How far back do ancestry DNA tests go?

Ancestry tests are a fascinating way to discover more about where your ancestors came from.

Whether you want to know more about your biogeographic ancestry, or where your paternal and maternal ancestors came from, there are different types of DNA test designed to help you uncover your ancestral origins.

In this article, we discuss the different types of ancestry testing available, what these tests can tell you, and how far back they can go to look at where your ancestors came from.

What is an ancestry DNA test?

Many of us are aware of the history of our immediate family. Stories are passed from one generation to the next, giving us a large amount of information about where our parents, grandparents, or even great-grandparents came from and journeyed to.

For many of us, though, the knowledge of our ancestry ends there. Without technology to record the history of our ancestors, information about where they came from, the jobs they might’ve had, and the journeys they may have taken has mostly been lost to time.  

This is where ancestry DNA testing can help.

Ancestry DNA testing allows you to discover where your ancestors may have originated using DNA and goes back much further than the few generations that preceded you.

DNA testing for ancestry looks at variants in your DNA that can be linked to different populations of people around the world, giving you a greater understanding of your ethnic origin, geographical distribution of your ancestors, and can even show you the journey your ancestors may have taken thousands of years ago.

There are three different types of ancestry DNA tests: autosomal DNA, Y-chromosome DNA (Y-DNA) and mitochondrial DNA (mtDNA). Each test analyses a different part of your DNA and can inform you about different parts of your ancestral history.

How do ancestry DNA tests work?

Ancestry tests work by looking at the mutations (variants) in your DNA and comparing it to the mutations observed in reference populations.

We all inherit 50% of our DNA from our biological father and 50% from our biological mother. Your parents inherited their DNA in the same way from their parents, and so on. That means that lots of these variants in your DNA have been passed down through many generations.

But why are these changes in your DNA so special, and how can they give you information about your ancestors?

To explain why certain variations to your DNA are significant, let’s look at an example.

Population A is our starting population, living in area 1. A group of people (population B) decide to migrate to another area (area 2). Population B does not move back to area 1 and the remainder of population A does not move to area 2. At first, the people living in these two areas won’t be that genetically distinct from each other. However, over time, mutations in the DNA will cause the two populations to become more distinct from each other.

Ancestry tests look for specific variants in your DNA and compare them to the variants found in different reference populations around the world.

The type of information you receive about your ancestry depends on the type of ancestry DNA test you take.

Autosomal DNA ancestry tests look for variants across all your DNA, excluding the sex chromosomes. The results will tell you which population you are most genetically similar to, indicating where your ancestors are likely to have originated from.

The paternal lineage ancestry test looks only at variants found in the Y chromosome, which is passed down the paternal line, father to son, relatively unchanged.

The maternal lineage ancestry test looks for variants in the mitochondrial DNA (mtDNA). The mtDNA is special because it is inherited exclusively from the mother, although both males and females inherit mitochondria – unlike the Y chromosome, which is only inherited by males.

Paternal and maternal lineage ancestry tests can give you information about where your paternal (male) and maternal (female) ancestors may have originated from and journeyed to.

How far back do ancestry DNA tests go?

Autosomal DNA testing

An autosomal DNA test for ancestry testing looks for variants in all your DNA (with the exception of the sex chromosomes).

Autosomal ancestry DNA tests usually look for single nucleotide polymorphisms (SNPs) in the non-coding regions of your DNA. SNPs are a good target for ancestry analysis because they have a lower mutation rate than STRs (short tandem repeats – sections of short repeating sequences of DNA).

This low mutation rate means that ancestry testing can go back hundreds or even thousands of years to trace your ancestors to the place they likely originated from. This is possible by comparing the SNPs in your DNA to the SNPs of different reference populations to find out your ancestry’s likely place of origin.

Y-DNA testing

Y-DNA testing looks at variants only found on the Y chromosome. The Y chromosome is one of two sex chromosomes, the other being the X chromosome.

The Y chromosome is “special” because it is found only in males and can only be passed from father to son. Furthermore, the Y chromosome remains almost completely unchanged between generations, making it an ideal target for ancestry testing.

The variants detected in your Y-DNA will give you a haplogroup result. The haplogroup is a genetic group of people who share a paternal line, and therefore a common paternal ancestor.

As these humans began to move and settle in different parts of the world, mutations occurring in the Y chromosome led to new haplogroups forming and being passed through the generations.

Over time, more mutations gave rise to subclades within each of the haplogroups and provides more detailed information about where a person’s ancestor may have originated from.

For example, two common subclades of paternal haplogroup R are R1a and R1b. R1a is found more commonly in Central and Eastern Europe, whereas R1b is found more frequently in Western Europe.

Y-DNA haplogroups can be as old as ~200,000 years or formed just a few thousand years ago. The first Y-DNA haplogroup to exist was haplogroup A, from which all other haplogroups descended.

Y-DNA haplogroups are named A-T, with haplogroup A being the oldest and haplogroups Q, R, S and T being the youngest (approximately 25,000 years old).

Subclades within haplogroups are formed after the basal haplogroup emerges, so some subclades of some haplogroups can be very young indeed, perhaps only a few hundred years old.

Mitochondrial DNA testing

The mitochondria are structures (organelles) found within cells of the body, providing energy for our cells to use. Mitochondria are unique in that they also contain their own DNA, and this mitochondrial DNA (mtDNA) is passed exclusively from mother to child.

Unlike the Y chromosome, which is only inherited by males via the paternal line (father to son), both male and female offspring inherit their mother’s mitochondrial DNA, making it an ideal target for maternal lineage analyses for both males and females.

The maternal lineage test works in a similar way to the paternal lineage test but looking for variants in your mitochondrial DNA.

These variants are linked to different maternal haplogroups.

The first, and therefore oldest, mitochondrial haplogroup (the haplogroup at the root of the Homo sapiens mitochondrial phylogenetic tree), is haplogroup L. Haplogroup L is about 200,000 years old and, like paternal haplogroup A, is found mostly within Africa.

Haplogroup H is one of the youngest and most prolific mitochondrial haplogroups, is approximately 20-25,000 years old, and is also the most diverse haplogroup, with over 100 subclades of H* believed to exist.

Learn more: What are haplogroups?

Does ancestry DNA testing become less accurate the further back it goes?

Trying to calculate the age and origin of our ancestors is no easy task.

Scientists must combine their research in various fields to approximate age and geographical origin as accurately as possible. One of the biggest challenges that these researchers face is finding viable ancient samples to test.

Ancient remains are not easy to come by, and there is a high likelihood that any remains found won’t be suitable for DNA testing.

However, despite these challenges, scientists can estimate geographical origins and migration routes of our ancestors.

The DNA from ancient samples that are available has been incredibly informative. For example, ‘Cheddar Man’, the oldest human skeleton found in Britain, was preserved enough that DNA samples were obtained.

Scientists found that most of Cheddar Man’s ancestry could be traced back to a genetic cluster in Italy. They also discovered that he belonged to paternal haplogroup I2 and maternal haplogroup U5.

Scientists will also consider molecular clocks when attempting to estimate the age of a geographical genetic population or uniparental haplogroup. A molecular clock is a term used to describe relatively constant changes to an organism’s genome. Simply put, it can estimate how often a part of an organism’s DNA mutates (changes).

The location of where remains are found, and the materials among which they are found, can also give vital clues as to the age of a paternal or maternal haplogroup.

All this is to say that ancestry testing will never be an exact science. DNA testing only became available in the 1980s; before this time, the technology required to answer important questions about where our ancestors came from simply did not exist.

As time goes on, more evidence is uncovered, and scientific techniques continue to improve, it is likely that these age and location estimates may change slightly.

The results of all AlphaBiolabs’ Ancestry Tests are 100% accurate based on the samples we receive, and the most up-to-date scientific research available, so you can be confident in your results.

Where can I buy an ancestry DNA test?

You can order an AlphaBiolabs DNA Origins Ancestry Test, Maternal Lineage Ancestry Test or Paternal Lineage Ancestry Test direct from our accredited laboratory.

With only a simple cheek (buccal) swab sample required, these tests can give you an insight into the journey your ancestors took thousands of years ago, as well as giving you an idea of where your ancestral line may have originated.

The DNA Origins Ancestry Test is suitable for everyone and can determine your biogeographic ancestry.

Our Maternal Lineage Ancestry Test is available for both men and women, as each person inherits mitochondrial DNA from their mother.

The Paternal Lineage Ancestry Test can only be taken by males, as the test analyses DNA markers on the Y chromosome, which is only found in males.

However, if you are a woman who would like to find out more about the paternal lineage of your family, you can ask a close male relative (e.g. father, brother, father’s brother etc) if they would like to take the Paternal Lineage Test. 

For more information about our ancestry testing, speak to our friendly, knowledgeable Customer Services team by calling 01 402 9466 or emailing info@alphabiolabs.ie.