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Posted by on 15 March 2013
Debbie Kennett is a freelance editor and genealogist. She is the author of The Surnames Handbook (History Press, 2012) and DNA and Social Networking (History Press, 2011).
The announcement of the publication of Sense About Science’s new briefing on Sense About Genetic Ancestry Testing attracted substantial media coverage. However, some of the articles did not give the wider context which may have given the false impression that all DNA ancestry tests are "meaningless". This left some readers to wonder about the scientific credibility of the DNA testing used in the investigation of the presumed remains of Richard III or the tests taken by genealogists as part of their family history research. However, the briefing made it clear that "There are credible ways to use the genetic data from mtDNA or Y chromosomes in individual ancestry testing, such as to supplement independent, historical studies of genealogy." This combination of genealogical research with DNA testing is known as genetic genealogy, and is a more specific and rigorous application than the generalised “deep” ancestry tests critiqued in Sense About Genetic Ancestry Testing.
There are three different types of DNA tests that are applicable for family history purposes. Y-chromosome DNA tests explore the direct paternal line and are typically interpreted within the context of a surname study.1 Mitochondrial DNA tests can be used for genealogical matching purposes on the direct maternal line. Autosomal DNA tests, which currently sequence up to one million markers, can be taken to find genetic matches with close relatives, and sometimes more distant cousins, on all the different lines, through both males and females. Good genealogy research examines and assesses all available sources, and DNA testing is just one type of record that can be weighed up with all the other evidence before drawing any conclusions.
Such is the popularity of genealogical DNA testing that the largest collections of mtDNA sequences and Y-chromosome haplotypes are available not in scientific databases but in genetic genealogy databases.2 Deep-rooted pedigrees compiled by genealogists can be consulted to inform the interpretation of research findings from population genetics studies, and there is considerable scope for further collaboration between genetic genealogists and population geneticists.3
A single DNA test on its own provides only a limited amount of information, and the greater value of a test lies in the comparison process. This has led to the growth of large genetic genealogy databases and a proliferation of volunteer-run DNA projects, many of which are studying surnames. Y-chromosome DNA testing can be used to establish whether or not two men with the same surname share a common ancestor within a genealogical timeframe. Y-DNA testing can also help to confirm relationships deduced from traditional genealogical research and to establish which variant spellings of a surname are related. Many such studies are being carried out by members of the Guild of One-Name Studies. Mitochondrial DNA tests can be taken to compare relationships on the direct maternal line. MtDNA testing was used in the case of Richard III, and the preliminary results provided strong support for the identity of the remains found in the Leicester car park. The DNA evidence alone does not prove the case, as many press reports suggested; it supports other evidence, and further DNA analysis is ongoing.4
An autosomal DNA test can be taken to verify whether or not two people share the expected amount of DNA for the presumed relationship, and can be used, for example, to confirm that two people share the same grandfather or great-grandmother.5 DNA tests do not confirm specific relationships but instead rely on probabilities to estimate the likely range within which a common ancestor might have lived or, in the case of autosomal DNA tests, the degree of kinship between two people. The more markers that are compared the more secure the verification.
While most people wishing to research their family tree would in the first instance be best advised to "dig around in their loft" before purchasing a DNA test, for some people, such as adoptees, this is not an option. For males a Y-chromosome DNA test can provide clues to the person's biological surname.6 7 A growing number of adoptees, both male and female, are finding matches with close family members in the large commercial autosomal databases.8 9 10
While the inferences drawn from deep ancestry DNA tests may sometimes be speculative or so generalised as to be meaningless, genealogical DNA tests can be used effectively and legitimately as an additional tool in family history research.
1 King TE & Jobling MA What’s in a name? Y chromosomes, surnames and the genetic genealogy revolution. Trends in Genetics 2009 25;351-360.
2 Congiu A, Anagnostou P, Milia N et al Online databases for mtDNA and Y chromosome polymorphisms in human populations. Journal of Anthropological Sciences 2012 90;1-15
3 Larmuseau MHD, Van Geystelen A, van Oven M, and Decorte R Genetic genealogy comes of age: perspectives on the use of deep-rooted pedigrees in human population genetics. American Journal of Physical Anthropology 2013 Feb 26 [Epub ahead of print]
4 Details of the genealogical research and DNA testing used in the case of Richard III can be found on the University of Leicester’s website. The detailed research will be submitted for publication to a scientific peer-reviewed journal when the ancient DNA analysis has been completed. See also John Ashdown-Hill, The Last Days of Richard III and the Fate of his DNA, The History Press, 2013 edition.
5 Huff CD, Witherspoon DJ, Simonson TS et al Maximum-likelihood estimation of recent shared ancestry (ERSA). Genome Research 2011 21:768-74
6 Rincon P Adoptees use DNA to find surnames BBC News online, 18 June 2008
7 War baby searches for father ABC News, 5 October 2012
8 Finding family Case history published on 23andMe blog
9 23andMe's tools help solve ancestry mystery 23andMe blog
10 CeCe Moore Adoptee reunites with birth family at 23andMe Your Genetic Genealogist, 21 December 2011