How Far Back Does Ancestry DNA Testing Go?

Ancestry.com claims that their ethnicity estimates go back “hundreds to more than a thousand years”.

Can an Ancestry DNA test really go back 1,000 years? This article will show how this is valid for some customers but won’t be for others.

If you’re building your family tree, Ancestry.com claims that their DNA features can go back to nine generations. My survey of Ancestry users found that a limit of seven generations is more realistic.

The first half of this article looks at the ethnicity estimates. Then we’ll examine how far back the DNA matching features can take you within your family tree.

Different Ancestry Claims For How Far Back Their Ethnicity Estimates Go

You will find statements in different places on the Ancestry.com website with slightly different answers to the question: how far back does Ancestry DNA testing go?

a few hundred or even a thousand years ago

Ancestry.com FAQ

Up to 1,000 years

Ancestry.com “Getting Started” page

AncestryDNA genetic ethnicity estimates go back hundreds to more than a thousand years

Ancestry.com help page

It’s possible that the Marketing Department got a bit too excited about these projections. I wanted to check if the website claims were exaggerated, so I read the company’s scientific white papers.

This is what the Ancestry Science Team says:

The AncestryDNA® science team has developed a fast, sophisticated, and accurate method for estimating the historical origins of customers’ DNA going back several hundred to over 1,000 years.

Ancestry.com White Paper 2020

Lower and upper end

To recap, the lower range is claimed as:

  • A few hundred years
  • Hundreds of years
  • Several hundreds of years

And these are the claims for the upper range:

  • A thousand years ago
  • More than a thousand years
  • Over 1,000 years

Pulling all these together, I think it’s fair to summarize Ancestry’s current claims like this:

Ancestry.com claims that their ethnicity estimates go back to at least two hundred years up to about a thousand years.

Can we believe Ancestry’s upper end of one thousand years?

To put this into context, a thousand years represents about 40 generations. This raises an immediate objection.

We know that Ancestry estimates our ethnicity by comparing our DNA to other living (or recently living) people.

Let’s say your DNA is 100% similar to a small group of English DNA testers who have a documented family tree that goes back to the 1600s.

This is getting to the limit of genealogical evidence. Most Irish people are lucky to get back to the 1800s.

But even the 1600s only bring us back 420 years. Why does Ancestry claim they can use DNA to get back over twice as far – to a thousand years ago?

Before I delve into this, I want to take a quick look at how Ancestry’s claims have changed over the years.

Current claims are more modest than earlier versions

The previous quote from a white paper was from a document published in 2020.

However, Ancestry’s first white paper on their ethnicity estimates was published in 2013. They had a completely different description of the time range:

We provide our customers with an estimate of the ancient historical origins of their DNA.

Ancestry.com 2013 White Paper (outdated)

Ancient?  We would usually consider that to be a lot older than a mere one thousand years.

If you’re interested, I have a tutorial that shows you how to compare your Ancestry DNA results to neanderthal and other ancient samples.

The current white paper and their website descriptions no longer refer to “ancient historical origins”. They’ve walked back their claims to an upper limit of about a thousand years.

How Far Back Does Ancestry Ethnicity Really Go?

Does Ancestry’s ethnicity estimate really go back a thousand years (or more)? The answer will be yes for some people and no for others. Let’s take a look at what’s behind their claims.

In the next section, I’ll go through the scientific explanation as to why you inherit less and less DNA from each generation of your ancestors.

Here, I’ll simply say that the further back you go, the more chance there is that you don’t inherit any DNA from one of your ancestors. Take a look at the tiny numbers in this table as you go up the generations…

How much DNA do you share going back generations?

GenerationHow Much Shared DNA?Percentage
1how much DNA do you inherit from a parent?50%
2how much DNA do you inherit from a grandparent?25%
3how much DNA do you inherit from a great-grandparent?12.5%
4how much DNA do you inherit from a great-great-grandparent?6.25%
5how much DNA do you inherit from a 3rd great grandparent3.125%
6how much DNA do you inherit from a 4th great grandparent?1.56%
7how much DNA do you inherit from a 5th great-grandparent?0.78%
8how much DNA do you inherit from a 6th great-grandparent?0.39%
9how much DNA do you inherit from a 7th great-grandparent?0.20%
10how much DNA do you inherit from an 8th great-grandparent?0.10%

Ancestry’s 8th cousin limit

Ancestry’s most distant cousin label is “5th-8th cousin”.

If we take them at their word that they can detect shared DNA between 8th cousins, then an 8th cousin would go back nine generations.

Nine generations represent about 225 years. This corresponds with Ancestry’s stated lower range of a few hundred years.

But if this is getting to the limit of detectable DNA, how can they say that their ethnicity estimates go back a thousand years?

Ancestry’s assumptions

The Ancestry Science Team is working on the assumption that people living over two hundred years ago were far less likely to migrate to other continents or regions.

The team includes experts in historic population migrations. Their ethnicity algorithms were developed to take known migrations into account.

This lets them identify specific regions where DNA patterns that go back two hundred years ago will probably represent a further eight hundred years of settled communities.

However, there are other regions that experienced waves of inward migration from differing areas over time. This is reflected in the probability ranges in your ethnicity estimates.

When Ancestry’s ethnicity estimates go wrong

Can it happen that one of your great-grandparents hails from a region that is completely absent from your Ancestry ethnicity estimate? Yes, it can.

The problem for Ancestry’s DNA test is that you may not inherit any autosomal DNA from one of your fourteen great-grandparents. And this may be the great-grandparent that immigrated from a different region.

If you and a sibling both tested, you may find that each of you has regions that the other does not. I have a separate article with real-life examples on how Ancestry’s ethnicity estimates can be different for siblings.

How Many Generations Can Ancestry DNA Identify In Your Family Tree?

Let’s look first at theoretical predictions from Ancestry.com and independent academic studies.

Then I’ll look at some real-life results which don’t quite go as far as Ancestry suggests.

Theoretical claims from Ancestry and independent academic studies

An academic study was published in 2012 that estimated the chances of DNA tests detecting inherited DNA by generation.

The 2012 study suggested that there was less than a 50:50 chance of detecting shared DNA at five generations (that would be fourth cousins. And their estimates dropped to 0.24% at nine generations (eighth cousins).

But what does Ancestry say? In 2020, they were more bullish about their detection rates. Their white paper estimated that their algorithms detect 71% of fourth cousins and 0.9% of 8th cousins.

Here is a side-by-side comparison of the academic and corporate claims:

GenerationsCousinAcademic Estimates Detectable DNA (2012)Ancestry Estimates Detectable DNA (2020)
43rd90%98%
54th46%71%
65th15%32%
76th4%11%
87th1%3.2%
98th0.24%0.9%

According to Ancestry.com, there is a tiny 0.9% chance that their DNA test will detect your DNA shared with an 8th cousin. That brings the upper limit to nine generations.

My experience with Ancestry doesn’t get near that level.

How far back does Ancestry go back for me?

If you’ve tested with Ancestry, you’ll know that the DNA match list goes down as far as their category of “5th-8th” cousins.

Personally, the furthest DNA relative I’ve been able to identify in my family tree is a 3rd cousin once removed. Our common ancestors are my 3rd great-grandparents.

However, Ancestry’s DNA results provide predictions of possible ancestors. Ancestry has a DNA feature called ThruLines which attempts to predict common ancestors between you and your matches.

The predictions can be completely wrong, but the feature can be very helpful. (We have an article with tips on evaluating ThruLines).

The furthest DNA relative that Ancestry predicts for me is through my 4th great-grandparents. This is six generations back, so it’s still not getting nine generations.

However, it would be unfair of me to judge Ancestry’s DNA test on my own results. Irish heritage is challenging to research back before the mid 18th century.

So, I reached out to a selection of clients I’ve helped with Ancestry research.

My survey of Ancestry users

I asked twenty-seven Ancestry users to filter their DNA match list to show DNA relatives of 8 cM with a predicted common ancestor.

They look like this DNA match below. Notice the green leaf icon for a suggested common ancestor:

I then asked them to look for the furthest predicted common ancestor.

Nobody had a suggested common ancestor that reached 6th great-grandparent (8 generations).

However, 86% of these Ancestry users had at least one predicted ancestor at the level of 5th great-grandparent. That represents seven generations.

This is two generations less than Ancestry’s claim of nine generations. However, I could only survey a small collection of Ancestry users. You may find that you get back a little further.

The Science Behind Why Ancestry’s DNA Tests Can’t Identify All Your Ancestors

I’ve touched on the fact that Ancestry’s DNA test cannot identify all your ancestors past four generations. You may not inherit any DNA from a great-great-grandparent.  If you’re interested in understanding why, then this section is for you!

The Ancestry DNA test is an autosomal test that examines 22 of your chromosome pairs.

For each of your chromosome pairs, you inherit one copy from your father and one from your mother.

However, the DNA in your copies isn’t identical to your parents. A process called recombination results in the random shuffling of segments of chromosomes.

One generation

The picture below is an illustration of the same chromosome pair passing from parents to two children. As you can see, the siblings don’t inherit the same DNA in the same order.

As we mentioned, each parent provides one of two of the non-sex chromosomes to their child. This means that half of a parent’s genetic material is left behind.

Losing ancestral DNA through generations

The loss of DNA with each generation means that you inherit about 25% of your grandparent’s DNA. Of course, that number gets cut in two with each generation.

But the math isn’t as easy as that. As DNA passes through the generations, segments can also break and swap between chromosomes.

By the time we get down six generations, you will not inherit any DNA from some of your 4th great-grandparents. This is illustrated in the picture below.

I’m not showing three generations in the diagram. I want you to focus on the bottom row, which is the same chromosome pair for three fifth cousins.

The sections I’ve marked as (1) show a small segment of DNA shared between two of the three fifth cousins. This small piece of DNA has passed from one chromosome of the male ancestor six generations back.

The sections I’ve marked as (2) show another small piece of DNA from the female ancestor. But this is only inherited by two of the three cousins.

And notice that the two outer cousins share no matching DNA from this ancestor at all.

What About Other DNA Tests?

23andMe is a big rival to Ancestry.com in consumer DNA testing. Both companies perform autosomal DNA testing, which means that they should be dealing with similar time frames.

But 23andMe makes far more modest claims than Ancestry.com. You can read our article on how far back 23andMe goes, which shows how they arrive at their claims of 200-300 years.

You can also upload your Ancestry DNA results to MyHeritage for free, although you may need to pay a fee to view advanced ethnicity features on the site. Check out our article on how far back MyHeritage goes.

Exploring Ancient Origins Within Your DNA

You can upload your Ancestry DNA results for free to the GEDmatch website. This gives you access to a set of tools that explore components of your DNA that date back many thousands of years.

You can use calculators that estiamte ancient Mesolitithic and Neolithic components in your DNA. GEDmatch also allows you to lower the threshold of shared DNA to review more distant DNA matches (although this may not be recommended).

You can check out all these features in our guide on how far back GEDmatch goes.

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