DNA Sources, Information, and Evidence: Sorting it All Out
Sources play a vital role in genealogical research, and the quality and quantity of sources matter. Elizabeth Shown Mills, a renowned genealogical expert explains, “Sources give us information from which we select evidence for analysis. A sound conclusion may be considered proof.”
Part of the Research Like a Pro process is to “Dig out your papers and locate the sources on the FamilySearch Family Tree or other online trees that pertain to your ancestor. When you’ve gathered all the source documents, a thorough analysis of each and the information found within can clarify what you know and point you to your next avenue of research.”
After you test your DNA, you have an additional source that will help you in your family history research. In the context of using DNA in genealogical research, you are a source that gives information – in the form of DNA – that can be used as evidence to either support or not support a family relationship. DNA information must be used in combination with genealogical records and known family relationships; it is then used as evidence to give proof of relationships.
Types of Sources
There are 3 types of sources; original, derivative, and authored narratives. A person who takes a commercial DNA test is an original source – the highest quality of sources.
– You are a source.
– Your relatives are sources.
– People yet unknown to you are sources.
Types of Information
Information from sources is either primary (first-hand information), secondary (second-hand information) or undetermined.
Human original sources give primary information in the form of DNA test results. If you look at the actual raw data from your DNA test, you’ll see that it is comprised of the letters A, T, C, and G, which stand for the nucleotides Adenine, Thymine, Cytosine and Guanine.
Companies such as AncestryDNA, Family Tree DNA, MyHeritage, 23andMe, LivingDNA, and others compare your DNA information with DNA information from other people in their database. You are given a list of people with whom you share varying amounts of DNA. This “DNA match list” gives you a number in centimorgans (cM) or a percentage of the amount of DNA that you share with each person in your list.
Other sources: online family trees of your DNA matches
Other sources used in combination with DNA are the family trees of your DNA matches. Online family trees could be considered authored narratives. The person or people who built each tree made decisions about which information and documents to include to establish the identities of their ancestors. The information in the tree may be true, but you will still need to go through the tree to verify that the family information contained therein is correct. Over the course of your research, you may need to build trees for some of your matches.
Use sources and information to find common ancestors that link you to the people in your DNA match list.
You (a source) and your DNA (information) can be used as evidence to prove a relationship.
Remember that for DNA to be useful in genealogical research, it needs to be used in combination with known familial relationships. Sound genealogical research and records that corroborate relationships can then be validated by DNA.
DNA from a relative who is related on a specific line of a family may be used as evidence to help prove whether an historical person is your in-common biological ancestor or not. The more DNA information you have from relatives on a particular family line, the more evidence you have to prove an ancestral relationship.
Some general information to keep in mind:
atDNA: The larger the amount of shared autosomal DNA between you and a person on your match list = the closer the relative.
Y-DNA: Your test will name a Y-DNA Haplogroup and give a list of people who share the same or similar number of repeats of the genetic code in a marker location. The list may contain multiple people that have a very similar number of repeats at the same markers. The report will give a number indicating genetic distance. The smaller the genetic distance, the closer the relative, or the fewer amount of generations since the mutation or variance in the repeated genetic code occurred.
mtDNA or mitochondrial DNA is found in mitochondria, which are organelles in human cells that convert nutrients into energy. An mtDNA test yields an mtDNA Haplogroup. This DNA and the corresponding name of the Haplogroup are passed down from mothers to their children. Female children pass on the mtDNA to their children. An mtDNA Haplogroup can be used as evidence to prove that descendants are biologically related to their mother’s mother’s mother’s, mother and so on back in time. If two people share a mtDNA Haplogroup, they have a common female ancestor.
Analyze your sources
Now that you have DNA information, online family trees, and genealogical documents, you can test your relationship hypotheses through questioning the DNA data. I’ve found the best resource to date to find the probable relationships between you and your relative on your match list is the Shared cM Project 3.0 tool v4 at https://dnapainter.com/tools/sharedcmv4 Ask yourself, “Which of these matches verify the family relationships that I know? Do the cM and relationship probabilities match the relationships in the trees?” As you examine and analyze the DNA information, you will gain confidence in using DNA in this fashion.
Chart your DNA Matches
Because authored narratives in the form of family trees can quickly expand (and complicate!) the amount of information to investigate, it’s helpful to be able to efficiently analyze them. A good way to do this is to apply visualization techniques to the information you have. Draw a chart to visualize the people in your DNA match list and make sure they are placed correctly in your family tree. (See my previous post on how this can be done.) Seeing the Big Picture: 3 Ways to Chart Your DNA Matches This information can also be entered into your personal genealogy software. I love using Lucidchart.com because I can include just those relatives who will help me with my research objective, and I focus on the people who are on my DNA match lists and their direct ancestors.
As you draw your expanded chart, I recommend you include the following information:
1. Name of match – the name listed on the account, as well as the given name if you know it
2. Company the person tested with, and indicate if they are in Gedmatch.com
3. Relationship or relationship estimate if you are still figuring things out
4. Amount of DNA shared with you or the person you are helping
5. Other important information you feel is important
Next, color code the shapes— use one color to indicate the people on the DNA match list, a different color to indicate the common ancestors, and use another color to highlight the people you are looking for.
Finally, indicate the unknown or hypothesized relationships with a dotted line on your chart.
Continue to use Research Like a Pro techniques to confirm or disprove the relationships of the people in the dotted lines on your chart. After you confirm the relationships in one family line, repeat the process on other family lines to investigate and confirm relationships in your family tree. Soon you’ll know more than you ever did before as you Research Like a Pro with DNA!
 Elizabeth Shown Mills, “Fundamentals of Evidence Analysis,” Evidence Explained: Citing History Sources from Artifacts to Cyberspace, 3rd Edition, Revised, (Baltimore, MD : Genealogical Publishing Company, Inc., 2017), 15-38, particularly 24.
 Diana Elder, AG with Nicole Dyer, “Analyze Your Sources,” Research Like a Pro: A Genealogist’s Guide, (Highland, Utah : Family Locket Books, 2018), 19-29, particularly 19.