Y-DNA is carried by men. Merchant seamen from Sweden, c 1900 Most of genetic genealogy boils down to a matchmaking game, and Y-DNA is no exception. When you receive your results, it will likely look like gibberish - just a bunch of numbers. Since it's still cost-prohibitive to test our entire genetic makeup, these tests rely on selected markers, which can be thought of as landmarks in the landscape of our DNA. Genealogists have piggybacked off the efforts of population geneticists who have identified markers that are highly variable - ones that are useful for distinguishing between peoples and even individuals. Your results will be presented as a number for each one of these markers, and it's these numbers (representing how often certain genetic patterns repeat themselves) that are used for finding matches.
When you use a conventional genealogy database and enter 'John Smith,' the system looks for matches for each letter: J-o-h-n . . . This is exactly what happens with genetic genealogy, only numbers are used as the basis of comparison. Fortunately, all commercial testing companies have databases that automatically generate a list of matches for you. Provided you signed a release, you can then communicate with your genetic mates. Assuming you've joined one of the thousands of surname studies that already exist (try entering the following terms into a search engine - 'genealogy, DNA, surname' to see if there's a project for your name), you'll want to look for matches among your fellow participants. If you want to extend the search still further, you can enter your results in free, public access databases such as www.ybase.org, www.smgf.org and www.ysearch.org and look for matches.
So what does a match mean? It means you share a common ancestor with that person. This kind of testing can't tell you that your most recent common ancestor is your mutual great-great-great-grandfather, but you know for sure that your lines converge at some point. In most surname studies, clusters of genetic mates emerge, and these folks become your research pals. If you're especially lucky, you'll find yourself in a cluster with others who have already done a lot more homework than you. I recently persuaded a man named Jim Shields to join the Shields project of which I'm a member, and he matched another participant perfectly. The other fellow had researched the family for 27 years and knew exactly where Jim fit in, so Jim suddenly had 450 new relatives! And while I can't say this is an every day experience quite yet, the databases are finally achieving critical mass - that is, there are now enough of us getting tested that this kind of outcome will become increasingly common.
If you are contemplating a Y-DNA test, I would suggest that you select at least a mid-resolution test - a test with more than 20 markers. While tests with fewer markers are less expensive, they too often lead to false positives. You may match someone perfectly at 10 or 12 markers and both upgrade to 43, only to learn that you now only match on 33 of those 43 markers. In other words, your initial match was misleading.
Testing options: mitochondrial DNA (mtDNA)
After tiptoeing into the world of genetic genealogy with a Y-DNA test, many become curious to see what else they can learn, so they move on to mitochondrial DNA. Many think of mtDNA as the maternal version of Y-DNA, and while there are certain parallels, it's important to understand the differences - starting with the mode of transmission. MtDNA is passed from mothers to both their sons and daughters, but the sons don't pass it on. This is fortunate because it means all of us - male and female - can take this test ourselves. As with Y-DNA, our test represents those who came before us, only in our maternal line - our mother, mother's mother, mother's mother's mother, etc.
But at this point, mtDNA is not quite as genealogically useful as Y-DNA. This is because it's largely been considered more of a deep ancestry test. If you're familiar with Dr. Bryan Sykes' book, 'The Seven Daughters of Eve', you're aware that the basic premise is that 95 percent of those of European origin can trace their maternal roots to one of seven women who lived between 10,000 and 45,000 years ago. When you take an mtDNA test, you're learning which one of these 'daughters of Eve' you descend from (and incidentally, there are about 36 or 37 on a global basis) - and most companies will provide a color map showing roughly how and when your branch of the world's maternal family tree (referred to as your 'haplogroup') migrated out of Africa.
That's wonderful to know from an intellectual curiosity standpoint, but it usually doesn't tell you much about your recent roots. My maternal Irish forebears, for instance, have passed the H haplogroup down to me. H happens to be the most common in Europe (apparently her maternal descendants were the most successful in reproducing, so roughly 30-40 percent of Europeans are also H), so I have literally millions of maternal cousins.
Fortunately, however, recent research has revealed that there's greater variety in mtDNA genetic signatures ('haplotypes') than previously thought, and this suggests that it will be of greater genealogical value than we had imagined. Also, a few companies have recently introduced full sequence mtDNA tests, so in the not-too-distant future, the matchmaking game for mtDNA may well be as effective as it is with Y-DNA.
MtDNA also has a role in dealing with specific genealogical conundrums. For instance, if your great-grandfather had 15 children by three wives, and you can't quite assign all the children to the correct mothers, you might be able to test direct line maternal descendants of a few of the daughters involved and back-door into their respective mothers. It takes a little strategizing, but it's possible! MtDNA is the tool that scientists most frequently rely on for history mystery situations, such as the recent identification of the Titanic baby as Sidney Leslie Goodwin of Fulham, west London.
Should you opt to take an mtDNA test, I suggest seeking one that covers both HVR1 and HVR2 - 'HVR' standing for hyper-variable region. Testing only HVR1 will produce low resolution results and probably more matches than most would be interested in investigating, whereas testing both regions will result in more precise results and a narrower field. Of course, if you've got deep pockets, you can go ahead and test your entire mtDNA sequence, but you'll be waiting for a while to play the matchmaking game since this is so new that very few have taken such tests.
Testing options: ethnic tests
MtDNA is passed down the female line. What could yours reveal? 'Ethnic tests' isn't a formal category of genetic genealogy, but it's a convenient way to refer to a variety of tests that mostly reveal something about one's geographic or ethnic origins, such as African, Viking, Cohanim (Jewish priesthood) and Native American tests.
In general, it's wise to be slightly more wary of these tests than others because it's not realistic to expect our DNA to neatly map to present-day countries or peoples. It's true that there are some fairly strong correlations between certain genetic signatures and ethnic groups (Cohanim comes to mind), but these associations can be hard to interpret and there will always be exceptions. DNA has been around far longer than national boundaries, and mankind has been on the move and intermingling for millennia, so it's a bit of wishful thinking to look for tests to definitively classify your paternal line as Italian or Estonian or Welsh.
Having said this, there's a place for such tests, provided you understand the limitations. As with the tests already covered, ethnic tests do not explore your entire family tree and genetic makeup. Most come in a Y-DNA or mtDNA version (or both) and test only one branch of your family tree.
And your results may surprise you. In the case of African ancestry tests, for example, approximately 25-30 percent of those tested will learn that their paternal line is European in origin. This is the legacy of plantation society coming down to us in our genes, and was seen in BBC's 'Motherland: A Genetic Journey'.
In the other 70-75 percent of cases, some geographic or tribal affiliation can be provided based on where one's genetic mates reside in Africa today. But Africa is the cradle of mankind, so we've had longer there to move around than on any other continent - so the notion that one's maternal or paternal genetic signature will be found in only one location in Africa today is somewhat optimistic. A recent American television series, African American Lives, involved the testing of nine celebrities, and as the results were revealed, almost all discovered that they have genetic cousins in several locations in Africa. So while it's a definite improvement over what had been available previously to learn about one's African origins - that is, virtually nothing - the results should be taken more as an indication than an absolute.
Testing options: biogeographical tests
