How Random is Random Mutation on DNA?

"If we want to postulate a deity capable of engineering all the organized complexity in the world, either instantaneously or by guiding evolution, that deity must have been vastly complex in the first place.

The creationist, whether a naive Bible-thumper or an educated bishop, simply postulates an already existing being of prodigious intelligence and complexity."
Richard Dawkins


This post forms part of a series on Mr Marshall's Random Mutator. You can find all the posts here:

1. The Random Mutator of Perry Marshall.


2. Is DNA Analogous to Human Language?


3. How Random is Random Mutation in DNA?


4. Does Darwinian Evolution Claim that DNA Mutations are Random?

What is mutation?

Simply put, a mutation is a change in the nucleotide sequence of the genetic material of an organism. This genetic mutation could cause changes in the phenotype of your species. For example, you could have a mommy and a daddy with blue eyes who give birth to a child with brown eyes.

What causes mutation?

"Mutations can be caused by copying errors in the genetic material during cell division, by exposure to ultraviolet or ionizing radiation, chemical mutagens, or viruses, or can be induced by the organism, itself, by cellular processes such as hypermutation."
[Mutation, Wikipedia]

Copying errors, you say? One would think that a system intelligently designed by an omniscient, omnipotent deity would not be prone to copying errors. It surely wouldn't be sensitive to ultraviolet radiation either, given that an omniscient deity would've seen that one coming.

Similarly, if mutations were not random, but predicted and designed by a perfect designer, one would expect that these errors would not be copied over to the next generations, but that some error-correcting mechanism would be in place. This would ensure that if you exercised your free will too leniently and you ended up next to a UV light for too long that your children and your children's children are at least protected from your inability to practice sound discrimination towards malignant types of light sources.

Do mutations in DNA occur randomly and indiscriminately?

This is exactly what Mr Marshall's random mutator suggests. However, in DNA, you don't have one string, like you do in Mr Marshall's random mutator. You have two strands. Both strands consist entirely of the letters A, C, G and T. An A on the one string mostly (but not necessarily) corresponds to a T on the other strand, and vice versa. A C on one strand mostly (but not necessarily) corresponds to a G on the other strand, and vice versa. More significantly, any possible combination of A, C, G and T is a proverbial word in the language of DNA.

This is important, because not all combinations of letters in Plain English are words. Mr Marshall would do well to model his random mutator so that it bewares of the Jabberwocky. At least this would resemble the working of one strand of DNA somewhat. Since any combination of letters in the DNA alphabet form meaningful words in the genetic code, there is no possibility that a random mutation would prevent your genetic information from being transferred. It follows that the randomness of mutation in DNA is immaterial, because no mutation would cause your organism to necessarily become extinct.


A Cro-magnon skull. Mr Marshall's random mutator reasons that natural selection implies that we can revert our current human population back to Cro-magnons, and if we can't evolve to our current level of humanity, humanity would necessarily become extinct.

Mutation does occur randomly, but not indiscriminately thanks to natural selection. A mutation in some of your DNA is not necessarily a mutation in all of your DNA, or in all of the DNA of a particular species, as only the mutations which get passed on to your offspring are relevant. Mr Marshall's mutator does not model this scenario at all, but his model implies that any random mutation in the DNA of a particular organism automatically occurs species wide.

Mr Marshall's random mutator does not model natural selection

Mr Marshall reasons that since you can mutate randomly and then revert back to your selected text, his mutator does model natural selection. I fail to see how taking modern day humans and reverting us back to archaic homo sapiens has anything to do with natural selection. Besides, his 'Revert To Selected Text' button does not in fact revert back to selected text. It entirely clears the text. As an information scientist, Mr Marshall should surely be aware of Nielsen's heuristics. Poor user interface design does nothing to bring your point across more clearly.

Natural selection is not a carefully designed, directed process. Nor is it capable of being completely ignored in a model of mutation. Sticking with Darwin's definition:

"One general law, leading to the advancement of all organic beings, namely, multiply, vary, let the strongest live and the weakest die".
[Wikiquote, Charles Darwin]

There is nothing in this mutator that models selecting the strongest letters, words or sentences, and letting the weakest letters, words or sentences die. Note that this mechanism does not imply a designer. This mechanism could be brought about by an outbreak of Aids in your population.

Surely, if your DNA were designed by a perfect, omniscient deity, she would've seen that one coming too? Why then are some people immune to Aids while others are not? Why then are some more immune to malaria, while others are not? Natural selection seems to explain that, without the need for a designer. Mr Marshall's random mutator does not.

By the way, I haven't mentioned Cthulhu in this post. I just thought I'd randomly mention that.