A flock of sheep, goats and cattle: ancient DNA analysis reveals complexities of historical parchment manufacture

Parchments comprise one of the most common and valuable sources of archaeological and historical data. Previous studies have shown that parchment also preserves genetic data. These data could be valuable for population studies, to understand past animal husbandry, the development of breeds and varieties and to comment on the provenance of parchments. To improve our understanding of DNA contained in parchments, we analysed genetic data, including both mitochondrial and autosomal loci, from 18th to 19th century English parchments which stable isotope analysis had indicated were well-preserved. DNA results were unexpected. All but one of the parchments produced multiple sequences matching several different species. Ion beam analysis ruled out surface treatments of the parchments (including ink and animal glues) as the origin of these multiple sequences. Our results suggest that the DNA content of parchment is more complex than previous research has suggested and that multiple stages of parchment manufacture, treatment and storage are preserved in parchment DNA extracts.