Many people who are unfamiliar with DNA will have a test conducted and then will believe the results are exact. Unfortunately, that isn’t always true, especially when it comes to the ethnic origins of their ancestors. Estimates of ethnic origins from DNA are ESTIMATES – or perhaps we should call them PROBABILITIES.
If your DNA test says you have 60% Irish ancestry, then we can assume that you undoubtedly do have a lot of Irish ancestry, but it probably isn’t exactly 60%. If your DNA test says you have 2% Middle Eastern ancestry, that means that you MIGHT have a little bit of Middle Eastern ancestry, but even that is not guaranteed. It could be more than 2% or it might be zero.
First of all, any DNA test that says you have a specific percentage of ancestry from another country is to be taken with some skepticism. For instance, your test results might say you have 60% Irish ancestry. While it is undoubtedly true that you do have a lot of Irish ancestry, the reported percentage will vary from one testing company to another. Even more confusing for newcomers to DNA is the fact that your brother’s or sister’s DNA test results might report a different percentage of Irish ancestry. Once you understand how DNA works, the reasons are obvious. However, it is confusing for newcomers.
In the case of siblings, both of your parents contributed to the family’s gene pool.
NOTE: I assuming both have the same father and mother. I am ignoring half-brothers and half-sisters. That’s a different topic.
You and your brother or sister each got SOME of your DNA from your father and SOME from your mother, but it is rare for both siblings to inherit exactly the same percentages from both parents. You never get exactly 50% from either parent. Instead, you might get 35% of your ethnic DNA from one parent and 65% from the other parent. Your sibling usually will receive different percentages of the same DNA. The percentages are variable but obviously always add up to 100%.
One common analogy is that DNA ethnic origins are like vegetable soup. The soup contains a mix of different vegetables. When you dipped your ladle into the soup bowl, you might have pulled out 25% potatoes, 35% carrots, and 40% beans. Your brother or sister then dipped their ladle into the same soup bowl and pulled out the same vegetables, but in a somewhat different percentage of each. To further complicate the picture, it’s also possible for one sibling to get no carrots! So, for example, your father might have a Viking ancestor whose DNA gets passed on to you but not to your sister.
Next, please keep in mind that all these numbers are ESTIMATES. A DNA test shows the percentage of various ethnic origins DNA you inherited from your parents, according to one laboratory’s test. If you take DNA tests from two or three or four DNA testing companies (as I have), you will find that even your own DNA ethnic origins will vary somewhat in percentages. That is because different testing companies are looking at different gene pools from different times in history. The human race has been migrating back and forth to different locations forever. Two thousand years ago, Europe was inhabited by often-roaming tribes of various barbarians. For instance, there were the Goths (including the Visigoths and Ostrogoths), Huns, Franks, Vandals, Saxons, Celts, and many others. They all roamed throughout Europe, settling down wherever they pleased as long as their new neighbors didn’t kick them out in various battles and raids.
So, if your DNA test says you have German ancestry, you need to consider the question, “Which Germans?” The same is true of Polish ancestry, Czech ancestry, and all other countries.
For instance, if your DNA test says you have a lot of Irish ancestry, the first question you need to ask yourself is, “In what years?” Was that the DNA of the Celts who were the primary inhabits of Ireland 3,000 years ago and whose own ancestors came from Germany and France and into the Balkans as far as Turkey, or was the testing company’s DNA database based on a mix of Celts and English and Normans who inhabited Ireland a few hundred years ago?
Here is another example: If your DNA test reports that you have English ancestry, the question you need to ask yourself is, “And where did THEY come from?” Almost everyone from England has a least a little bit of ancestry from Ireland, from the Nordic countries (primarily Norway, Sweden, and Denmark), and from Normandy, which is now a region of France. The ancestors of the Normans were mainly Danish and Norwegian Vikings (“Northmen”) in the 9th century, not the Franks from France. Of course, there was a mix of ethnicities in Normandy even in the 9th century; nothing is ever 100%.
Remember William the Conqueror? He and his army came from Normandy in 1066 and conquered England. Some soldiers of the occupying army took local wives or mistresses. Within a few years, the various bureaucrats, other “followers,” and even settlers from Normandy followed the army, again with many of them taking local women as their brides or mistresses.
Of course, most everyone knows what the Vikings were doing in England in the early Middle Ages, especially in the coastal areas of England. They were raping and pillaging in most all the villages along the coast and even traveling up navigable rivers. As a result, almost all English people of today have some Viking ancestry (primarily from present-day Norway, Sweden, and Denmark) as well as ancestors from other nationalities.
In addition, the boundaries of many countries have changed many times over the centuries. One common example involves Germany. If your DNA report says you have German ancestry, the question arises: “Which Germany?” In fact, Germany didn’t even exist as a country until 1871. Prior to that, the area now called Germany was a mix of small countries and city-states, and the borders amongst them changed frequently. There was Bavaria and Saxony and Prussia and Württemberg and a bunch of other countries and independent cities and more.
In addition, the ownership of Alsace-Lorraine has swapped between Germany and France several times. The people of Alsace-Lorraine typically spoke the Alsace-Lorraine dialect, which is similar to German but has a lot of French words and grammar rules. After the 30 Years War (1618 to 1648), many Swiss citizens migrated into Southwest Germany, including many who settled in Alsace-Lorraine, which was part of Germany at the time. In 1681, Strasbourg (the capitol city of Alsace-Lorraine) was conquered by French forces.
If your ancestor came from Alsace-Lorraine, was he or she German or French? In what years?
One of my ancestors came from the city of Strasbourg in Alsace-Lorraine, which was part of France at the time of his emigration to what is now Quebec Province, Canada in the late 1600s. In 1871, Alsace-Lorraine became part of Germany once again. In 1918, after Germany’s defeat in the First World War, the region was ceded back to France under the Treaty of Versailles. The region was then occupied once again by Germany during the Second World War. During that time, people from Alsace were made German citizens by decree from the Nazi government. After World War II ended, Alsace-Lorraine was transferred back to France, and all of its native-born citizens were decreed to be French citizens once again. However, the majority of citizens there still speak either German or the Alsace-Lorraine dialect that is similar to German but with a lot of French influence.
How about the DNA I inherited from my Alsace-Lorraine ancestor from the 1600s? Is it French or is it German DNA? Was he possibly of Swiss descent? What if his ancestors came from even someplace else before moving to Alsace-Lorraine?
Finally, the DNA testing companies are constantly updating and refining their databases of ethnic DNA. For instance, my mother’s ancestry is 100% French-Canadian, at least back until the 1600s. Yet one company’s DNA test result claimed that 50% of my DNA was from the Iberian Peninsula (Spain and Portugal). A few months later, the company updated its database with additional information. Now the same DNA company says that the one DNA sample I originally submitted now shows my maternal ancestry was mostly from France, which makes much more sense when you read the history of French-Canadians. There are dozens of similar stories as the various DNA testing companies keep refining their test procedures.
For the company that tested your DNA, do you know if they looked at the DNA of people from 200 years ago? Or 2,000 years ago? or even earlier? The different DNA testing companies use different data representing different points in time.
In short, your German or Irish or Polish ancestors undoubtedly all came from someplace else at some point in history. Indeed, you are the product of a large melting pot of various ethnic groups.
For more information, see: https://www.vox.com/science-and-health/2019/1/28/18194560/ancestry-dna-23-me-myheritage-science-explainer and https://www.vox.com/science-and-health/2019/1/28/18194560/ancestry-dna-23-me-myheritage-science-explainer.