How Accurate is Genetic Genealogy?
Don’t fall for the “scientific” label. It is not as accurate as you might think.
Lineage societies, such as The Jamestowne Society, are rejecting applicants citing DNA discrepancies with other lines. When an ancestor has more than one DNA line of descent, who is to judge which is the correct line? A lineage society? Remember, the DNA of the ancestor from 1608, is not being tested; the DNA being tested is from a person living today who claims descent from that ancestor.
Blind faith in Genetic Genealogy is no better than blind faith in the genealogy gedcoms that Internet genealogists download from Ancestry.com. Beware. I know from experience that administrators of individual family DNA projects, often manipulate the lineages they follow, rather than accept DNA results that differ from their expectations.
Genetic Genealogy became popular when science discovered that a man’s paternal lineage can be traced using the DNA on his Y chromosome (I-DNA). For those of European descent this is almost as though a man’s DNA came attached to his surname, which was passed on for generations from father to son. Theoretically, DNA profiling provides a genetic path that can track the surname through the generations. Because this applies only to males, women have been asking their male family members to be tested for them.
However, if DNA testing were truly a “scientific” Godsend for genealogists, would not the various laboratories performing this expensive testing come forth with the same DNA results? One cannot make data comparison between the various labs of the Genetic Genealogy industry, which casts serious doubts upon their reporting of “so-called” genetic matches. Researchers at the National Institute of Standards and Technology (NIST) recently published a paper recommending standards for genealogy testing labs to help improve their accuracy and reliability.
Genetic genealogy works by studying the sequences of repeating nucleotide (the base components of DNA) patterns on the Y chromosome known as short tandem repeats (STRs). Each STR is considered a separate marker for potential genetic matching because the number of times it is repeated will be the same for related males. For example, a person may have one STR sequence that repeats 12 times, another 11 times, a third 17 times and so on. If another male has a Y chromosome with a high percentage of the same STRs, it is considered likely that they share a common ancestor. Accurately counting the number of repeats is a tricky task and the source of much of the error in genetic genealogy tests, causing genealogists to make incorrect matches or miss family connections altogether.
In their paper, the NIST researchers explain the basis for the differing interpretations and recommend a solution using the agency’s certified reference material for human Y-chromosome DNA profiling (Standard Reference Material 2395), a collection of Y-STR markers that can serve as a means for genetic labs to calibrate their testing equipment. The researchers “strongly encourage [SRM 2395’s] use to enable compatible and calibrated measurements to be made between different Y-STR testing laboratories.” (NIST Guides Genetic Testing)
Until there is some sort of industry-wide standard for both buyers and sellers of these genetic genealogy services, they should be considered as just another tool in genealogical research and not the Holy Grail. For a lineage society or genealogist to proclaim that a descendancy of fourteen generations spanning 400 years is false because the DNA of some living persons does not match the DNA of other living persons is not logical nor scientific. Now that DNA testing for discovering the breed of one’s pet is becoming popular, at double the price of human testing, perhaps more science will be demanded. After all, there are stories of owners of expensive pedigreed animals learning through DNA testing, that their pet is not as pure-bred as they had paid for, if you believe the “scientific” DNA testing lab.
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