from Scientific American -
How Old Is That Book? DNA May Hold the Answer
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An interesting approach to dating unknown samples by cross-referencing with DNA signatures on parchment manuscripts with known dates. However, the practice of "recycling" earlier manuscripts for later use - by scrapping down and cutting manuscripts - would present problems in terms of dating the *later* creation.

See also earlier posts on other dating techniques for paper-related artefacts.
"Water pores reveal age of paper"
"Print Clock: A method for dating early books and prints"
"'Print Clock' Dates Antique Books"
.