How do I trace my ancestry?
DNA tests can now be used for a wide range of applications, including the improvement of health and fitness, confirming familial relationships, and even to produce your dog’s family tree! However, one of the first applications of home DNA testing was to trace ancestry, and this has quickly become the most popular use for a genetic analysis. But what exactly is genetic testing for ancestry, and how does it compare to traditional genealogy research?
Your DNA contains markers that you’ve inherited from your ancestors, and these can be used to trace your ancestry. There are many ways in which your genes can be analysed to provide you with this information, and depending on the DNA test for ancestry you choose; you can trace your maternal genetic ancestry (the lineage of your mother’s mother’s mother etc.), your paternal genetic ancestry (the lineage of your father’s father’s father etc.) or your autosomal genetic ancestry (a mix of the DNA you’ve inherited from each of your parents).
You may also have come across the terms DNA genealogy, ‘DNA origin test’ or ‘DNA history test’, but these all refer to genetic testing for ancestry, and tests to trace ancestry fall into three broad categories: Maternal analyses, paternal analyses and autosomal analyses.
Maternal and paternal tests report on your ‘deep’ ancestry. They’ll help you understand the migratory paths of your maternal and paternal ancestors after they left Africa around 200,000 years ago, up until the thousand year period before the era of mass migration circa 1850. A maternal or paternal test may also be referred to as a DNA history test.
Autosomal tests give you a picture of your genetic heritage from the past five generations of your family. They also report on your ‘recent’ ancestors: Those that lived in the thousand year period before the era of mass migration circa 1850. An autosomal test may also be referred to as a DNA origin test.
If you’re interested in buying a DNA test for ancestry, you can check out this complete list of genetic ancestry companies.
Maternal, paternal and autosomal tests
As a human your DNA consists of 23 pairs of chromosomes in the nuclei of your cells (46 chromosomes in total) – 23 chromosomes from each parent. You also have DNA in the mitochondria in your cells which we’ll come to later.
Because your chromosomes and mitochondria are passed from generation to generation, these microscopic structures can be used to provide information about earlier generations of your family, and can help you trace your ancestry without the need for meticulous family records. Two of the 46 chromosomes in the nuclei of your cells are known as sex chromosomes and determine your gender. Females have two X chromosomes and males have one X and one Y. Chromosomes that do not determine sex are known as autosomes or autosomal DNA.
As you inherit your mitochondria from your mother, the DNA in these structures can be used to trace your ancestry on your maternal line. As only males possess Y chromosomes, these can be used to trace your ancestry on your paternal line. Approximately 50% of your autosomal DNA is inherited from each parent (it’s not exactly 50% because chromosomes can break down and recombine when you’re conceived), and as it cannot be determined which autosomes or autosomal segments you’ve inherited from which parent, autosomal DNA is used to trace ancestry that isn’t specifically maternal or paternal.
Mitochondrial genetic ancestry testing
As discussed, mitochondria can be used to trace ancestry on your maternal line. A mitochondrial DNA lineage test uses your mitochondrial DNA (mtDNA) which is inherited from your mother’s mother’s mother etc. Both males and females possess mitochondria and so everyone can undertake mitochondrial DNA testing.
There are three mitochondrial DNA regions that can be analysed using a maternal DNA lineage test. The first is ‘hypervariable region 1’, usually abbreviated to HVR1. It isn’t necessary to know what this means when taking a DNA test for ancestry, but it is important to know that the results from this analysis alone aren’t usually specific enough to be of much use. For this reason, most providers combine a HVR1 analysis with a ‘hypervariable region 2’ (HVR2) analysis to provide more specific results. An increasing number of providers will also offer to analyse your whole mitochondrial genome, covering HVR1, HVR2 and ‘hypervariable region 3’ (HVR3, aka the ‘coding region’).
A mitochondrial DNA test, sometimes known as a maternal DNA history test, will usually reveal your maternal ‘haplogroup’, a term used to describe the population group you share your maternal lineage with, whose maternal ancestors have taken a similar migratory path to yours since leaving Africa 200,000 years ago.
The more sophisticated the mitochondrial analysis, the more relatives you’ll be able to find on your maternal line (providing the company you purchased the mtDNA test from offers this feature). The sophistication of the analysis will also impact how specific the maternal haplogroup you’re given will be, which in turn affects the accuracy of the reported migratory path of your maternal ancestors.
Y chromosome genetic ancestry testing
The Y chromosome (Y DNA) can be used to trace your paternal ancestry, and so a Y DNA test is a DNA lineage test that reports on your paternal line (your father’s father’s father etc.). As only males possess Y chromosomes, only males can take this type of DNA lineage test.
If you’re female, you might be asking yourself ‘How can I trace my ancestry on my paternal line?’. Fortunately, you can still trace your paternal ancestry by asking your biological brother, father, paternal uncle or paternal grandfather to take a paternal DNA lineage test.
A Y chromosome test, sometimes known as a paternal DNA history test, is conducted to varying levels of detail according to the Y chromosome markers analysed. The two most commonly used markers are short tandem repeats (STRs) or single nucleotide polymorphisms (SNPs). Although these terms sound complicated, they essentially refer to unique sections of genes that are passed down from generation to generation. The higher the number of markers that you share with someone, the more likely it is that you share ancestors. STRs are relatively large regions of your Y chromosome, whereas SNPs are tiny insertions, replacements or deletions in certain genes. Both types of markers can be used to identify your paternal ‘haplogroup’ and your living relatives (providing the company you purchased a Y DNA test from offers this feature).
Autosomal genetic ancestry testing
As mentioned above, the 44 chromosomes that do not determine sex are known as autosomes or autosomal DNA. Genetic ancestry testing that uses autosomal DNA provides information about your origins that isn’t specifically maternal or paternal. Everyone has autosomes and so everyone can undertake autosomal DNA testing.
This type of test, also known as a DNA origin test, looks specifically at SNPs and will commonly tell you which population groups or ethnicities your DNA is associated to and in what proportions. Most autosomal tests look for 600,000 to 1,000,000 SNPs, and will find approximately 100,000. These 100,000 SNPs will be cross-referenced with the reference populations that the company has access to, and this will allow them to report on your ‘ethnic breakdown’. Like mitochondrial and Y chromosome tests, some companies will use your autosomal results to help you find your living relatives.
How do companies turn my DNA into information about my ancestry?
The primary method by which companies help you trace ancestry using your DNA is through the use of data from reference populations. These consist of modern groups of people whom are native to particular areas of the world. By looking at the DNA data collected from these populations, markers exclusive to these groups can be identified and compared to your DNA to trace your ancestry.
Each provider will use a slightly different selection of reference populations to help you trace your ancestry. Most will give you at least some information on the ones that they use, but they are much less likely to provide information on the algorithm used to compare the markers. Not only does the quality and quantity of reference population data affect your analysis, but the origin of your recent ancestors is also a factor.
For example, the European and North American reference populations used to trace ancestry are often larger (as this is where most individuals take a DNA test for ancestry), so if your recent ancestors are from these areas, your results will be more specific. Fortunately, some companies such as Chinese-based ‘WeGene’ have started to offer ethnicity DNA tests that focus primarily on Asia. Therefore, if you want to undertake genetic testing for ancestry to look for specific ethnicities in your ethnic mix, it’s worth checking that the reference populations for these ethnicities are used by the company in question before ordering (whether it’s a DNA history test or DNA origin test).
DNA data upload
Recently, several websites have emerged that offer information about your genetic heritage without your having to send them a biological sample, providing that you’ve already taken a test with one of the major companies (most notably 23andMe, AncestryDNA and Family Tree DNA). These companies offer you a free download of your DNA data after you take their test, and you can upload this information to other websites.
You might be asking yourself, ‘Why would another website give me any more information about my ancestry by analysing data that’s already been processed?’. Well, as these websites can re-analyse your markers using different reference population data and algorithms, the results you receive can be substantially different. Fortunately, many of these websites will re-analyse your data for free or at just a fraction of the cost of the original DNA test you purchased.
How much will it cost to analyse my ancestry?
The cost of genetic testing for ancestry has decreased a lot since it was first introduced, you can now buy a DNA history test or DNA origin test for as little as £59. Prices depend on the company you buy from and the type of analysis you wish to purchase. For example, an mtDNA test to trace maternal ancestry from Home DNA Direct costs £129, whereas an mtDNA test from Family Tree DNA will only cost you £65. It’s also worth noting that companies often offer packages of tests that include combinations of maternal, paternal and autosomal analyses for a discount. 23andMe is one such DNA test for ancestry that analyses all three types of DNA for £149.
The Family Finder feature
Not all genetic ancestry companies keep a database of their customers and identify your living relatives (aka ‘matches’ or ‘connections’) when you take a test. Companies with a ‘Family Finder’ feature that allows you to identify and contact your living relatives, sometimes charge more or require you to sign up for a subscription. If this is a feature that you’re interested in, make sure you check the genetic ancestry company’s website first.
It’s also worth bearing in mind that you’ll find more living relatives by testing with companies that have larger databases, especially if they have a large number of customers from your country of origin – you can often request this information from the company you wish to buy from beforehand. In order to increase the likelihood of your living relatives replying to your messages (or messaging you), we advise that you complete your profile on the genetic ancestry company’s website and upload a picture where possible.
Number of STR markers
Having seen companies refer to STRs on their websites, you might be asking ‘What difference does the number of STRs make to tracing my ancestry?’. Genetic ancestry testing companies will often give you the choice to pay for more markers for more sensitive results. Family Tree DNA is one such company and they currently offer three types of Y chromosome test: Y-DNA37, Y-DNA67 and Y-DNA111 – the numbers indicating how many STRs will be analysed. The cost of the most and least sensitive STR tests differ by about £165, the sensitivity affecting the specificity of the haplogroup you receive, and the strength of your match to the living relatives identified.
What else should I know about genetic ancestry testing?
Genetic testing for ancestry shouldn’t be considered an alternative to traditional genealogy research, and several companies let you combine both your genetic and non-genetic results (e.g. Ancestry.com) to give you the best of both worlds. A DNA history test or DNA origin test can be a great way to focus your non-genetic research, by revealing the ancestors you share with living relatives, whose names can be sought in birth, marriage, death and census records.
In terms of the results themselves, each company differs in their approach. Some companies provide interactive tools to help you trace your ancestry, whilst others provide written accounts of your ancestors’ supposed experiences throughout the ages. If you’re buying a genetic ancestry test as a gift, it’s worth looking for example reports on the genetic ancestry companies’ websites, to get a feel for how they present their results.
Genetic testing for ancestry is not exact. The fact that modern reference population data is used for the analyses means that although good estimates can be made, they cannot be definite. Markers have been identified that establish how population groups have branched and migrated in the past 200,000 years, but it’s virtually impossible to know when certain branching took place or when certain groups migrated to new areas. If you’re looking for this sort of detail by taking a test to trace your ancestry, you’re going to be disappointed!
10 October 2017
A very good service. Compliments