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DNA and Social Networking

A Guide to Genealogy in the Twenty-First Century

The History Press

The basic principles

... the idea that within each of our body cells we carry a tangible fragment from an ancestor from thousands of years ago is both astonishing and profound. That these pieces of DNA have travelled over thousands of miles and thousands of years to get to us, virtually unchanged, from our remote ancestors still fills me with awe, and I am not alone.

Bryan Sykes, Blood of the Isles

It is now over ten years since the first DNA tests for the family historian came on the market. DNA testing is no longer a tool deployed by a few brave pioneering surname project administrators, but is rapidly becoming an essential part of the research process for many genealogists. In the early years there were just a few basic low-resolution tests available at comparatively high prices from a handful of companies. In the intervening years the range of tests available has grown and prices have dropped to a more affordable level. The number of companies offering DNA tests has also expanded. Today around a million people from around the world have had their DNA analysed, either for genealogy purposes or to learn more about their deep ancestry. We have not yet reached the stage where a DNA test is ordered by everyone as a matter of routine when they begin their family history research, but most people are at least aware of the possibilities of DNA testing, even if they do not fully understand the process and have not taken a test themselves.

All humans share over 99.5 per cent of their DNA. It is the few differences in the remaining 0.5 per cent of our DNA which distinguish us from each other. A DNA test will look at those few genetic markers in our DNA that do vary from one person to another. In general terms the more DNA we have in common with another person the more closely related we are, and the more markers that can be measured the more accurately the relationship can be predicted. This brings us to the first important point which relates to all DNA tests. A DNA test on its own reveals very little. The value of the test lies in the comparison process, and the more people you can compare your results with the better.

Types of test

When the first genetic genealogy tests became available in the year 2000 there were two different types of test that could be purchased: a Y-chromosome (Y-DNA) test and a mitochondrial DNA (mtDNA) test.

A Y-DNA test explores the direct paternal line, that is, your father, your father's father, your father's father's father, and so on back in time. In most cultures the Y-chromosome usually follows the same path as the surname. For this reason, the Y-DNA test is the most popular and most useful test, and is usually the first exposure that family historians will have to DNA testing. A Y-DNA test can only be taken a by a man, as only men inherit a Y-chromosome. Women who wish to explore their surname through DNA testing, therefore, need to recruit a male relative, such as their father, brother, uncle or cousin, to take a test on their behalf. The first Y-DNA tests only looked at 10 or 12 genetic markers. Today a standard Y-DNA test will analyse a minimum of 37 markers and it is possible to be tested on 100 or more markers.

A mitochondrial DNA test is a mirror image of the Y-DNA test and follows the direct maternal line – your mother, your mother's mother, your mother's mother's mother. Both males and females inherit mitochondrial DNA from their mothers, but only the female can pass it on to the next generation. An mtDNA test can, therefore, be taken by both men and women. The early mtDNA tests looked at a small number of locations in the most variable region of the mitochondrial genome. Today the gold-standard mtDNA test is a full sequence of the entire mitochondrial genome.

The Y-chromosome and mitochondrial DNA are passed on virtually unchanged from father to son and mother to child. They effectively contain a historical record of the DNA, not just from our recent ancestors but from our ancient ancestors on the paternal and maternal lines going back for thousands and thousands of years. Y-DNA and mtDNA tests are, therefore, used not just by family historians but also by anthropologists and population geneticists who are endeavouring to reconstruct the migratory paths of our distant ancestors as they left Africa and spread out to populate the world. Consequently, these tests come with an added bonus as they will not just help with your family history research, but will also provide some insight into your deep ancestry on your direct paternal or maternal line.

The third type of test used by family historians only came onto the market at the end of 2009 and is currently available from just two companies: 23andMe and Family Tree DNA. This test analyses hundreds of thousands of autosomal DNA markers and can help us to explore all the lines on our family tree. We inherit a mixture of autosomal DNA from both our parents, but it is shuffled up and diluted with each new generation, crisscrossing all the branches in our family tree. Although an autosomal DNA test can be used to help with our research on all our family lines, it is most effective for finding relatives within the last five generations or so. In some cases it can help locate relatives within the past five to fifteen generations. These tests can be taken by both men and women.

Uses and limitations

The uses and limitations of each different type of test will be explored in detail in the following chapters of this book, but we will first of all take a look at a few of the basic principles that apply to all of the tests. Firstly, it needs to be made clear that a DNA test is not a magic solution and will not provide you with an instantaneous family history. A DNA test is just one tool which can be used as an aid to research, and it works best when it is used in conjunction with traditional documentary research. If you are lucky you might get a match with someone who is researching the same line as you and who can supplement the information that you already have. A DNA test can also, in some cases, save time and money by providing a narrower focus for your research. If, for example, you have reached a brick wall with your research in London but your surname is found in many different counties, a Y-DNA match with a well-documented line from a specific town or parish will enable you to target your research on one particular county rather than having to scour records across the whole country.

As DNA testing is essentially a match-making game, the success of a DNA test depends on whether or not you get any relevant matches. The chances of getting a match very much depend on who else is in the database. If you test with a long-standing surname project, which has representatives from most of the trees for the surname, you will have a good chance of finding a match. If there is no project for your surname, or the project only has a few members, you might be in for a long wait before you learn anything from your DNA test result. Some of the American-led projects only have participants from the US, and even if you do have a match it will not be particularly meaningful as your match is unlikely to know where in the UK his line originated. The autosomal tests from 23 and Me and Family Tree DNA are still both very new and it will take time for the databases to build up in size. DNA testing is, therefore, very much a question of numbers, and the more people who participate the more we will learn. Many people do simply order a DNA test just to add their results to the company's database and see if they get any matches, but if you wish to have an immediate return on your investment it is better to test within a structured surname project or have a hypothesis in mind and select the appropriate candidates in advance for testing.

One important limitation of DNA testing is that it is very good at confirming that two people are related, but it will never tell us the name of the ancestor we share in common or when he or she lived. You are instead given a range of probabilities as to the timeframe when the common ancestor might have lived. The accuracy of the prediction also depends on the resolution of the test. If two men have identical Y-DNA results with a low-resolution test comparing a small number of markers, the results might indicate that they have a 90 per cent probability of sharing a common ancestor within the last twenty-four generations. A high-resolution test with more markers might perhaps give a 90 per cent probability of sharing a common ancestor within four generations. A 90 per cent probability also means that there is still a 10 per cent chance that the match will fall beyond the expected range.

Who to test?

The choice of who to test is partly decided by the type of test which is being taken. Both men and women can take an autosomal DNA test and a mitochondrial DNA test, but only a man can take a Y-DNA test. If a choice of candidates is available it is always preferable to test the oldest generation, but this is especially important for the autosomal DNA tests, which work within a more limited timeframe. What happens, however, if the person you would like to take a DNA test is no longer alive? People often ask if it is possible to extract DNA from a stamp licked by a deceased relative, a locket of hair, fingernail clippings or other similar items. Sadly, in nearly all cases, the answer is no. In the first place there is the risk of contamination, and there is consequently no absolute guarantee that the DNA is from the required person. Secondly, such testing is expensive as it has to be carried out in a specialist laboratory, and the success rate is low. To extract DNA from hair, the hair shaft is required. Even if any DNA can be extracted, it is highly likely that the pieces of DNA you need will not have survived. There is a greater chance of success in recovering mitochondrial DNA because there is much more mtDNA in each cell, whereas there is only one Y-chromosome, but for genealogy purposes it is usually the Y-DNA which is needed. The other related question which sometimes arises is whether or not it is possible to exhume a body in an attempt to extract DNA. Here the chances of success are even lower as DNA degrades rapidly over time, especially if it has been exposed to the elements. There is also a further hurdle to be overcome as permission is required from the church authorities before any exhumation is allowed, and it is rare for such permission to be granted. In view of all these difficulties, if you are considering getting a DNA test done on a relative it is very important to get the testing done while they are still around to provide the sample.

Choosing a testing company

Once you have decided which test you wish to take, the next stage will be to decide on a testing company. If you are considering taking a YDNA test, or getting a relative to test on your behalf, in most cases the choice will be dictated by the testing company hosting the relevant surname project. If there is no pre-existing surname project and you are interested in starting your own project I have looked at some of the issues to consider in Chapter 6. There is more flexibility with a mitochondrial DNA test, but there are many advantages to be gained from testing with a company with a large database which hosts geographical and haplogroup projects in order to maximise the chances of finding a meaningful match. These issues are explored in detail in Chapter 4. The new generation of autosomal DNA tests are reviewed in Chapter 5. The choice of company will very much depend on whether you are more interested in taking the test for health or ancestry purposes. A list of testing companies is provided in Appendix B along with brief descriptions.

It is important to remember that the DNA testing market is constantly evolving. Some companies have been at the forefront of the latest developments and continue to introduce new tests and extend their product offerings. In contrast, some of the smaller companies that appeared to be a good choice a few years ago have been taken over or have gone into liquidation. The range of tests offered will be an important consideration. It is not always easy to predict in advance the additional tests that might be required, but if you test with a company which only offers a limited range of tests, if you need to upgrade and the test you need is not offered, it would then be necessary to pay to be retested elsewhere. It is always best to get recommendations from other people who have taken DNA tests and to learn from their experiences. The best way to do this is to make use of the resources, such as mailing lists and forums, listed in Appendix A.

Taking a DNA test

Having decided on a testing company, the actual process of taking a DNA test is very straightforward and simple. There is no need to visit a doctor or have a blood sample taken. The DNA kit is sent out in the post and everything can be done in the comfort of your own home. The kit consists of some small brushes that look rather like mini toothbrushes and a few vials of preservative. The brushes are used to scrape some cells from inside your cheek. It is a completely painless process – the most difficult part is refraining from eating and drinking for at least an hour beforehand! Once the swab has been taken, a plunger is pressed on the brush to release it into the vial. The pots are then sealed up and go back in the post to the testing laboratory. You will usually be asked to provide samples to fill three vials. One testing company, 23andMe, collects DNA in a different way, and requires you to spit into a container. Whichever method is used, once your kit has been received in the lab, it will take anything from four to eight weeks to receive your results. All the major companies will allow you to access your results online and will provide various educational resources to help you to understand your results.

Having discussed the basic principles, we will now move on to explore the different types of test in depth, beginning with the Y-chromosome DNA test and its particular application within surname projects.

Surnames and the paternal line

The most popular and widely used DNA test for family history purposes is the Y-chromosome DNA test, colloquially known as a YDNA test. The Y-chromosome is passed on from father to son and carries the gene which determines the male sex. Conveniently for the family historian, the path of Y-chromosome transmission usually corresponds with the inheritance of surnames, making the Y-DNA test a very valuable tool as an aid to traditional documentary research. For family history purposes Y-DNA tests are usually co-ordinated within surname projects. Commercial Y-DNA tests first became available in the year 2000. By the end of the decade several hundred thousand men had had their Y-DNA tested, and there were in excess of 6,000 surname projects. Women cannot, of course, take a Y-DNA test as they do not inherit the Y-chromosome. Most women will, however, have a father, brother, uncle or cousin who can take the test in their place.

The Y-chromosome is passed on from father to son virtually unchanged. Indeed when scientists first began to explore the Y-chromosome they found so few differences that it was thought that it would not be very useful for genealogical or evolutionary studies! Gradually, however, as the sequencing technology improved and new techniques were developed, scientists began to spot patterns in the millions of letters that make up the Y-chromosome and discovered that there were particular locations or 'markers' which did sometimes change. These markers are known as short tandem repeats (STRs). A number of studies have been published comparing these markers between father and son to establish the rate of change – the mutation rate. It has also been discovered that some markers mutate at a faster rate than others. Once the mutation rates have been established for the various markers it is then possible to infer the relationship between two men purely on the basis of their DNA results and the number of differences between them. Fortunately, we do not have to worry about doing any complicated calculations ourselves. The testing companies do all the maths for us and will provide you with a list of your matches in their database, together with an estimate as to the time when you most probably shared a common ancestor.

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Excerpted from DNA and Social Networking by Debbie Kennett. Copyright © 2011 Debbie Kennett. Excerpted by permission of The History Press.
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