I'm writing a story which is intended to be mostly realistic and historically accurate, but with one character who is biologically immortal. She is born in a Pictish/Caeldonian/Celtic village in modern-day Scotland, and by the time the story begins, she lives in a small town in the Pacific Northwest of the United States. The town is more or less run by a secret cult which worships her and helps protect her secret from the outside world.

My question is centered around a character who is part of this cult. While fleshing him out, I had the idea that he could be a direct descendant of the immortal character. While doing research, I learned that Celtic (not sure about Pictish or Caeldonian) society was somewhat matriarchal, and genealogy was "recorded" (though not in writing in this context) along the matrilineal line. This made me think the descendant character could be from a direct matrilineal line, and when I looked into DNA testing, I found a source saying that mtDNA testing is useful for following the matrilineal line specifically.

I'm now trying to come up with a plausible scenario that explains how the cult tracked down the descendant character. The story takes place in 1987, and the cult needs to have found the descendant character by then. I found a source saying that mtDNA was available during the 1980s, but also various sources saying that commercial DNA testing was not widely available until later. I also found a source which, based on my reading, says that mtDNA testing is most effective as a way of proving or disproving an existing hypothesis about matrilineal descent.

In my ideal case, the cult has information along these lines:

  • Reliable information about the immortal character's descendants for the first 200 years of her life, based on her memory
  • Some gaps following this
  • Some hypotheses about possible descendants from 300-600 AD (along with reliable records for each candidate's descent)
  • Some gaps
  • More hypotheses/reliable information (in isolation), etc.

mtDNA testing would then ideally let them fill in these gaps in a way that would require a bit of luck, as well as a lot of work to collect DNA samples, but not be completely implausible.

(Edit to pose only a single primary question)

Based on all of this context, I particularly want to know: would mtDNA testing make it easier to establish ancestry between the immortal character and a direct matrilineal living descendant of hers, assuming that the cult is already aware of him or her as a potential candidate based on known records?

  • $\begingroup$ A concern with the what you have posted is multiple questions.. There should be one question being asked. I grant you the most of them are highly related. But it will likely attract close votes. I would say restructure to highlight your primary question (which should match the title) and have the others as being refinements narrowing down your question, $\endgroup$ Oct 7, 2023 at 0:50
  • $\begingroup$ "To establish ancestry" = "to establish the existence/presence of ancestry"? Secondly: now that you seem to have settled on a question, I'm not sure how much the rest of the question matters. Moreover, if your question is simply if mtDNA testing can prove ancestry between two (potentially matrilineally related) individuals, then this might not even be the optimal Stack Exchange site for that. $\endgroup$
    – Joachim
    Oct 7, 2023 at 19:33
  • $\begingroup$ In 1980's, they did not have DNA databanks (or if someone did have, the number of samples was way too low to track anyone). Also, just taking samples and analyzing them was not an option: back then doing so would have been too slow, and potentially too expensive as well. Tracking would have needed to be done using other means (traditional detective work), and mtDNA would be of any use only when suitable candidates were found. And, even then it would be a bit unclear what their actual relationship was (see the second item in AlexP's answer). $\endgroup$ Oct 8, 2023 at 0:29

3 Answers 3

  1. In the 1980s only some scientific laboratories had the capability to compare mitochondrial DNA. The technology became more commonplace in the 1990s. But, yes, there were sufficiently many laboratories in universities and research institutes in the 1980s which could have done the comparison. For example, the MRC Laboratory of Molecular Biology in Cambridge, England.

  2. But comparing mitochondrial DNA cannot prove that the wannabe prince is a descendant of the ancient queen. He could be a descendant of one of her sisters. Or he could be a descendant of one of her maternal aunts. Or he could be a descendant of one of the sisters of her great-great-great-great-grandmother.

  3. Because the wannabe prince having the same mitochondrial DNA as the ancient queen only proves that they are descended from a common female ancestor in female-upon-female line. Yes, they are related; but how closely related remains unknown.


With Cheddar Man they were able to find a descendent of a 9000 year old skeleton living half a mile away. The qualifications of AlexP's answer still apply.

It would be interesting to speculate whether an immortal had static DNA. Different branches of a Bristlecone pine may have had a common ancestor 5000 years ago, but can be very different. Wood-boring beetles can have many generations in a summer, and the tree has to keep resistant somehow. This is why most of the branches on an old one will be dead.


Two factors can combine to make this practical:

Does the immortal have unique, or extremely unusual, mitochondrial DNA? If so, it is more of a distinguishing feature for her descendants. If her mtDNA is unique, perhaps because it's part of the reason for her immortality, it's an identifying feature.

When did the immortal stop having children? There's no obvious reason she should go through menopause at the usual kind of age. If she has had children relatively recently, say in the early 20th century, it's possible to trace her descendants through ordinary means, and the mtDNA test is only needed for confirmation.


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