Recently, someone’s mitochondrial DNA test revealed that their ancestor was from Africa, but that person had no African heritage showing in their autosomal results or revealed in their genealogy.
They wondered how this was possible and which test was “wrong.” The answer is that neither test is wrong.
Mitochondrial DNA is important EXACTLY for this reason. It does not divide with inheritance, while autosomal DNA does and eventually disappears entirely.
Mitochondrial DNA is inherited from our direct matrilineal line – our mother – her mother – on up the tree directly through all mothers.
If you need a refresher, the article, 4 Kinds of DNA for Genetic Genealogy shows how different types of DNA are inherited from our ancestors.
Mitochondrial DNA and Ethnicity
Let’s look specifically at mitochondrial DNA ethnicity as compared to autosomal ethnicity.
In the chart above, an African ancestor (or ancestor of any ethnicity) who was the only ancestor of that ethnicity in your heritage is shown at the top – your five times great-grandmother. Using a 25-year generation, their autosomal DNA would have been admixed with partners of a different ethnicity 7 times between them and you.
Of course, that means the autosomal DNA of that ancestor would have been divided in (roughly) half 7 times.
Percent of Inherited Autosomal DNA
In the Percent of Inherited Autosomal DNA column, we look at it from your perspective. In other words, of the 100% of your ethnicity, stepping back each generation we can see how much of that particular ancestor you would carry. You carry 50% of your mother, 25% of your grandmother, and so forth.
You inherited approximately 0.78% of your GGGGG-Grandmother’s autosomal DNA, less than 1%.
If she was 100% African, then that 0.78% would be the only African autosomal DNA of hers that you carry, on average. You could carry a little less or a little more. We know that you don’t actually inherit exactly half of each of your ancestors’ DNA from your parents, nor they from their parents, so we can only use averages in that calculation.
Ancestral Percent Autosomal Ethnicity
In the Ancestral Percent Autosomal Ethnicity column, we look at it from the ancestor’s perspective.
Of your GGGGG-Grandmother’s 100% African ethnicity, how much would each subsequent generation be expected to inherit of that ethnicity, on average?
You would inherit 0.78% of that ancestor’s DNA. Given that GGGGG-Grandma was 100% African in this example, you would carry 0.78% African ethnicity.
Percent Mitochondrial DNA Inherited
Now, look at the Percent of Mitochondrial DNA Inherited column. Your African GGGGG-Grandmother’s mitochondrial DNA was 100% African in her generation, 7 generations ago, and still is 100% African in you, today.
That’s the beauty of mitochondrial DNA. It’s a forever record – never divided and never washes away.
How else would you EVER figure out her African roots today without records? Even if you did inherit a small amount of autosomal African DNA, and the vendor reported less than 1%, how would you determine which ancestor that African DNA came from, or when?
Not to mention trying to figure out if less than 1% or any small amount of reported ethnicity is a legitimate finding or “noise.”
What about if you, like my friend, carried no African autosomal DNA from that ancestor? There would be nothing to report in your autosomal ethnicity results – but your mitochondrial DNA would still tell the story of your African ancestor. Even after that trace is long gone in autosomal DNA.
Mitochondrial DNA is MUCH more reliable for each specific line in determining the “ethnicity” or biogeographical ancestry of each ancestor. I wrote about how to use your mitochondrial DNA haplogroup, here.
Discovering Your Forever Record
Everyone can test for their own mitochondrial DNA, and you can test other family members for their matrilineal lines as well. For example, your father or his siblings carry the mitochondrial DNA of his mother. You get the idea.
I record the mitochondrial haplogroup of each of my lines in my genealogy records and on their WikiTree profile card so others can share – now and in the future.
Genealogy research of female ancestors is less difficult with at least “one” record that reaches back where surnames and autosomal DNA don’t and can’t.
What will your mitochondrial “forever history” reveal?
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