Richard Thornton | Apr 13, 2017 | 0
DNA Test Result ~ Tips
If you have chosen to get your personal DNA tested, here are some facts you should know so you will not be confused or disappointed by the results. DNA tests fall into three broad types, Y chromosome DNA, mitochondrial DNA, and autosomal DNA.
Y Chromosome: This chromosome is found only in males. It does not recombine with other chromosomes and so remains unchanged for generations. If you are a male, you have a virtually identical Y chromosome to your paternal great great grandfather and so on into the past. If you are female and you are interested in your paternal line, then you will need a close male relative to agree to submitting his DNA to learn of your common paternal ancestry.
The results can be misinterpreted by what I call the “surname effect.” If you are looking to confirm a specific ethnic ancestry, the Y-chromosome may create the impression that you have more ancestry of that group than you actually possess. For example, I knew a woman who was three-quarters German and one-quarter Italian, but she had an Italian surname because her paternal grandfather was Italian.
Likewise, there is a village in England where many men have a Y-dna from Africa, though they are average white Englishmen to all appearances. The explanation is that the Roman emperor Hadrian had a garrison of soldiers stationed permanently near Hadrian’s wall, to keep out the Celtic tribes to the north. These Roman soldiers came from all parts of the Empire, many from Africa, and they took local wives. Their descendants remained behind even after the western Roman empire collapsed. Almost two thousand years earlier, any other trace of African ancestry has long been diluted, but the Y-dna remains strong, almost as if those black African soldiers were stationed there only fifty years ago. The local women show no trace of the African Y-dna, but their fathers and brothers do.
Mitochondrial DNA: Mitochoondria are organelles that process energy in the interior of all of our cells. They have their own DNA that never merges with the “nuclear DNA” of the cell. Mitochondrial DNA, or mtDNA, governs only the operation of the mitochondria, and not other bodily traits, such as appearance.
MtDNA is passed only from a mother to her children, with few mutations, over thousands of generations. Everyone, male and female, has the same mtDNA as his or her mother, no exceptions. Even the heavy-duty mitochondria on each man’s sperm cell have the same mtDNA has his mom, but these are not passed onto his children.
For example, as a male I have the same mtDNA as my maternal grandmother’s first cousins (we are descended from sisters) but different mtDNA from my own children. Because mtDNA does not dilute over time, it may not reflect large amounts of ethnic mixture that have occurred recently.
Autosomal DNA: This is a sampling of all of your 46 chromosomes. The laboratory compares your samples to all the samples in their database, which grows larger with each individual tested (including you). Where your DNA profile most closely matches some other sample populations, then it can be deduced that you have common ancestry with that population.
Here is where it gets tricky. The best DNA samples come from living populations, though scientists now have the ability to sample DNA from mummies and other humans now dead for centuries. (Also, sometimes large populations move about. There are some regions of the world where most people are descended from immigrants, and others where most people have lived in the same place for thousands of years. Some DNA testing companies take this into account)
For example, many south Asians (India, Pakistan, Bangledesh) have a genetic marker that originated in central Asia, and this same marker is also found in North American among Native Americans. This does not mean the South Asians are ancestors of the Native Americans, or vice versa. What happened is that during the Ice Age, some central Asians, crossed Siberia and entered North America. Millenia later, central Asian nomads, the Mughals, invaded India and spread their DNA around India, as conquerors are wont to do. The South Asians and Native Americans with the DNA matches are like cousins who share the same grandparents.
The above example illustrates how DNA results have to be interpreted through the lens of other fields of knowledge, like history. You must also consider that certain factors may give you different DNA results than you expected. For example, adoptions were frequently concealed even from the adoptee, who may not have learned until adulthood that they were adopted.
Stepfather adoptions are still common. Both US Presidents Gerald Ford and Bill Clinton carry their stepfather’s last names, and they shared that surname with their wives and children. It is not even a family secret that those names are not inherited from biological ancestors, the names Ford and Clinton are how the descendants willingly choose to identify themselves, and those are now the real family names.
Likewise, those adopted into Indian tribes often maintained a strong identification with their adopted tribe, even when they had been adopted when old enough to remember their life before adoption. The power of culture and the experience of upbringing will often carry more weight than biological inheritance. So you have to filter DNA test results through your own personal knowledge of family history and even local history. Some DNA testing companies, such as DNA Tribes, actually state that you have to consider oral and documented history in order to make sense of DNA test results.
It is also useful to consider the local history of the places where you and/or your ancestors are from. Learn which Indian Nations once lived there, which ethnic and religious groups later settled there, and even which industries once dominated a region, all of which may provide clues as to what kinds of people have lived, or passed through, the places where your ancestors have lived.
For me, DNA testing confirmed our family oral testimony, and the oral history of the Creek Indians. It even provided hints to our seemingly inherent nomadism even in 20th century America, which DNA tests hints as coming from the nomadic tribes of Africa. DNA testing is an exciting part of the adventure of genealogy.
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Kevin A. Thompson
Kevin Thompson is of Creek descent and raised in the Southern Tier region of New York State. He has a Masters in Teaching, and currently employed in the social work field. He is also a US Army veteran.