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Ancestry

Hello, I did an African mtDNA ancestry test in hopes of pinpointing a tribe of my African lineage (that's what the company claimed they do). I'm an African-American woman. I received my results and it said that my lineage was of European descent, non-African. What does this mean? I was very confused because I'm clearly black as are my parents and grandparents before them.  Does that mean there is no African in me at all or that they just didn't find it? 

-A curious adult from Florida

April 3, 2013

There is undoubtedly plenty of African in your DNA.  The problem is that the mitochondrial DNA (mtDNA) test missed it.  Which isn’t surprising if we dig a little deeper into what this sort of test can actually tell you.

A mtDNA test can look deep into the past which is why it is so useful for the kind of information you were looking for.  But its big disadvantage is that it can only follow your maternal line back.  And in fact, it can really only trace back a single maternal line.

Mitochondrial DNA is passed from mother to children.  So you get your mtDNA from your mom, who got it from her mom and so on all the way back to Mitochondrial Eve

This obviously means that the test ignores your dad’s side of the family since you do not have his mtDNA.  But it also means that it is ignores your mom’s dad’s mtDNA because your mom only got hers from her mom.  

And it ignores lots of other relatives from your mother's side of the family too.  Pretty much anyone not on a direct maternal line will be missed.

It also means that it takes just a single ancestor from a different ethnic group to move the line onto a whole new track.  Imagine that ten or fifteen generations back, one of your ancestors along the maternal line was Caucasian.  Now as we trace the line back, we are tracing her line back.  You would look Caucasian. 

This would be true even if everyone after that woman had kids with African Americans.  There wouldn’t be any dilution of the mtDNA for the 200-300 years.

And in reality, we don’t need to go back ten or fifteen generations.  Imagine a man like President Obama took one of these tests.  His results would come back as 100% white, no black whatsoever because his mom is Caucasian.  This is even though he is obviously half black from his dad.

Something like this almost certainly happened to you.  There is probably an unbroken line back to a Caucasian woman and so your mtDNA looks Caucasian.

This kind of result is always a risk with mtDNA tests.  They are incredibly powerful and incredibly limited at the same time.  They can tell you a lot about distant relatives but you can only see a small subset of them.

DNA tests that look at the rest of your DNA, autosomal DNA tests, are also incredibly powerful and incredibly limited at the same time.  While they let you look at all of your direct relatives, they can only go back a few generations.

So autosomal DNA tests would definitely find African in your DNA but they wouldn’t be able to see very far back in time because of how DNA is passed down.  In fact these DNA tests can only go back reliably four or five generations. 

What this means is that an autosomal DNA test would immediately have found that you were African but it probably would not have been able to tell you the tribe(s) your ancestors came from.  And it would have missed your white ancestor too!

All of this points to the importance of not just getting one kind of test.  If you are male, get a Y chromosome, a mtDNA and an autosomal DNA test. If you’re female, get the mtDNA and the autosomal test and if you can, have your brother or father have his Y chromosome done.  Then you’ll get a much more complete answer about your ancestry.

Of course that is easy to say but these things are not cheap!  But to get a complete answer, you do need to do them all.  And even then, you might not find out exactly what you are looking for.  Or even the “right” answer.

Half an Answer

As I said, most of our DNA gets diluted over the generations.  We share 50% of our DNA with our parents, 25% with our grandparents and so on.  Once you get to about 1%, the relationship gets very hard to see with current DNA tests.

This is not the case with the Y chromosome or the mtDNA.  The Y is passed from fathers to sons, virtually unchanged, generation after generation.  And mtDNA is passed from mothers to children in the same way.

Let’s look in more detail at a case where someone would be over 99.9% African American but look white in a mtDNA test.  Imagine it is 1813 and a child is born of a white mother and a black father.  We will draw this out like so:

In this diagram, men are squares and women are circles.  Also, Caucasians are shown in white and African Americans in black.

On the left, we will follow the mtDNA.  As you can see, mom passed hers on to her daughter and so both are represented with white circles.

On the right we will follow the rest of the DNA (the autosomal DNA).  Here the daughter has half her DNA from mom and half from dad.  I am showing this with a half white and half black circle.

Now let’s say the daughter marries a black man and they have a daughter.  Here is what that would look like:

It is lined up the same way.  Notice that on the mitochondrial side, she is still 100% white but is only 25% white on the autosomal side.  Let’s keep going for a five or six generations (sorry my PowerPoint skills are a little rough):

As you can see, on the left the great, great, great granddaughter still looks white with a mtDNA test.  But on the right, you can barely see it anymore. 

It is now 1913 and we are getting close to your situation.  Some people alive today will remember the woman from 1913 and all the subsequent kids and they will all be remembered as black.  This is even though back in 1813, their direct maternal link was white.  

Something along these lines is probably what happened in your situation.  We don’t know how far back it was but your mtDNA most likely looks Caucasian because of a woman from long ago. 

This of course does not mean you aren’t African.  A look at the family tree on the right clearly shows lots of African heritage.  Heck, even the first image from back in 1813 showed half African heritage!

So buyer beware.  DNA ancestry tests can be very useful if you know going in what their limitations are.  But don’t over interpret them…take any results with a grain of salt.

Even if you don’t find what you expected, that can be cool too.  Your mtDNA test let you know about a long lost ancestor that you may not have known about at all.  Perhaps a story of forbidden love from hundreds of years ago… 

By Dr. Barry Starr, Stanford University


President Obama would be 100% Caucasian in a mtDNA test.

 

 

 

 

 

 

 

 


You can only follow most of your DNA back four or five generations.


The DNA found in mitochondria like this one does not become diluted over the generations.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


There is a Caucasian woman in a direct maternal line somewhere in your family tree.