Ancestry Magazine

Rich or poor, we all have an amazing inheritance residing in our cells, a legacy that has been passed down through thousands of generations. It’s contained in special structures called mitochondria, which are responsible for energy metabolism. Each cell has hundreds of thousands of these mitochondria, and each mitochondrion has several DNA molecules.

Mitochondrial DNA is essential to our lives. But mtDNA also tells a story about the lives of our ancestors.

MtDNA isn’t the only DNA to tell a story—the DNA found in the chromosomes in the nucleus of our cell tells a story, too, but it is comprised of jumbled bits and pieces that could have been inherited from any one of our ancestors. The mtDNA story line does not meander; it is a straight shot back to one woman, nicknamed Mitochondrial Eve.

The reason mtDNA takes such a direct route is that it is contributed by the egg, not the sperm, so the only source of mtDNA is the mother who received her mtDNA from her mother, who got her mtDNA from her mother, and so on back for countless generations. The mtDNA of everyone alive today eventually converges with one woman, Mitochondrial Eve, who lived between 100,000 and 200,000 years ago. She was not the only woman alive at the time, but she is the only one who has had an unbroken line of daughters clear through to today.

Not Quite Perfect

Eve’s daughters copied her mtDNA faithfully. But on occasion, as generations passed, a small variation would creep into one of her descendants. This change or mutation was copied just as faithfully for many generations, like a favorite family version of a classic recipe, until another mutation occurred. Other lines of descent then placed their own distinctive stamp on the recipe.

Our mtDNA today contains a cumulative record of all those changes, and by studying the mtDNA of people around the world—and their associated mtDNA mutations—it’s often possible to trace our mtDNA to a specific geographic region and even get a rough time estimate of when our ancestors were there.

Clusters of Family

The individual mutations in your DNA set you apart from others and are called your “haplotype.” And people who share particular patterns of mutations in their haplotype fall into clusters called “haplogroups.” Some haplogroups are common in Africa, others hail from Europe, and still others are linked to Asia and the Americas.

Haplogroups describe a person’s “deep ancestry” dating from thousands of years ago, but that’s not the end of the story. Mutations within a haplogroup occur from time to time, creating sub-haplogroups. Each sub-haplogroup will include some individuals with additional mutations, creating additional sub- sub-haplogroups. Some people find they have sets of mutations so rare that the combination has never been recorded before.

Reading Between the Letters

Results of an mtDNA test seem cryptic at first glance, just a boring list of numbers and letters. My partial results read 16293G 16519C. The numbers refer to the position in the mtDNA molecule, and the letters refer to bases—chemical units that make up all DNA molecules.

Results are compared to the Cambridge References Sequence, or CRS for short. There’s nothing special about the CRS—it was simply the first mtDNA to be sequenced.

Matchmaker, Matchmaker, Make Me a Match

Just knowing the coded results of an mtDNA test won’t help you much. Instead you need to understand more about what you’re looking for. With mtDNA testing, your goal is to find one of two things: genealogical information or geographic points of origin.

Genealogically, random matches of mtDNA rarely result in a documented family connection. However, non-random matches are a different story. For example, say you believe that a woman in your family tree is related to a woman in your best friend’s family tree. Using mtDNA and some female-line descendants of each of those two women, you can test your theory.

Geographically, mtDNA is also valuable—your haplotype can point you to a broad continental origin: Europe, Africa, Asia, or America. Sometimes that alone is enough to inspire a spectacular genealogical research journey.

However, most people hope for a little more precision about their ancestral stomping grounds. This is especially true for those tracing tribal roots—both African and American Indian—where the lack of a paper trail can thwart the most determined efforts. Companies specializing in African or American Indian roots have assembled large databases of samples from tribal groups, but even those databases are still a drop in the bucket. Migrations occurred within Africa and the Americas, so a given haplotype is not necessarily confined to a small region—even if you learn you have a common haplotype, you may also learn that it’s found in multiple tribes. On the other hand, a rare haplotype may not serve any greater purpose—you may discover that it has not yet been cataloged.

Geography can cause problems for European roots as well. For instance, back in 1998, the Mitochondrial DNA Concordance listed only four matches for my haplotype: two in Portugal, one in the Basque country, and one in Finland. Since that time, studies located in the British Isles and Germany have uncovered the same haplotype. My direct line ancestors could have come from any or even all of those places, or they could have come from some place that hasn’t been studied yet.

Collecting Living Cousins

One of the criticisms of mtDNA testing (and Y-chromosome testing, for that matter) is that our own mtDNA represents only one of our many ancestral lines. But that brings up the benefit of combining DNA research with traditional family history research—when we know our extended families, we also know where to turn when we don’t want to stop with just ourselves.

Most people can get an even bigger picture of who they are by recruiting cousins to represent other lines. Our cousins have inherited different portions of the DNA story, and if we can find the right cousin, we can study the chapter that applies to any position on our pedigree chart. Plus, searching for distant cousins has always been rewarding—who knows which descendant might have inherited the family Bible or pictures or letters. So even if the “right” cousin proves genetically elusive, all of the effort spent finding that cousin isn’t wasted.

The genealogy bug strikes people at different ages, but it seems that no matter when we start, we always wish we had started sooner. There are so many questions to ask and sometimes it seems as though we have so little time. Some families already have a “designated genealogist,” who is the custodian of family figures and lore. Now there is a new task for those dedicated people—recording the DNA before a line dies away.

Ann Turner is the coauthor of Trace Your Roots with DNA. She can be reached at DNACousins@aol.com