I am indebted to the wonderful Lost Cousins newsletter for a link to an article on the Genetic Genealogist website, which explains that it may be possible in the future to test artifacts such as licked envelopes and stamps, in order to test our ancestors’ DNA. As reported in this article on testing artifacts for DNA, genetic material was found on all samples in a test batch, which dated back to 1930.
I’ve often been told I ought to photograph and then throw away the original letters and other ephemera that I have in my family history archive, but maybe I should hold on to it for a bit longer. Bear in mind that your DNA generally only includes material from about 120 individuals, and you have twice as many ancestors as your parents, and four times as many as your grandparents. So the likelihood that your grandparents’ DNA may identify individuals who don’t show up in your own DNA sample is quite high.
So keep those letters and postcards! You never know when the technology may become sensitive enough and cheap enough to make testing great-grandmamma’s DNA from a stamp licked a century ago a real possibility.