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Our Origins and Ancestry

An older family photoDoes your family identify with a particular ancestry? Would you like to find out whether or not that identity is true? For centuries, people have been actively gathering, preserving, and sharing their written records and passing down their oral family histories for many purposes: to trace the journey of their ancestors, to explore their heritage, or to connect with unknown living relatives. Genomics is the newest tool for looking deep into our personal histories to trace the paths of our ancestry. Direct-to-consumer genetic testing companies are now identifying the composition of your ancestry by looking at thousands of DNA markers for each person, then comparing your DNA results to DNA databases from other individuals around the world to identify common ancestors.

How does ancestry testing work? 

How does ancestry testing work? To begin with, certain genomic markers are passed only from mother to child, and thus reveal your direct maternal ancestry. Similarly, in the case of men, a number of markers are passed down only from father to son and illuminate a direct paternal ancestry. However, altogether, these markers represent a very small portion of your genome and can only reveal limited information. For example, they do not tell you about specific individuals in your ancestry – whom they were, where they lived, what they did for a living, their participation in wars, number of marriages, or size of family. And the number of generations traced depends on the design of the DNA test.

Genomics is the newest tool for looking deep into our personal histories to trace the paths of our ancestry.

Another strategy is to test a selection of thousands of markers inherited from ancestors on both sides of the family and scattered across your genome. The resulting genomic profile is compared with huge databases to find out if you have DNA markers that are common in certain populations. The reported ancestry depends on the company, the specific markers they chose to test, and the information in their databases. This method also cannot tell you who your ancestors were, only if they were related to certain population groups in the reference database.

Genetic ancestry inference yields a different picture of your ancestry than traditional, record-based genealogical research. But while the sequence of your genome can’t reveal everything about your family history and your ancestral origins, it can provide pieces of information to complement the details gathered from historical records and oral stories and traditions. Sometimes people are surprised by the findings, especially if they have identified with a certain ethnic group that does not match their genomic results. On the other hand, people who have no family records or stories may glean the only information available to them about their ancestral heritage.

Photo Credits

Family photo courtesy of Belen Hurle, Ph.D. , NHGRI

Resources

(1) What is mitochondrial DNA?  Talking Glossary of Genetic Terms, National Library of Medicine Handbook.

(2) Y chromosome ancestry. DNA Learning Center.