How the X-Chromosome Solved a 100-Year-Old Adoption Mystery
We frequently receive requests from adoptees, foundlings, individuals with unknown paternity, and their descendants to assist in identifying biological ancestors. In a recent case we performed, we were able to use DNA test results to identify the biological parents of a client’s mother. Analysis of the X-chromosome held the key to determining the correct ancestral couple. Here we share their story. (In order to protect privacy, names have been changed.)
Lauren is the daughter of a woman named Mary Stoddard who was adopted in 1916 in Alabama. The organization that handled Mary’s adoption is no longer extant, and their records were destroyed in a fire. Additionally, our initial efforts to extend the client’s ancestry using traditional adoption methodologies were unfruitful, so we turned to DNA testing. The client subsequently performed DNA tests at several of the DNA testing companies.
We first took a step back and attempted to identify likely ancestors of the client’s mother. Lauren had several paternal relatives who had performed DNA testing, so we used their relationships to Lauren’s genetic cousins to eliminate paternal matches from our investigation.
Once we had identified likely maternal relatives, we estimated the nature of the relationships that the client had with her closest genetic cousins based on the number of centimorgans they shared in common. Centimorgans are a unit of measurement commonly used in genetics to specify how much DNA two individuals share in common. Up to the level of third cousins, relatives will share distinct and fairly predictable levels of DNA which can be used to estimate their relationship.
Next, we identified how the client’s genetic cousins were related to each other. When a test subject’s genetic cousins are also genetically related to one another, it can be extrapolated that their common ancestors are likely the source of their shared DNA with the test subject.
Finally, we incorporated the estimated relationships into documented genealogies to identify the client’s ancestors. Following these steps we were able to identify Mary’s grandparents, but we were still unable to determine the names of her parents. So far, we had only deduced that one was a child of Joe Jones and Laura Adams and the other was a child of Marion Smith and Alice Rogers.
The trees and shared cM values for her maternal great-grandparents and their descendants are shown in the accompanying diagrams.
Joe Jones and Laura Adams had five children: Martha, Charles, Joseph, Jennie, and Lula. We knew that Martha was not the mother of Mary since she was the ancestor of Match 1, and if she had been the mother, then Lauren and Match 1 would have shared much more DNA in common. We also suspected that it was not Lula since she would have only been 13 years old at the time of Mary’s conception. So that left us with three candidates: Charles, Joseph, and Jennie.
The other set of grandparents, Marion Smith and Alice Rogers, had ten children: Lou, Betty, Connor, Christopher, Edward, Vaughn, Frank, Alonzo, Philomena and Nancy. However, only the three oldest children, Lou, Betty, and Connor, were old enough to have been a parent of Mary. Even then, Connor was quite young, since he was only 15 at the time of Mary’s conception.
Through traditional genealogical research, we narrowed our search to just two possible couples who in 1915, at the time of Mary’s conception, were living in the same town in northern Alabama where Mary had been born. This led to the conclusion that either Mary was the daughter of Charles Jones and Betty Smith or she was the daughter of Lou Smith and Jennie Jones.
Next, we transferred the client’s test results to Gedmatch.com, a third-party site which allows analysis of shared segment data. Through one of the client’s X chromosome matches, we were able to determine the identity of Mary’s parents.
Lauren shared 48 cMs and a large segment on the X chromosome in common with Match 6. This X chromosome match also was a genetic cousin to Match 3 who was a descendant of Marion Smith and Alice Rogers. Through traditional research we determined that Match 3 and match 6 shared ancestry through their common ancestors Arnold Wood and Susan Sorenson – the maternal grandparents of Marion Smith.
The X-chromosome is the female sex chromosome. Males have one X chromosome that they inherit from their mother. Females have two X chromosomes: one that they inherit from their mother, and one that they inherit from their father. Like autosomal DNA, X chromosomes undergo a process called recombination which shuffles the DNA before it is passed on to the next generation. For the X chromosome, significant recombination can only occur when it is passed through a female. Therefore, for females, the paternally inherited X chromosome definitely comes from their paternal grandmother, as the X chromosome cannot be passed through two successive generations of males.
If Mary was the daughter of Lou Smith and Jennie Jones, then at any given site on Lauren’s maternal X-DNA there is a 25% chance that she inherited that DNA from Alice Rogers, a 12% chance that she inherited it from Julia Rockwood, and a 12% chance that she inherited if from Laura Adams. If this were the case, she could not have inherited any DNA from Celesta Wood since she would have been Mary’s father’s father’s mother.
If Mary was the daughter of Charles Jones and Betty Smith, then at any given site on Lauren’s X-DNA there is a 25% chance that she inherited the DNA from Laura Adams, a 12% chance that she inherited DNA from Celesta Wood and a 12% chance that she inherited DNA from Alice Rogers. She could not have inherited DNA from Julia Rockwood.
Since only one pairing of the candidates could explain the shared DNA on the X chromosome which came from Celesta Wood, we concluded that the parents of Mary Stoddard were Charles Jones and Betty Smith.
Using estimated relationships based on amounts of shared DNA, confirmed genetic relationships between cousins, documented family trees, and the X-chromosome, we successfully identified the parents of the client’s mother. This research also led to the discovery of five of Mary’s half-siblings and their children.
If you’re adopted or have an adopted family member, or would simply like to see what DNA analysis can do for your family tree, contact Legacy Tree Genealogists for a free consultation.