It's clear what a mutation is in genetics: a strand of DNA gets hit by a cosmic ray, or copied incorrectly, and some error gets introduced into the sequence. For example, an 'A' gets turned into a 'G', although they can be much larger in effect. These errors can range from causing no problem whatsoever (don't worry - the majority are like this), to causing large-scale issues due to the change in a single letter of DNA, such as in the case of sickle-cell anemia.

Well, there are also systematic errors in copying a text. Whether it's skipping a word or duplicating it, there is order to the ways in which a scribe's mind wanders during his transcription. Many of the errors can be grouped into categories of error, just like the different types of genetic mutations. And not only are there regularities to how both DNA and ancient manuscripts are copied, but it gets even better: despite the differences in terms, these types of errors are often identical.

For example, there is a scribal error known by the Greek term homeoteleuton. This refers to a type of deletion, where there are two similarly ending passages and the scribe skips to the second ending without transcribing the first intervening portion. For example, if a section read, "And you should do the following things because I am the Lord. Here's what you should do, because I am the Lord. Amen." and it was instead copied as "And you should do the following things because I am the Lord. Amen." that would be a homeoteleuton.

Well, in genetics this error is simply known as a mutation called slipped-strand mispairing. AATTCGATATACGA gets copied as AATTCGA. Smaller slipped-strand mispairs also exist, and are known in paleography as haplography, where such a miscopy and deletion occurs within a single word (like going from metoposcopy to metoscopy, both quite rare words).

Insertions can occur during copying in both genetics and paleography as well. This is called dittography for manuscripts, and, well, insertions, in genetics. There are also reversals: metathesis in paleography and chromosomal transpositions in genetics. And point mutations, substituting the wrong genetic base when copying DNA, also occur in handwritten manuscripts. In both cases, the wrong letter is written, based on probabilities of being similar. In DNA, A and T are quite similar chemically and can be confused easily. In ancient Greek, lambda and delta look similar and are more likely to be exchanged as well. And the list goes on.

While fun to chronicle such similarities, these similarities can also be exploited in the same way. Mutational differences between DNA sequences can be used to understand the evolutionary history of a population, or even a group of species. And so too with variants of the same manuscript. A famous example of this is from a 1998 research article in the journal Nature that quantitatively studied the differences between the 80 surviving versions of Geoffrey Chaucer's The Canterbury Tales. By subjecting the variants to a battery of genetic analyses, the researchers were able to better understand the contents of the ancestral version, Chaucer's own copy!