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Sister, can you spare…?

Can you spare some hard cold cash for the possibility of a major genealogical breakthrough?

No guarantees, of course, and maybe we personally won’t live long enough to see it pay off.

But the more folks who join The Legal Genealogist and others in beating the drum for more mtDNA testing, the better our chances of making that breakthrough will be.

Here’s the deal.

DNA tests available today test three basic types of DNA for genealogical purposes:

Autosomal DNA tests — tests both men and women can take and the ones we’re taking when, for example, we test with AncestryDNA or MyHeritage DNA or 23andMe or in the Family Finder test from Family Tree DNA — look at the type of DNA we inherit equally from both parents and that helps us identify cousins to work with collaboratively on our genealogical research.1 These are by far the most popular DNA tests and the numbers of testers run into the millions — 20 million at AncestryDNA alone.2

YDNA tests — the ones only men can take — look at the DNA in the Y chromosome that only men inherit only from their fathers and that passes down the line from father to son to son largely unchanged over the generations. These tests then look at our father’s father’s father’s line.3 Family Tree DNA is by far the leader in these tests with its surname research projects and more than 775,000 testers overall, and the lowering price point for higher levels of testing has led to a growth in the popularity of these tests recently.

Mitochondrial DNA (mtDNA) tests — tests we all can take — look at the type of DNA we all inherit but only from our mothers, and so only women can pass it to the next generation. So these tests look at our mother’s mother’s mother’s line.4 The two big pools of mtDNA testers were those who tested with the National Geographic Society’s Genographic Project and those genealogists who’ve tested at Family Tree DNA. Between them, there are about a half million testers, and testing for genealogy is available at Family Tree DNA.

Now… database size matters. If you flip a coin twice and it comes up heads both times, you’re going to get the mistaken impression that heads = 100% and tails = 0%. Flip it 100 times, you’re much more likely to conclude that each is going to come up about half the time. It works the same way with DNA tests — the more tests we have to look at, the more we know about what it means when person A shares the same results with person B and the two of them are just that little bit different from person C.

And it’s that granularity — that level of detail — we need to really make use of these tests for genealogy. We need to know not just where we are on the human family tree, we need to know what main branch, what minor branch, what twig of the tree we’re on right now to what vein in what leaf. That’s essential for the guys with YDNA, and they’re well on their way with the Big Y testing.

But it’s not enough to figure that out just for the guys. We need to figure it out for us all with the mtDNA tree as well. And it’s even harder for mtDNA because it’s so stable — it changes so little from generation to generation. That means we need to extend and expand our understanding with even more tests so we can move from branch to twig to leaf to vein of the leaf.

And we get there by building the database size — the more tests, the more testers, the more data, and the higher the level of detail we get. Which means the more useful ultimately the data will be for genealogy.

Ten years or so ago, when there were just a few more than 8,200 full mitochondrial sequences tested (the highest level available), we could identify 3,550 mtDNA haplogroups — those twigs at the ends of the branches in our maternal family tree. That left a lot of people sitting out there on those twigs who were related, yes, but not all that closely.

By 2016, there were more than 24,000 full mtDNA sequence tests and 5,437 haplogroups could be identified. That may have gotten us to figure out what leaf on that twig we can call home, but still left us with a lot of folks too distantly related to be immediately useful for our research.

So the game plan is to get to a million full mtDNA sequence tests and rebuild the mitochondrial tree. The hope is that will get us a whole lot closer to the veins out at the edges of the leaves matching just those folks closely enough related that we might be able to identify our shared most recent common female ancestor.

It’s called the Million Mito Project, it’s being spearheaded by Family Tree DNA, and it will use samples from Family Tree DNA, the Genographic Project, and academic tests.5

And we can join in for that cold hard cash — the full not-on-sale price of a mitochondrial full sequence test at Family Tree DNA, the highest possible level of mtDNA testing and the level needed for this work is $159. That may sound like a lot since there aren’t any guarantees, especially now with everything we’ve been through in this pandemic. But maybe it’s just what we need to start looking forward from this pandemic. It’s the perfect reason to get together with that cousin we’ve been meaning to call to test that one grandparent who has the mtDNA we want to know about.

Want to know more? Check out this blog post by Roberta Estes, author of the DNAeXplained blog and one of the project’s research team.

Building the mtDNA database is citizen science at its best — it can greatly enhance the utility of mtDNA for future research.

Now I don’t mean to suggest for one minute that mtDNA testing isn’t valuable now to answer specific genealogical questions. Doing targeted testing of specific people to either rule in or rule out the women we think might be our ancestors is one of the most powerful tools available in genealogy. I’ve used it myself both to disprove one theory that a third great grandmother was Native American6 and to help prove which of a fourth great grandfather’s two wives was my fourth great grandmother.7

But we want to try to get to the point where we can use mtDNA for untargeted questions as well. To fish in the mtDNA pond for cousins to work with the way the guys can in the YDNA pond and the way we all can in the autosomal DNA pond.

Doing this testing without a specific target may not pay off with an answer to a genealogical question right now. It may not even pay off in our lifetimes. But building that database will pay off in the end.

My friend Diahan Southard says it best: untargeted mtDNA testing “is more or less a shot in the dark. But hey, if you don’t shoot, you will definitely miss!”8

And we will all miss out if we don’t take that shot.

So, sister, can you spare some cold hard cash to build a database? (NOTE: For clarity, yes brothers can also take this test! It will look at their — and our — mother’s mother’s mother’s line just as well!)

C’mon into the mtDNA testing pool.

The water’s getting better all the time.

Cite/link to this post: Judy G. Russell, “Building that mtDNA database,” The Legal Genealogist ( : posted 30 May 2021).


  1. See generally ISOGG Wiki (, “Autosomal DNA,” rev. 21 Oct 2020.
  2. See Leah Larkin, “AncestryDNA Surpasses 20 Million,” The DNA Geek, posted 27 May 2021 ( : accessed 30 May 2021).
  3. See ISOGG Wiki (, “Y chromosome DNA tests,” rev. 30 Oct 2020.
  4. See ISOGG Wiki (, “Mitochondrial DNA tests,” rev. 13 Feb 2021.
  5. See “What is The Million Mito Project?,” Family Tree DNA blog, posted 24 Mar 2021 ( : accessed 30 May 2021).
  6. See Judy G. Russell, “Oh, mama… a use for mtDNA,” The Legal Genealogist, posted 12 Feb 2012 ( : accessed 30 May 2021).
  7. See ibid., “Finding Margaret’s mother: the end,” The Legal Genealogist, posted 31 Jan 2021.
  8. Diahan Southard, “3 Reasons to Test mtDNA,” Your DNA Guide, posted 5 Jan 2019 ( : accessed 30 May 2021).
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