Yesterday I posted a brief challenge to Creationists: define what you mean when you say that no known mechanism can add information to the genome. Nobody has accommodated me by taking up the challenge, so I’ll just get straight to the interesting part. (I know I didn’t allow much time, but I’m bored and have several hours to waste use productively until my next lecture.)
The information ‘problem’ is a relatively recent Creationist claim, and is a good indicator of the trend away from easily-debunked myths about the fossil record or radiometric dating and towards more complex (to them) myths about the genome or cellular biology. You’ve probably heard it a dozen times before: “Information can’t be added to the genome”. But what does this actually mean? There are a seemingly endless number of variations based on what ‘information’ and ‘genome’ are defined as (Creationists seem peculiarly unable to agree on basic terminology), so I’ll just go through the most common ones and debunk them all.
1) Genetic material cannot be added to the genome. This one often shows up when a Creationist is pressed to define what they mean by ‘information’, what which point they fall back on the simplest definiton Wikipedia can think of: actual DNA base-pairs. The ‘letters’ of the DNA ‘language’ (as I’m sure no Creationists reading this need to be told!) are A, G, C and T, which stand for Adenine, Guanine, Cytosine and Thymin respectively. RNA, DNA’s more simplistic cousin, replaces thymine with U, or Uracil. Each letter has a complimentary letter on the other side of the famous ‘double helix’ – A with T and G with C. They can only form hydrogen bonds in this way; you cannot, for example, have A joined to C. These are ‘base pairs’, and they are directly analagous to the 1s and 0s of computer binary information.
Enough of the elementary biology: does this version of the information argument carry any weight? It does not: gene duplication (and in some particularly dramatic examples, whole genome duplication) is a process that commonly adds large amounts of genetic material to the genome. There are others as well, but you get the idea.
(b) Gene duplication just copies the same information again, rather than adding new information. This sub-myth stops making sense when you apply a little though to it; if a duplication increases the amount of raw genetic data in the genome, subsequent mutations of that new data will lead to an increase in both new information and more varied information. As we’ll see in a minute, though, this isn’t even necessary.
2) Mutations don’t add information, they destroy it. This one is a bit of a word game, because it plays on the fact that mutations are ‘mistakes’ in the genetic copying process. It is never clear what Creationists mean when they say that mutations ‘destroy information’ – presumably they don’t mean that the actual DNA base pairs always disappear, so they must be working off some other definition of ‘information’. As far as I can work out, they’re usually talking about the phenotype rather than the genotype, and falling back on the Creationist myth that mutations are always harmful. Of course, this is not the case – benifical mutations, while quite rare, have been found to occur with enough frequency to allow natural selection to take place.
(b) A mutation only adds information if it conveys a benefit to the organism. Again, this sub-myth is tied to the idea that mutations are always harmful. It’s also a brilliant example of the ‘moving goalpost’.
3) Mutations don’t add information. This one is even more vague, but it’s by far the most common version of the myth (even if the word ‘mutation’ isn’t actually used). Here, most Creationists are unknowingly invoking Information Theory (or Shannon-Weaver Information Theory), a field of mathematics that can be applied to many different situations. According to this theory, the ‘random noise’ of mutation actually helps to increase genetic information. Any reduction in redundancy (genetic material that does nothing, of which there is an enormous amount) is an increase in information. This is why I said earlier that duplication is not necessary for an increase in information: because the genome of any organism is huge, there is ample room for mutation to create new genes.
(b) There is no ‘junk’ DNA. This sub-myth attemps to negate the above defence by claiming that there is no ‘junk’ DNA, and that any mutation of existing genetic material will most likely lead to a negative effect on the organism (it is true that harmful mutations are more common than beneficial ones). Since genetic information supposedly cannot be added to the genome (as per Myth #1), the genome must be a more-or-less static entity, with only minimal variation allowed. It’s wrong, obviously: while some non-coding DNA does seem to have a purpose, very large sections of an organism’s genome can be cut out or reversed without any noticeable effect on the organism. (Incidentally, the idea of the genome as static and mostly unchanging is very appealing to those who believe in the special creation of the Bible or Qur’an. This type of thing is a good red flag to look out for when someone claims to reject evolution on purely scientific grounds; the religious bias is always lurking somewhere in the background.)
(c) Mutations just corrupt the genetic template. Vaguness-ahoy! This one plays off of the idea that there’s an original or ‘ideal’ form of the genome, and that any variation on this is corruption (and as we all know, corruption is a bad thing). Usually there are some appeals made to Adam as having this mytsterious ideal genome – if someone goes this far into the waters of fundie-hood, you can safely begin to ignore them. In reality, there is no such thing as an ‘ideal’ genome, for any organism. (The Human Genome Project took examples of those sections of the human genome which vary from many different individuals, since taking it from any one individual would have lead to a database that didn’t represent the diversity of humanity. Too bad they didn’t have any of Adam’s cells lying around!)
(c) Richard Dawkins couldn’t give an example of a process that adds information to the genome. This one is pretty irrelevant, but I thought I’d toss it in here anyway since it’s so common. According to Dawkins, he invited a camera crew into his home to give an interview on what he thought was to be a documentary on the interaction between science and religion. When he was asked about genetic information (with the question phrased in a way that made it sound as if it was lifted directly from Creationist literature) he realised what was happening and, in accordance with his rule about not debating Creationists, decided to cut the interview short there and then. While the cameras were off, the film crew supposedly begged him to continue (they had come a long way) and he relented. when the documentary was aired, he was appalled but not surprised to discover that it had been edited in such a way as to make his long pause (when he says he was deliberating over whether to answer) look like an inability to come up with a reply, followed by a quote, taken out of context, that made him seem as if he was trying to dodge the question.
Obviously only those involved know for sure what actually happened, and the possibility that Dawkins is lying can’t be ruled out. However, I find it hard to believe that he would be unable to answer a question like this, and Creationist deceit is not exactly unprecedented – the widespread use by them of ‘quote mining’ throughout the internet is evidence of that, as is the dubious methodology employed by the producers of Expelled. But, as I said earlier, whether Dawkins was able to answer the question or not is irrelevant, since the scientific evidence clearly and easily refutes this particular Creationist myth.
As usual, comment, criticism and suggestions are very welcome, particularly from those who know more about this than I do and feel that I missed something important due to ignorance of the subject, or that I made a mistake.