One of the most common questions I receive about mitochondrial DNA is what matches with 1 or 2 differences, meaning mutations, mean relative to how long ago the two people are related.
And the answer, is, of course, “it depends.” Don’t you just hate that.
First, it depends on whether you are referring to just the mutations in the HVR1 or HVR1+HVR2 regions, or the entire full sequence. Clearly, the full sequence test provides the most refinement, because it tests the entire mitochondria, all 16569 locations, and compares them with others who take the full sequence test.
Family Tree DNA has this to say.
- Matching on HVR1 means that you have a 50% chance of sharing a common maternal ancestor within the last fifty-two generations. That is about 1,300 years.
- Matching on HVR1 and HVR2 means that you have a 50% chance of sharing a common maternal ancestor within the last twenty-eight generations. That is about 700 years.
- Matching exactly on the Mitochondrial DNA Full Sequence test brings your matches into more recent times. It means that you have a 50% chance of sharing a common maternal ancestor within the last 5 generations. That is about 125 years.
Because of the constantly changing surnames of the females as they marry, it’s very difficult to track the mitochondrial line back very many generations.
Recently, a paper was published, titled “Identification of the remains of King Richard III” by Turi King et al, that focused on identifying the skeletal remains found in 2012 in Leicester as those of King Richard III. Interestingly enough, one of the ways that they confirmed the identity of the remains is through mitochondrial DNA matching.
In order to do this, the researchers had to find at least one individual who descended directly from a matrilineal line in common with Richard. The mitochondrial DNA is passed from the mother to all of her offspring, but only females pass it on. Richard’s sister, Anne of York, had two descendants who fit the bill, and both of them were willing to DNA test.
The results compared the full mitochondrial sequence, and it was determined that in one case, Richard and the participant were an exact match, and in the second case, only one mutation difference.
This is really quite interesting because we can see a real life example of mutations that do, and don’t occur. In this case, the timeframe involved was over 500, almost 600, years since the births of Richard and Anne from their common ancestor, their mother, Cecily Neville.
As this chart of descent from the supplementary materials from the paper shows, there were 18 generations in the case of Michael and 20 generations in the case of Wendy. We know that there was no mutation in this line from Anne of York through Catherine Manners, because Catherine would have passed any mutation she carried to both of her children, so the one single mutation in one of the descendants’ results happened someplace between Catherine and the present day testers.
So while you may have a common ancestor with someone you match exactly at the full sequence level in the last few generations, you may also share an ancestor a long way back on your common tree – much further back than most of us will ever be able to reach genealogically – unless, of course, you’re lucky enough to be descended from King Richard III’s mother.