This blog is the result of two-year adventure in genetic genealogy. It began with a free, two-week trial of Ancestry and ended with multiple groups of triangulated autosomal DNA matches to provide the best available evidence to solve a 300-year-old mystery.
The earliest known ancestor of the SAINSBURY family of north Somerset was a Richard SAINSBURY. He was married in Portbury in 1745 but was not born in the area. So . . . where did he come from?
Over the years several researchers tried to solve this mystery. But the parish records of Portbury and surrounding parishes revealed no other SAINSBURY prior to 1745.
In December, 2018, I took advantage of a two-week vacation and free access to Ancestry to try my luck. First names often run in families, so I created a family tree for every branch of every Richard SAINSBURY I could find in 18th-century Somerset and neighbouring Wiltshire.
Along the way, I hoped some names from the tree of one of these Richard SAINSBURYs would re-appear in north Somerset records. Family members often migrate in groups, so perhaps Richard migrated to north Somerset with a cousin or two? But no such luck.
However, having built those family trees, I had a record of every documented Richard SAINSBURY born between 1700 and 1735 who might have been our ancestor. These became the “prime suspects” in this mystery.
But something other than traditional family history research would be needed to determine if any of these suspects were, in fact, our north Somerset ancestor.
Genetic genealogy works on the premise that distant cousins will sometimes share identical segments of DNA inherited from a common ancestor.
For example, if a descendant of Richard SAINSBURY of north Somerset shares an identical segment of DNA with a descendant of the brother or sister of any of the “prime suspects” discovered during that tree-building phase, it would indicate they are distant Sainsbury cousins.
More specifically, it would indicate that whichever Richard SAINSBURY is part of that group is our likely north Somerset ancestor. (See this blog’s About page.)
And so, in the spring of 2019, I began to work with SAINSBURY cousins and descendants around the world to see if our shared DNA could solve this mystery where traditional research had not.
Here’s how this genetic genealogy project proceeded:
- Establish a research question: Thanks to the guidance provided by Diahan Southard’s presentation at RootTech 2019 (Connecting your DNA Matches) the first step was to establish a research question. In this case: Where did Richard SAINSBURY of north Somerset come from? He is the first of his surname in the area. Prior to that, it’s been a genealogical brick wall.
- Data collection: Identify the early seventeenth-century places of origin of every SAINSBURY in every linked tree of every Ancestry user who shared DNA with a set of about 20 known SAINSBURY cousins. The early seventeenth century was chosen because that’s when our mystery ancestor would have been born. This phase involved much traditional research and tree-building. Each match was mapped as a new branch on a master tree.
- Identify geographic patterns: Use the geographic clusters that emerged from the date—in tandem with documentary evidence—to create a hypothesis for Richard SAINSBURY’s family and place of origin. In theory, this large pool of surname matches from a large set of known cousins was bound to contain a certain amount of “noise” (matches who happened to have a SAINSBURY in their trees, even though the genetic match is really on another line), but a preponderance of matches to our distant SAINSBURY cousins could (or likely would) outweigh the false positives.
- Look for any DNA triangulation groups: This phase of the project was guided by Debbie Parker Wayne’s 2016 article Triangulating Autosomal DNA. Finding groups of people with the same segment(s) of DNA—and an identifiable common ancestor—would support the theory developed in Step #3. Confirmation bias was a risk, but a “null” result would have prompted a re-think of the hypothetical ancestor and our mystery ancestor’s geographic point of origin developed in Step #3.
- Document DNA triangulation groups: Triangulation groups supported with good documentary evidence—and no other obvious explanation—are the best quality evidence to answer the research question using autosomal DNA. These were documented in blog posts.
- Maintain a record of all autosomal matches: All matches that support the answer to the research question are—on their own—additional evidence. But they could also form the basis of new triangulation groups. For example, singleton matches become “in common with” (ICW) matches when other known cousins share the same match. ICW matches become triangulation groups if those involved agree to upload to a chromosome browser site and their shared DNA is found to overlap with all others in the group.
With that brick wall removed, family historians of the SAINSBURY family of north Somerset can continue their research with the well-documented SAINSBURY family of Urchfont and Market Lavington, Wiltshire.