If you have checked your Y-DNA or mtDNA matches on Family Tree DNA, then you have noticed that they are organized by genetic distance. In this post, you will learn what genetic distance is on FTDNA, as well as:
- The difference between genetic distance in Y-DNA and mtDNA
- How to use genetic distance to calculate how far back your common ancestor might be
Most people understand that mtDNA and Y-DNA test results have limited use in genealogy. Even so, understanding the concept of genetic distance can help us take advantage of ways which the results can be helpful to us.
All of our Y-DNA and mtDNA matches are related to us. We share either a direct-line paternal or maternal ancestor with them.
If you are female and are administering the test results of your father or brother, the Y-DNA matches are related to you, too.
Even though we are related to all of those matches, our common ancestor could have lived many thousands of years ago. No one has a reliable family tree that goes back that far, and so it’s basically impossible to identify who the common ancestor might have been.
This is where genetic distance can help us out.
What does genetic distance mean?
When DNA testing companies test our Y-DNA and mtDNA, they test a specific number of locations in our DNA in order to identify the mtDNA or Y-DNA haplogroup to which we belong.
In order to provide us with a list of our mtDNA and Y-DNA matches, they identify other customers who have also had their Y-DNA or mtDNA tested in order to provide us with our DNA matches.
Since mtDNA and Y-DNA mutate slowly over the course of many generations, people who match at more tested locations (markers) than others match at a closer genetic distance. This means that the common direct-line paternal or maternal ancestor is not as far back in time as matches who don’t have as many identical locations.
Some of the more thorough tests, which also happen to be more expensive, test most or all of the locations in the mtDNA and Y-DNA and can provide more accurate matches.
How to understand genetic distance in mtDNA matches
The meaning of the genetic distance on your mtDNA match list will depend on the type of mtDNA test that you took. Currently, the only mtDNA test available on FTDNA is the mtFull Sequence test.
For those that took the mtFULL Sequence test, the guidelines below can help you understand how to interpret the genetic distance of your matches:
- EXACT match (genetic distance of 0) = 50% odds of the most recent direct-line maternal ancestor being within the past 5 generations
- More distant genetic distance = the odds increase dramatically that you are very distantly related
Some people may have taken the mtDNA HVR1 one test. mtDNA matches on this match list are at a 50% confidence level that the most recent direct-line maternal ancestor is closer than 1,300 years ago (or 52 generations!) at the closest genetic distance.
In other words, the match may or may not be more closely related than a direct-line maternal ancestor who lived in the year 719.
Matches for this test at further genetic distance levels can be VERY far back in time, essentially impossible to trace with genealogy.
How to understand genetic distance for Y-DNA matches
Genetic distance for Y-DNA matches on Family Tree DNA will depend on the type of test that you decided to take. If you took the “Y-111” test, then the following guidelines might apply:
- Genetic distance of 0 = almost certain that there are less than 6 generations to common direct-line male ancestor
- Genetic distance of 1 = almost certain that there are less than 9 generations to common direct-line male ancestor
- Genetic distance of 2 = almost certain that there are less than 11 generations to common direct-line male ancestor
If you took the Y-DNA-37 test, which is less detailed, the genetic distance is slightly less certain:
- Genetic distance of 0 = probably related within the past 8 generations
- Genetic distance of 1-2 = definitely related within the past 500 years
- Genetic distance of 3 = probably related within the past 500 years
As you can see, only both test types, there is a big difference in how many generations you would have to go back in one’s family tree to find the common direct-line male ancestor.
Will you share autosomal DNA with Y-DNA and mtDNA matches?
It’s unlikely that you will share autosomal DNA with your Y-DNA or mtDNA matches unless they are known relatives and are relatively closely related to you and are EXACT matches to your highly detailed Y-DNA or mtDNA results. The reason for this is due to the inheritance patterns of these different types of DNA.
It’s also important to remember that most of our Y-DNA and mtDNA matches might be related to us 1,000 years or more back in time.
Y-DNA and mtDNA can be passed down with very few changes for dozens of generations. We inherit only 50% of our parents’ autosomal DNA, however, which means that over the course of a dozen generations or more, distant cousins descended from the same ancestor likely won’t share measurable autosmal DNA.
With that said, we do share autosomal DNA with all of our close family and many of our distant relatives, so if you believe that one of your mtDNA or Y-DNA matches is more closely related than, say, 4th cousin or so, it’s probably worthwhile to do an autosomal DNA test to see if you match.
How to get your Y-DNA and mtDNA test
If you haven’t yet tested your mtDNA (everyone) and Y-DNA (males only), I highly recommend doing so. mtDNA and Y-DNA results can help you find more relatives and provide additional evidence to support your family tree. You can also use mtDNA and Y-DNA information to disprove relationships.
There is only one company that is recommended for testing mtDNA and Y-DNA, and the name of this company is Family Tree DNA.
I hope that this post has helped you understand more about what genetic distance means on Family Tree DNA, as well as how it can help you with your genealogy pursuits. If you have any questions about something that you read in this post, I would love to hear from you in the discussion below.
Thanks for stopping by today!