BackgroundAll living persons and test subjects have been anonymized for privacy reasons. In this particular study, AncestryDNA performed all DNA tests.
Preliminary Analysis
Preliminary Analysis
A cousin, CG from my Shaw line, received test results from AncestryDNA.
Basic clustering, via Ancestry’s “shared matches,” yielded a list of 34 member matches from the CG's paternal family line, the Shaw family.
Examination of these matches revealed that approximately one-third of these matches fell into one of two family groups, as indicated by the color coding of the table:
• members in blue were known individuals in the Shaw family tree; • members in magenta appeared to be members of a line with the surname M.
In addition, it should be noted that AS shares 36cM with AM.
M family member DM provided background information to facilitate organizing the M family matches into a pro forma tree, labeled below with the linkage each member shares with CG. The member matches from the M family are all descendants of ECM, born 1892.
Below, a similar chart for the Shaw family matches, as shown (also labeled as to DNA shared with CG):
In this case, the member matches from the Shaw family are all descendants of a Shaw/Mackintosh couple born around 1750. Because the common ancestor of the Shaw tree predates the common ancestor of the M tree, it makes sense to begin our detailed analysis by examining how the member of the M tree with the strongest linkage, JM, might be connected to the Shaw family tree.
Further AnalysisJM’s pedigree, as gathered from DM’s public member tree, shows several well-documented family lines. One line — JM’s paternal grandmother’s — contains a non-paternity event (NPE); there is also a maternal line ending in an unknown mother.
Determining how and where JM’s ancestry intersects with the Shaw family line depends to some extent on the localities of each family. In the case of the Shaw family, research shows this Shaw line consists of the descendants of three brothers (Angus, John and Duncan) Shaw, who immigrated to London, England from the vicinity of Inverness, Scotland around 1800. DS and CG are descended from John Shaw and his English wife Susanna Jones, and that line remained in London, England until 1913, when Farquhar Shaw and family moved to London, Ontario, Canada.
Looking over JM’s ancestors, we see that both of the births with unknown parents occurred in greater London — that of MAS in 1851, and EM in 1846. As such, we’ll begin our analysis by surveying two possible connections between JM and the Shaw line: JM to ECM to MAS (b. 1851) to a male Shaw — and/or JM to her mother, to her maternal grandmother to her maternal great-gandmother (b. 1846) to a female from the Shaw line.
In essence, we are looking for 3 generations between a male Shaw and JM or 4 generations between a female Shaw and JM such that the connecting individual on the Shaw tree was of childbearing age between 1846 and 1851. Since in each of our preliminary cases one parent is known to be an individual from outside the Shaw tree, JM’s connection to the Shaws would be that of a half, rather than full, sibling. Doing the MathAt this point, it may be helpful to discuss the implications of DNA linkage — the elephant in the genetic room these 11 Shaws and Ms share. The basic idea, of course is that the more DNA two individuals share, the more closely they are related. However, it’s worth remembering that determining such a relationship depends on two factors: the amount of shared linkage, and a certain degree of common sense.
Let’s begin with a basic example: an individual encounters a match on Ancestry that shares something like 3,500cM of DNA. Ancestry will tell you that this is a parent/child relationship, but amount of DNA linkage will not tell you whether the match is to your parent or your child. We can only infer the correct answer from the birth year of the match, as only one scenario at a time is realistically possible — despite either being valid based on the shared DNA.
Looking over JM’s ancestors, we see that both of the births with unknown parents occurred in greater London — that of MAS in 1851, and EM in 1846. As such, we’ll begin our analysis by surveying two possible connections between JM and the Shaw line: JM to ECM to MAS (b. 1851) to a male Shaw — and/or JM to her mother, to her maternal grandmother to her maternal great-gandmother (b. 1846) to a female from the Shaw line.
In essence, we are looking for 3 generations between a male Shaw and JM or 4 generations between a female Shaw and JM such that the connecting individual on the Shaw tree was of childbearing age between 1846 and 1851. Since in each of our preliminary cases one parent is known to be an individual from outside the Shaw tree, JM’s connection to the Shaws would be that of a half, rather than full, sibling. Doing the MathAt this point, it may be helpful to discuss the implications of DNA linkage — the elephant in the genetic room these 11 Shaws and Ms share. The basic idea, of course is that the more DNA two individuals share, the more closely they are related. However, it’s worth remembering that determining such a relationship depends on two factors: the amount of shared linkage, and a certain degree of common sense.
Let’s begin with a basic example: an individual encounters a match on Ancestry that shares something like 3,500cM of DNA. Ancestry will tell you that this is a parent/child relationship, but amount of DNA linkage will not tell you whether the match is to your parent or your child. We can only infer the correct answer from the birth year of the match, as only one scenario at a time is realistically possible — despite either being valid based on the shared DNA.
Of course this is all well a good for such an obvious example, but what about the 177cM JM shares with CG and the 120cM she shares with DS?
In this case, we can use the Shared cM Tool online at DNApainter.com to provide us with possible relationships. Entering 177cM into the tool we see the distribution in the image, which tells us that JM is most probably CG’s half-2nd cousin, but could be a 2nd cousin once removed, half-1st cousin twice removed, and so on.
OK, so, where do we go from here?
The solution lays with another tool at DNApainter.com: the tool used to generate the pro forma tree diagram, the What Are The Odds tool (WATO). Returning to our previous Shaw family diagram, we can clear out CG’s linkage, and enter in what we know JM shares with CG, DS, and BH.
The solution lays with another tool at DNApainter.com: the tool used to generate the pro forma tree diagram, the What Are The Odds tool (WATO). Returning to our previous Shaw family diagram, we can clear out CG’s linkage, and enter in what we know JM shares with CG, DS, and BH.
WATO allows us to place JM at various target points along the Shaw tree, and evaluate how well each target (called a hypothesis) satisfies the likelihood of JM’s shared linkage corresponding to that hypothetical position. WATO generates a probability score for each hypothesis so we can compare the possible to the less likely and to the impossible.
Here’s a preliminary set of hypotheses, along with their scores (click to enlarge):
Here’s a preliminary set of hypotheses, along with their scores (click to enlarge):
Each hypothesis represents a place where JM might be placed on the tree. Recall when we stated that valid connections depended not only upon linkage, but also a certain degree of common sense? This is one such instance, as the highest scores in the above diagram (Hypotheses 2 and 4) represent impossible conditions.
Bear in mind that we are looking for a half sibling connection with either: • 3 generations between a male Shaw and JM or • 4 generations between a female and JM and the connecting individual on the Shaw tree was of childbearing age around 1846 – 1851.
The following table shows why many of the 35 hypotheses can be excluded:
The following table shows why many of the 35 hypotheses can be excluded:
Removing the hypotheses excluded by the table leaves us with:
This suggests two possibilities: either John Shaw or his brother Duncan had a liaison with LS in 1850 that produced MAS a year later. The 10:1 probability indicates a 9.1% chance that Duncan was MAS's father, and a 90.9% chance that John was. Additionally, since we know from research that Duncan Shaw left London in 1847 for Malaga, Spain and only visited London periodically, the odds are skewed even further towards John Shaw.
With linkages relative to CG, our overview now becomes:
and so JM is indeed a half-2nd cousin to both CG and DS, which is consistent with the probabilities from the SharedcM Tool.
ConclusionThe preceding case study has determined that prior to his marriage in 1864, John Shaw (1811–1890) fathered a daughter, MAS, whose descendants populate the M family line.
ConclusionThe preceding case study has determined that prior to his marriage in 1864, John Shaw (1811–1890) fathered a daughter, MAS, whose descendants populate the M family line.
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