Before the printing press allowed exact copies of texts, such as Bibles and other works, scribes would copy manuscripts by hand. These copies were imperfect and these mistakes would then be replicated as other scribes made further copies. The implication is that the church was practicing evolution before science had even discovered it. Darwin could've just popped down to his local monastery or church instead of cruising around the world.
Scientists have used phylogentic software to look at these texts in order to discovery the original document sources (creating a book of life if you will). Like evolution in the natural world, the mutations aren't random and you get errors such as recombination, lateral transfer, deletions, and even convergent evolution. There are some interesting relationships that can be determined, such as certain areas of text are more likely to have mistakes in them than others.
What's cool about a theory, such as evolution, is that it can be applied to many different areas such as natural languages, behavioural patterns, archaeological artifacts, and written works such as chain letters and medieval manuscripts.
More information, Manuscript evolution and Phylogenetics of artificial manuscripts.