Genetic Genealogy
Genetic testing for genealogy research has transformed how people construct their family tree and research their ancestry. While genealogy by genetics will never replace more traditional genealogy tools, DNA testing can yield interesting and invaluable information about a person’s ancestry.
Genetic Testing for Genealogy Research
DNA genealogy testing can take a number of forms. The most commonly-used tests for genetic genealogy are the mtDNA and Y-DNA tests, which test for maternal and paternal heritage, respectively.
mtDNA Genealogy Testing
mtDNA stands for mitochondrial DNA, which is passed to children from their mothers. Because we inherit mtDNA from our mothers, it is not mixed with our father’s DNA. While mtDNA changes over time, it does so very slowly. Your mtDNA, whether you’re male or female, is probably identical to that of your mother’s, just as hers is a copy of her mother’s.
mtDNA is very stable over generations. If you and a suspected relative have an mtDNA match, you probably had a common female ancestor. Unfortunately, genealogy by genetics that relies on mtDNA cannot prove whether that common ancestor was your mother, her grandmother, or a woman who lived hundreds of years ago.
Y-line Genetic Genealogy Tests
The Y-chromosome is only passed from father to son, and only males have a Y-chromosome. Y-line DNA genealogy is useful to anyone researching their surname’s genealogy. Western culture traditionally traces families through the male surname.
Haplotypes are chemical variations on the Y-chromosome that differ from one male lineage to another. Y-line DNA genealogy testing can identify these haplotypes and determine if two men are related. The genetic genealogy test cannot determine exactly how the two men are related, but can indicate a common ancestor (much as mtDNA suggests a common female ancestor).
Minorities and DNA Genealogy Testing
Genetic genealogy has had a large impact on minority groups, particularly in African Americans and native Americans. Both ethnic groups have a sad history of forcible relocation and family separation, and some people see genetics testing for genealogy as a way to reconnect with a past that was taken from them.
Many Americans claim some degree of Native American ancestry. For those who want to confirm family stories, or are simply curious, DNA genealogy tests can shed light on their past.
One famous test provided evidence supporting the theory that Thomas Jefferson fathered children with Sally Hemming, one of his slaves. The researchers in this particular instance of genetic genealogy utilized Y-line DNA from the descendants of Jefferson’s paternal uncle (Jefferson has no surviving male descendants).
Genetics Genealogy Limitations
While DNA testing can uncover an amazing amount of information about your family history, there are limits to genetic testing for genealogy research.
Genetic genealogy can’t take the place of traditional genealogical research. A DNA test can’t provide you with a detailed family tree or identify the names of your ancestors (except in exceptional circumstances). A DNA test can, however, indicate a relationship between you and another person or group of persons.
The information yielded by genetic genealogy is often fascinating, and sometimes even life-changing. It’s important to remember, however, that you’re only seeing a tiny slice of your total ancestry.
What You Can Uncover With a Genetic Genealogy Tests
If you’re male, you can trace both your all-female matrilineal line through mtDNA and your all-male line through Y-chromosome DNA tests. Women can test for their matrilineal line: A DNA sample is required from a brother or father to trace a woman’s patrilineal line.
Even then, you can only trace your genetic genealogy through two of your eight great-grandparents: Your mother’s grandmother and your father’s grandfather. To gain a more complete picture, you’d need DNA samples from aunts, uncles and cousins.
Presume you manage to use DNA samples to trace all eight grandparents. First off, congratulations: Not everyone can boast such a complete genetic genealogy. You still have holes in your family tree, however, since each great grandparent’s ancestry can only be traced back through their all-male or all-female line, depending on the great grandparent’s gender.
Reasonable Expectations of Genetic Genealogy
Unavoidable gaps in genetic genealogy prompt some scientists to question whether or not ethnicity can truly be determined by DNA testing. African-Americans have sometimes been shocked to discover that their genetic genealogy seems to begin with white Europeans when traced through their matrilineal or patrilineal lines.
Critics argue such circumstances are flukes more than anything else. The information may be accurate, but it doesn’t tell you the whole story. Still, it can be a shock to receive DNA tests that throw your cultural ethnicity into doubt.
Most DNA testing facilities are very up-front about the limitations of genetics testing for genealogy research. People can find out amazing things about their ancestors through DNA testing. They just need to remember that, like more traditional genealogy research, genetic genealogy doesn’t provide the complete story of anyone’s ancestry. What it does provide is an insight into how complex our ancestry really is.
Resources
International Society of Genetic Genealogy. (n.d.). Genetic genealogy Q&A for beginners. Retrieved September 9, 2008, from the International Society of Genetic Genealogy Web site: www.isogg.org/.
About Us