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.
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.
Here’s a preliminary set of hypotheses, along with their scores (click to enlarge):
The following table shows why many of the 35 hypotheses can be excluded:
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.