African American Lives
Analyzing the Evidence
The Science and the Investigators
Who am I? A Genealogy Guide
Sharing Stories
For Educators
About the Series

The Science and the Investigators
Intro Race and Science The Tests Learning from DNA
Lineage and Admixture: Testing for Ancestors: Lineage Testing
Image of a map of Africa, with lineage matches highlighted, alongside a listing of human haplotypes.
Lineage based tests focus on the two elements of DNA that are passed down from your mother and your father, mitochondrial DNA (mtDNA) and the non-recombining segment of the Y chromosome (NRY). Since these elements exist only in the male or the female and since neither recombines with any other genetic material (and is passed down with only the most minor changes from generation to generation), their genetic sequences and markers, when compared to databases, can be used to trace clear lines of matrilineal or patrilineal descent.

Think of DNA like a surname. You have a gene, which is passed down from generation to generation, just like my own name Forster was passed down from generation to generation. But my ancestor's name, 800 years ago, was not Forster but Forester, which was obviously his profession...Forester mutated or changed to Forster. And then other Forsters mutated further, particularly in southern England, to Foster. And this is something that happens in DNA as well. As the generations pass by, the DNA does not remain unchanged but diversifies into different types, which are still related but are distinct now. And the same way that genealogists today use variants of surnames to trace back an ancestral surname, the same way we geneticists use variants, or small variants, of DNA types in order to trace back ancestors which lived hundreds or thousands or even tens of thousands of years ago.
-- Dr. Peter Forster

To learn more about the processes involved in mitochondrial and Y-chromosome approaches to lineage testing, click on the images below. To learn more about what situations call for each test, take a look at the graphic on this page.

Y-Chromosome Mitochondrial DNA
find out more about Y-chromosome testing find out more about mitochondrial DNA testing

The chart below demonstrates why it's important that researchers have two types of lineage tests to choose from, and also demonstrates why DNA testing is only a partial solution to the challenge of identifying one's distant ancestors. There's more to deciding to pursue one line of testing over another than simply deciding whether one wants to track down male or female ancestors.

Chart illustrating mitochondrial and y-chromosome descent
The graphic represents four generations of a family, the present-day representatives of which are a brother and sister (the red and blue circles at the base of the tree). Working backward, mitochondrial DNA descent can be traced by the red lines; Y-chromosome lineage by the blue lines.

What becomes immediately clear is that both siblings can trace their mitochondrial DNA line back to just a single great-grandmother, and the brother can trace his Y-chromosome back to just a single great-grandfather. The other three women and men of that generation have indeed passed on genetic material to their descendants, but that information is carried only in the 22 autosomal DNA pairs of the genome, and that material is not directly traceable by any current testing method.

Extrapolating back further in time, you'll realize that lineage testing can indeed tell you a lot, but though the information is extensive, it comes from a very limited group of your ancestors. In fact, if you are a woman, you'll only be looking at just a single line of your descent, and if you are a man, only at two lines, out of all of your ancestors. Basically, lineage testing is capable, at least theoretically, of providing great detail about your ancestry, but at the expense of the general picture.

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