Wednesday, 6 April 2011

DNA and the Case of the Bad Metaphor: Now with 100% more Creationist Smackdown!

I love DNA. It is a wonderfully complex molecule and the mechanisms whereby genetic information is stored and accessed is fascinating; and yet, at the same time, the basic premise by which is works - the "central dogma" of molecular biology - is beautifully simple. There is little wonder why DNA has caught the eye of the public in a way that few other biological compounds have. This fascination with DNA has necessitated trying to explain the concepts underlying genetics to the public. Therein lies a problem for scientists and science journalists: how to convey the intricate and often confusing workings of science in a way that is both interesting and easy to understand for the layperson. The one tool brandished about the most is the metaphor. Unfortunately, the metaphor can be dangerous, and there is no better example of this than those metaphors used to explain DNA. Two unfortunate metaphors for DNA have been devised: the idea that DNA functions as a "blueprint" and the idea that DNA functions like a "computer code".

The 'blueprint' metaphor is especially poor. Consider what a blueprint is, exactly. It is a scale schematic used to represent a structure. If you have a blueprint of a hotel, you have a schematic of how to build that hotel. The blueprint tells you everything you need to know - how high the ceilings are, how long each wall is, how many steps are in each flight of stairs. Furthermore, you know that 1 inch on the blueprint represents, say, 1 meter in the actual hotel. From the blueprints, you can precisely construct the hotel. But there is more to a blueprint than this. The information conveyed in a blueprint works both ways - you can use a blueprint to construct a hotel, and from a fully constructed hotel, you can derive a blueprint. If a wall in the hotel is 3m in length, you can draw a wall on the blueprint 3 inches long. The information is reversible. You can go from blueprint to structure and from structure to blueprint.

This is where the analogy with DNA fails. DNA does not work as a blueprint because the information is not reversible. DNA does contain information necessary to construct an organism, but if you examine a fully formed organism, you cannot reconstruct the original DNA sequence. You cannot measure the length of a nose or determine the colour of an eye, and then write out the specific sequence needed to create these features. This is a very important aspect of a blueprint, and DNA does not meet this requirement. Rather, DNA acts more like a recipe. A recipe tells you what ingredients you need and in what manner to combine them in order to create a pie. But if you have a pie, you cannot examine it, even in the most minute of detail, and work out the exact recipe that was used. The information contained in a recipe is not reversible, just as the information spelled out by our genes is not reversible.

The 'computer code' metaphor is also a poor one, for multiple reasons (this particular analogy was popularized by Discovery Institute lackey Stephen C. Meyer). The way a computer code works is that the exact sequence of the code - the precise order of the binary 1s and 0s - spells out exactly what operations the computer must perform. But in genetics, the sequence is only part of the picture. Just as important are genetic regulatory networks - which genes are turned on at what times and in combination with which other genes. Phenotypes are not simply the result of particular gene sequences but the result of specific gene-gene (or gene network-gene network) interactions.

But DNA bears little relation to a "code" in a more fundamental way. Consider exactly what a "code" is. A code is a system of arbitrary symbols used to represent  ideas and objects. In a sense, language itself is a "code"; the symbol "dog" represents that furry tetrapod with a waggly tail, for example. In a code, the symbols themselves have no inherent meaning. The letter "d" is meaningless by itself, as are the letters "o" and "g". It is only in combination that they derive meaning, and their meaning is derived from the idea that they represent. Furthermore, they only have meaning because we give them meaning. "Dog" is merely the label we apply to Fido; in a universe without sentient beings, "dog" would be meaningless. DNA does not fit this description at all. DNA is not arbitrary in any way; each letter of the genetic "code" is an actual biological compound. ACCGTCGA might be the gene for determining how long your toe hair is, but unlike a code, A, C, T and G each have their own non-arbitrary meaning. And this meaning exists independently of human sentience - the sequence of nucleotides does not have meaning only because we give it meaning. It would have meaning even if humans didn't exist at all.

What DNA is, is a polymeric chemical that follows a dynamic chemical process, governed by universal physical rules. It is only a "code" in the same sense that nuclear fusion is a "code" for how stars produce light

So why am I taking the time to mention these things? The reason is because both these weak metaphors have been abused time and time again by creationists (and particularly the Intellignent Design IDiots). Just recently, the video below was posted to Youtube by Nephilimfree, who you may recall from my last blog post (to which he made no attempt to refute, despite having been made aware of my critique - something that should probably come as no surprise to anyone, given the tendency for creationists to retreat with tail planted firmly between their legs when presented with cold, hard, scientific fact). This latest video does not appear to be made by Nephy himself (though he gives no credit to the video's creator), but is nonetheless filled to the brim with that Nephy-brand distortion of science. While it is significantly shorter than his last few 14-minute diatribes, it might still result in significant impairment to your mental faculties, so watch at your own risk.

The video wastes no time in misleading the viewer, tossing out the "blueprint" metaphor 39 seconds in: "DNA contains the blueprint of all life and is by far the densest information storage mechanism known in the universe".  For reasons stated above, we know this metaphor is misleading at best and deceptive at worst. But it continues: "The program code and design of such an incredible system indicated a supremely intelligent designer".

Now, a claim like that one is pretty bold, and would require pretty strong evidence to rationally accept it as fact. So what kind of evidence does the video provide? The answer, really, is "none". It immediately cuts to clips of creationist talking heads (Ken Ham, Dave Hunt, and the like) who reiterate one point: "DNA is a code, and codes are information, which only comes from intelligence". Yet, at no point do they present one shred of evidence for why this is the case. They expect the viewer to simply take what they say as being true. Here we have a major distinction between science and creationism - any scientific claim will be backed up by evidence and cite sources explaining why the claim is true, whereas creationism makes assertions which they simply expect you to believe.

The video proceeds to give some details of DNA - it is self-replicating, has error-correction mechanisms ("there are special proteins called enzymes...making repairs" announces Frank Sherwin - a statement that could only be more generic had he said "there are chemicals that do stuff"), etc. But throughout, a unifying theme is repeated - "these things are complex and only God can produce complexity". But again, they provide no reason why we should believe this is true. Perhaps it is left up to our imagination.

What the video boils down to is that creationists make two claims about DNA: 1) that DNA is a "code", and 2) information/complexity (via the genetic code) can only come from an intelligent designer. Both these claims are really nonsense.

Calling DNA a "code", as explained above, is simply incorrect. DNA is not a code in any sense of the word. But let's assume for a moment, that DNA is a code written by God. If this were the case, then God could definitely benefit from taking an introductory computer programming course. God seems to be an awful coder. DNA is very error prone, and the code is regularly mistranslated and copied incorrectly. Different organisms have similar functions, but use different coding sequences. Some organisms contain the code for functions they don't even use, and the majority of code in any given organism is completely non-coding! For an all powerful supreme being, his code is awfully amateurish.

The argument that "information and complexity can only come from intelligence" is also absurd. To begin with, whenever creationists fling around the term "information" they never define what it is they mean by the term. "Information" can mean different things in different contexts. To a creationist, information is some amorphous concept, never, or only vaguely, defined. The idea that "information" cannot be arranged by nature is also silly. Consider the following situation. A friend says to you, "The sun has to have been created by an intelligent creator. There is no other way to explain sunlight." "Don't be silly," you retort. "The sun is a burning ball of hydrogen which emits energy with wavelengths in the visible spectrum." Unfazed, your friend replies, "That is nonsense. Consider the sources of light we have here on Earth. We only ever see light from light bulbs. Light bulbs do not arise naturally! They are the produce of man made design. We never see light occurring naturally. The sun has to have been intelligently designed. Chemicals cannot just come together and "randomly" create light!". Such an argument is not unlike that creationists use to explain genetic information. They claim that genetic information has to have been designed because information does not arise spontaneously; but the claim that information does not arise spontaneously assumes that genetic information was designed! Once again, a creationist argument is little more than tautology.

In the end, the argument presented in Nephy's little video can basically be paraphrased as "Look at DNA! Look at it! Isn't it complex?! And look at cells! They are soooooo complex!", and then baselessly ascribing that complexity to God. This is, of course, patently untrue. There are many examples of complexity arising through completely naturalistic mechanisms. Snowflakes are a perfect example of this. Do creationists really think that their God spends time making each individual snowflake? What about crystals? Pour some sugar into hot water and suspend a string in it, and before long, you have beautiful and complex crystalline growth. This is an entirely natural process - complexity without the intelligence.

Complexity is not the hallmark of design. DNA is not a blueprint nor is it a computer code. And once again, Nephilimfree is not correct.

1 comment:

Anonymous said...

Ok, creationism is BS, granted.

But I don't think one can quite dismiss the "code" analogy without diverting from mainstream/actual science.

We speak of things like codons (which sort of a biological-latin thing for "coders"), "non coding DNA", and I think that I've seen an argument/explanation that even at the basic level of codons it satisfies some formal definitions of a "code." Things like a certain level of "arbitrarity" in the "definition". Even though it's just chemistry, the causal chain ins't as direct as that of a simple reaction (so, it's not like the "code" of the nuclear reaction or a chemical "code" in the generation of foam from vinegar and sodium bicarbonate). There's a whole complex "chemical context" that defines that a given aminoacid is coded by a given codon or its synonyms.

Scientists even speak of the "evolution of the genetic code", which is still quite obscure, it's just not like there was the "primordial soup", and then, as unsurprisingly as water and earth form mud, DNA formed and started to replicate itself and evolve.

I'm not trying to defend any sort of creationism, theism, deism, alien gods or whatever.

The point that can be made is that a code doesn't necessarily needs a creator, but unfortunately that point has to be done in just philosophical grounds as this particular instance isn't yet understood, and I don't recall of any other. I guess the argument would probably be something along the lines that physical complexity can increase from the basic assumption of fundamental physical laws, and theoretically it could eventually take the form some self-catalytic chain reaction, that could evolve further complexity by natural selection, and better "coding systems" would be selected.