How Far Back is an Ancestor Based on Ethnicity Estimates?
When you look at your genetic ethnicity estimates, have you ever wondered just how far back you have to look on your family tree to determine which ancestor has that heritage?
Was This You?
Did you take a DNA test was to learn your heritage? When you received your results, did you see your ethnicity results and find some curious percentages?
Maybe you're mostly European. Maybe you're mostly African. Maybe you're mostly Asian. But in many cases, you might see that, hey, there's one or two percent that is something you weren't expecting.
Perhaps you want to know whether or not some of these small percentages could actually be identified with an ancestor sometime in the past.
Understand Genetic Inheritance
Sadly, your ethnicity results probably don't have a lot to do with genetic genealogy. However, to begin answering where your 1% ethnicity comes from, you first need to understand genetic inheritance. The following chart will help.
On average, we know that we get 50% of our DNA from our parents. This halves again each generation going back. As you can see, you could receive about 0.8% of your DNA from your 5th great-grandparents.
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How Many Years Ago Does Your Ethnicity Appear?
The final column in the table above suggests how many years happened between each generation. I used 25 Years to keep the math simple.
By eight generations, you would likely find your ethnicity your 6th great-grandparents about 200 Years ago.
That would be around the early 1800s where many records cease to exist for your ancestors. Either they were never created or have been destroyed. While you might be able to find a nice paper trail back to these sixth great-grandparents, it's unlikely that you're going to necessarily find a paper trail for your 7th to 10th great-grandparents.
Applying Ethnicity to a Generational Chart
Perhaps you have 2% Ashkenazi Jew heritage. As you look at this table, you might think this would fit with your fourth great-grandparents. One of your 64 fourth great-grandparents who lived perhaps 150 years ago might have been Ashkenazi Jewish.
If only this is how DNA was passed down and ethnicity was recorded, you could confidently start searching for your Jewish fourth great-grandparents to find who that Ashkenazi Jewish ancestor might be.
But there's a problem with this, and that problem comes up in a couple of different ways.
Be sure to listen as I explain the problems more fully in this video.
Ethnicity Estimates Aren't Exact, Creating Problems Identifying Your Ancestors
The first problem with identifying how far back on your family tree an ethnicity percentage appears stems from ethnicity results' inexactness.
While we inherited 50% of our DNA from our parents, we don't get 25% of our DNA from each of our grandparents. There's a range that we could receive.
While each set of grandparents will add up to 50 percent, but you might have 22% from a grandfather and 28% from a grandmother on one side. Now, that adds up to 50%, but neither one of those is 25%. The range of inheritance for your grandparents is about 20 to 30 percent.
As we go down even further back in time, we see that that range extends quite a bit. As shown in the video, the ranges began to overlap.
For instance, an inheritance between 3 and 7% could represent your 3rd, 4th, 5th, or 6th great-grandparents. That means instead of look at your 64 4th great-grandparents to find out who has a particular heritage, you now need to add:
32 3rd great-grandparents
64 4th great-grandparents
128 5th great-grandparents
256 6th great-grandparents
By having inheritance percentage ranges, the number of potential people this one ancestor could have ballooned into quite a number. This is the first problem that we see with this generation inheritance table.
Estimating a Time For Your Ancestors is Difficult
On my table shown above, I had used 25 to represent an average length between generations. It's a nice average, but your family is probably not average, just like my family is probably not average. It may be that that generation was shorter. Or it may be that it was quite a bit longer.
For instance, these approximate years for your parents might be 20 to 40 Years ago, depending on when you were born. I happen to have been born when my parents were about 26. But my youngest child was born when my wife and I were in our 30s.
Since the generations can vary quite a bit over time, the problem of isolating a time frame of when your ancestor lived is compounded.
Instead of reaching our 6th great-grandparents in 200 years, it may take 240 years. For Americans, that's when the United States was founded. The eighth-generation now may take 320 years to reach. If you think finding records 200 Years ago is difficult, add another 120 Years to that. Then see how difficult finding records is for that time period.
How Our Ethnicity Is Calculated Makes Pinpointing When in The Past It Appears Difficult
The last thing that we have to be worried about is how those ethnicity percentages are calculated. And for this, I can only just say that we always have to remember that we have two chromosomes. We have a chromosome from our father, and we have a chromosome from our mother.
For each one of those 22 chromosomes, commercial genetic genealogy companies don't know which letters go to which chromosome. They don't know which ones are for the paternal. They don't know which ones are for the maternal. So, they're all mixed together.
We might seem to have a slightly different ethnicity than we had planned because of how DNA sequences. In some cases, it might look like a very different ethnicity than our parents by themselves.
Should You Use Ethnicity to Pinpoint Your Ancestors?
For the most part, when you initially explore your ethnicity results, don't worry about ethnicity percentages below 5% in most or 2% in some cases.
The difficulty in determining where these small percentages appear on your family tree is quite challenging.
That doesn't mean that these small percentages won't be resolved. But it's much more difficult to figure them out, particularly if you don't already have a well-developed family tree.
If you don't already have a family tree that is very well documented for five or six generations back. I wouldn't worry about these small percentages for separate ethnicities. But if you have gotten a very good documented tree and you want to try to tackle this. It might be a fun challenge for you.
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