Is DNA essential evidence for family historians?

Tonight I am participating in a panel discussion for the Society of Australian Genealogists about whether DNA is the 21st century tool for all family historians. I have been invited partly because of my experience using DNA in family history and partly because I specialise in the research process. I run the Society’s Family History Fundamentals course and I also lecture on a range of methodological topics such as research planning, proving your family history and source citations.

DNA is used by a lot of family historians. The question posed to me is, from a methodological viewpoint, should it be used by all family historians?

I first had my DNA tested with Family Tree DNA in 2017. At that time I was not fully aware of the potential that DNA had for my research, but I did have a question that I hoped it might answer. I had been researching my family history for over a decade but had still not been able to figure out who my paternal grandfather’s father was. His parents were unmarried and his father was not listed on his birth certificate. So I hoped that the results of DNA testing might provide some clues. When I received my results I realised that the process was not that simple. I had to learn how to analyse the results and incorporate them into my research. I also had to maximise the potential evidence from my DNA, so I tested with Ancestry DNA, uploaded to Gedmatch and MyHeritage, built up a large family tree on Ancestry and tested available family members.

When we research our family history, we are constructing a view of the past based on information that has been left behind. We obtain that information from sources. We interpret the information and use it as evidence to reach conclusions about the past. Traditional research primarily relies on documentary sources such as birth death and marriage records, but may also incorporate non-documentary sources such as oral history. DNA is another type of non-documentary source. Why might it be considered an essential source?

Our aim in family history is to make it as accurate as possible. If we do not, then we risk creating a family history that is not ours. Accuracy requires that our conclusions be reasonable and defensible. To achieve that we have to use the ‘best sources’ and conduct what is referred to as ‘a reasonably exhaustive search’. Can family history research be considered reasonably exhaustive if it has not utilised DNA evidence? To answer this we need to look at the power of DNA evidence.

Our family trees are based on establishing biological relationships between parents and their children. Documentary sources can provide evidence to support or refute these relationships, but it is rare that the strength of the support or refutation is definitive – usually, there is scope for further evidence to change the conclusion. However, DNA evidence is different. It can often provide definitive support or refutation, or at least something very close to definitive.

I have two examples in my own family history where the DNA evidence totally contradicts all the documentary evidence and in both cases I am convinced that the DNA evidence is correct.

The first is the identification of Gottlieb Malchow as the father of my great great grandmother Christina Malchow. Gottlieb was married to her mother, raised her and was listed as her father on her death certificate. Yet, the DNA evidence definitively refutes that he was her biological father. The DNA evidence also suggests who actually was her biological father. To me, it does not seem possible that there is another explanation for the evidence, so I think that I would argue that the evidence is also definitive about the identity of her biological father (though I am open to additional evidence to the contrary).

The second example where DNA has definitively disproven the documentary evidence is the discovery that my entire paternal line (except for my father) is not biological. Again, the DNA evidence is definitive. I have no DNA matches at all on that line and I do not match my cousin or uncle. It just is not possible for that line to be biological.

DNA evidence is also powerful evidence when the available documentary evidence is either lacking or is only circumstantial. The same great great grandmother I mentioned above, Christina, had six children. She was unmarried and her family were ashamed by her actions and the names of the fathers of her children were deliberately omitted from the records. The evidence that George Bassett was the father of her daughter, my great grandmother, was circumstantial – town rumour and the fact that one of his sisters brought up one of Christina’s other children. However, the DNA evidence is strong. Thirty DNA matches between myself and descendants of George’s siblings definitively support the conclusion that the father was from that family. A further match from a descendant of another child of George, together with the circumstantial evidence means that the conclusion that George was the father, while not definitive, is reasonable and defensible.

Extract of the summary of DNA matches to George’s family

So, DNA evidence can be essential in disproving documentary evidence and it can be essential where documentary evidence is insufficient. The final example of how DNA evidence is essential in family history is where there is no documentary evidence at all.

After discovering that my paternal line was not biological, I managed to identify my father’s biological mother by obtaining his adoption records. His mother was named in the records, but his father was not. It was only by analysing the DNA evidence that I was able to identify his biological father and use that information to build out my biological paternal line. While initially my conclusion about his identity was tentative, further analysis has built up a body of evidence that makes my conclusion reasonable and defensible.

When researching family history we are expected to use the best sources by conducting a reasonably exhaustive search. Without using evidence from DNA testing my family history would contain substantial inaccuracies and I would never have been able to build my paternal biological family tree. DNA evidence is therefore arguably the best source, when used in combination with documentary sources. I do believe DNA evidence is essential evidence for family historians.