Genetic genealogy is the use of Genealogical DNA tests such as DNA profiling and DNA testing. This is applied, in combination with traditional genealogical methods, to infer biological relationships between individuals. Genetic genealogy involves the use of genealogical DNA testing to determine the level and type of the genetic relationship between individuals.
As tests became more affordable, this particular application of genetics has been used extensively by family historians. The use of DNA tests has been extensively promoted by:
- surname study groups
- regional genealogical groups
- research projects such as the Genographic Project.
By late 2019, approximately 30 million people had been tested. As this field has developed, the aims of practitioners broadened, with many seeking knowledge of their ancestry beyond the recent centuries for which traditional pedigrees can be constructed.
Genetic genealogy gives genealogists a means to check or supplement their genealogy results with information obtained via DNA testing. In a family tree DNA review a positive test match with another individual may:
- Verify existing family tree research
- Establish that more than one surname variant is related
- Provide locations for further genealogical research
- Help determine the ancestral homeland
- Discover living relatives
- Validate or refute connections between families
- Validate or refute theories regarding ancestry
People who resist testing may cite one of the following concerns:
- Quality of testing
- Concerns over privacy issues
- Loss of ethnic identity
Finally, Y-DNA and mtDNA tests each only trace a single lineage (one’s father’s father’s father’s etc. lineage or one’s mother’s mother’s mother’s etc. lineage). At ten generations back, an individual has up to 1024 unique ancestors (fewer if ancestor cousins interbred) and a Y-DNA or mtDNA test is only studying one of those ancestors, as well as their descendants and siblings (same sexed siblings for Y-DNA or all siblings for mtDNA). However, most genealogists maintain contact with many cousins (1st, 2nd, 3rd, etc., with different surnames) whose Y-DNA and mtDNA are different, and thus can be encouraged to be tested to find additional ancestral DNA lineages.
Genealogical DNA testing first became available on a commercial basis in the year 2000 with the launch of Family Tree DNA and Oxford Ancestors. Since then other companies have been established, dozens of relevant academic papers have been published, and thousands of private test results organised by surname study groups have been made available on the internet.
The comparison of results may be complicated by the fact that some laboratories use different markers and report the results in different ways. By 2007 annual sales of genetic genealogy tests for all companies, including the laboratories that support them, were estimated to be in the region of US $60 million. By January 2013 it was estimated that around two and a half million people around the world had paid for a consumer genomics test, with the majority of participants testing for genealogical purposes.