes that govern information processing in the cell, he likely would have described them as “great and wonderful” as he did the properties of the stars. And indeed, both processes are great and wonderful, and (in my opinion) do offer a signpost toward the existence of their Creator. Where I differ from Edwards, however, is that I do not consider a scientific understanding of either process as a diminishment of such a view. With my limited understanding of nuclear physics and how it plays out in stars, for example, I am amazed that fusion reactions can produce the heavier elements necessary for life. In my mind, understanding the physical process is all the more reason for worship and wonder.
So too with biological information. As a cell biologist and geneticist, I find the details of how cells perform information processing fascinating. Nor do I find potential scientific explanations for the function or origins of these processes threatening to my faith. While there is much that remains for science to discover about this area, I think it is misguided to use that fact as the basis for arguments defending the Christian faith, as some in the Intelligent Design (ID) movement have done.
In order to evaluate those ID arguments, it will be helpful to have a picture of these processes in mind. Let’s sketch out some of the basic details before we discuss what science knows, and doesn’t know, about the function and possible origins of this elegant set of biochemical reactions.
DNA and Proteins: Archive and Actions
One of the first things that students of biology learn is that DNA functions as a hereditary molecule, but protein molecules perform most of the day-to-day jobs that need doing in the cell. These two types of molecules are especially suited for their particular roles, and neither is capable of performing the other’s role. Examining their particular properties reveals why this is the case.
Both DNA and proteins are polymers, which is just the technical way of saying that they are large molecules made up of repeating units (called monomers) joined together. If you’re familiar with LEGO, the toy building bricks, you can imagine a stack of bricks – say, a stack of 4x4 bricks of different colors. If one 4x4 brick is a “monomer”, then a stack of such bricks is a “polymer”. The different colors can represent the different monomers available – which, in our analogy, refers to the four possible monomers for DNA (the famous A, C, G, and T) or the 20 different monomers found in proteins (known as amino acids).
For DNA, the four monomers each have an interesting property: their chemical structure is physically attractive to one of the other monomers. “A”, for example, is the chemical adenine – which is attractive to “T”, or thymine. Here’s what the chemical structures look like:
In this diagram, adenine (A) is on the left, and it is paired up with a thymine (T) on the right. Solid lines indicate chemical bonds (“covalent” bonds) within the molecules. The two dashed lines, however, show attractions that are not covalent bonds, but a weak attraction called a “hydrogen bond”. Think of hydrogen bonds as weak magnetic attractions holding the two molecules in place relative to each other. Similarly there are hydrogen bonds that form between cytosine (C) and guanine (G).
The importance of these attractions is that one polymer of DNA can act as a template to construct a second polymer simply by matching up the monomers one by one as they are added to a growing chain of DNA (a job done by protein enzymes). It is this feature of DNA that makes it very easy to copy accurately – making it an ideal carrier of hereditary information.
In contrast to the mere four monomers of DNA, proteins are made up of 20 monomers – the amino acids. The molecular shapes of amino acids are much more diverse than for DNA monomers, as can be seen in this sampling of the 20:
The functional importance of this diversity is that proteins of many shapes can be constructed from this set of monomers, whereas all DNA pretty much has the same shape (the famous double helix of two complementary polymers wrapped around each other). The diverse shapes of proteins allow them to do all sorts of biological functions – act as cell structural components, function as enzymes to speed up chemical reactions, and so on. Proteins do many things; DNA does one. Each is very well suited to its role, and neither can do the function of the other. DNA cannot take on the myriad of shapes needed for functional roles in the cell; proteins cannot use their monomers to copy themselves and pass on their information, since amino acids do not pair up with a partner in the way DNA monomers do. Both roles are essential for life as we know it: we can’t live without either.
In the next post in this series, we’ll examine the role of RNA – a molecule that acts as a bridge between the information in DNA, and the structure of proteins. As we will see, this molecule acts as a bridge between these two “languages” because it can carry information like DNA, and fold up to take on functional shapes like proteins.