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Thursday, 5 May 2022

Finding the Forrest family - using chromosome analysis

A DNA match alone doesn't prove a relationship to a particular ancestral couple, but they can provide further evidence to support a theory. In this case, a collection of DNA matches who also shared the same segment of DNA helped to identify further children of the ancestral couple and provided further evidence to confirm their relationships. 

This is my mum's chromosome map - what is a chromosome map and how did some of this information help me find the Forrest family? 

Mum's Chromosome Map from DNA Painter

Chromosome mapping is a technique used in genetic genealogy using autosomal DNA results. The goal is to identify which ancestors were the source of various segments of your DNA.  Once you discover how you’re related to someone, you can figure out which ancestor is likely to have been the source the DNA you share with them. It's an ongoing process and to date, I've mapped or assigned about 46% of mum's genome to known ancestors. It's just like a jigsaw puzzle! Each colour represents confirmed DNA matches to specific ancestral couple. 

Legend - Mum's Chromosome Map

Below is the pedigree chart for my maternal grandmother, Helen Forrest McDougall, using the Ancestral Trees tool from the DNA Painter site. I’ve also used the DNA Filters feature to indicate those ancestors that I’ve been able to confirm through DNA analysis. 

Pedigree Chart for Helen Forrest McDougall showing DNA confirmed ancestors

Prior to DNA testing I had been unable to research beyond my grandmother's great grandmother and namesake, Helena Annie Forrest, but I've recently identified over 25 matches back to Helena’s parents - my 4 x great grandparents, David Forrest and Margaret Anderson and a further 12 matches back through Margaret’s parents, James Anderson and Cockburn Smith. 

Helena married Alexander Dougal (later McDougall), a weaver,  in Girvan, Ayrshire, Scotland in 1835. She can’t be identified on the 1841 census, but is on the 1851 census in Girvan with her husband and children. The census indicated that she was born about 1819 in Edinburgh. Her son, George, my 2 x great grandfather, was born in 1855 and his birth certificate also states that his mother was born in Edinburgh. Unfortunately, while Helena is listed on all the later census, they indicate that she was born in Girvan, which was not helpful!

Death Certificate - Eleanor Annie McDougall - 16 October 1886

Helena's death certificate in 1886 provided details of her parents, David Forrest, a shoemaker and Margaret Anderson, and confirmed that they were both deceased. 

I tested my mum at Ancestry in 2018 and also have access to two of my aunts kits. Their Ancestry results have since been uploaded to other sites including MyHeritage, Family Tree DNA (FTDNA) and Gedmatch. This provides access to their segment data, which is required to undertake chromosome analysis, and also identifies matches who may have tested and/or uploaded to the other sites. I’ve confirmed DNA matches back to Helena and her husband Alexander through 3 of their children at Ancestry and more recently at 23andMe where I have also tested mum. 

Confirmed DNA matches back to Helena Forrest and Alexander McDougall

No baptism for Helena can be found in the Old Parish Registers, but I have located baptisms for five children born to a David Forrest and Margaret Anderson between 1800 and 1807 in Livingston, Midlothian, which is about 25 km west of Edinburgh. There is a gap between the last recorded baptism for David in 1807 and Helena’s possible birth, but could they also be her parents?  

Baptisms at Scotlands People for children of David Forrest and Margaret Anderson

I decided to add the family to my Ancestry tree, also adding the Research Status tree tags Hypothesis and Unverified to warn anyone else that they were still speculative.

Using Tree Tags at Ancestry 

ThruLines™ is an Ancestry feature that groups your DNA matches under potential common ancestors, so I was excited to see soon updating my tree, that ThruLines™ had generated a couple of potential matches, through a son named Peter Forrest. 

ThruLines™ showing potential DNA matches through descendants of David Forrest 

Like my ancestor, Helena, there was no baptism record for Peter either, however, census records indicated he was born about 1817 in Blackburn which is also near Livingston in Midlothian. His death certificate gave his parents as David Forrest, a master shoemaker and Margaret Anderson, so could he be another child of this same couple? 

Peter and his wife, Isabella Wilkie had 9 children and we now had DNA matches through three of those lines.  As a result, I added Peter and his children to my tree using the Hypothesis and Unverified tree tags while I continued searching and gathered more evidence.

Fast forward a few months and I received a message from Cathy in Canada, a 3rd cousin DNA match, who I’d contacted a few years earlier, asking me how confident I was that David Forrest and Margaret Anderson were Helena’s parents. 

I was reasonably confident as mum and her sisters shared many of the same matches with Peter’s descendants, which had provided us with tree triangulation and the family names also supported the connection. However, given the matches were beyond 3rd cousins, we really needed to be able to compare segment data. 

Although Cathy and mum shared 29 centimorgans (cM) at Ancestry - they had no shared matches, other than myself and one of my aunts. Although they both matched Cathy, neither of my aunts had any additional shared matches with Cathy either, so I was curious to know if Cathy matched with any of Peter Forrest descendants, or the matches from 23andMe. 

Mum's match with Cathy in Canada and their shared matches
Sharing preferences 

Cathy agreed to share her match list with me as a collaborator as I had offered to start grouping her matches for her. Cathy had also uploaded to MyHeritage where she and mum shared 42 centimorgans, which was consistent with Ancestry’s unweighted results.  

Comparison of Mum and Cathy's matches grouped into the McDougall and Forrest lines

Once I had access to Cathy’s match list I was able to confirm that she too shared several of the matches from the Peter Forrest line. As these were mostly below 20 centimorgans, they had not appeared in the shared match tab for any of Ancestry kits I had access to.   

I could also see we shared many other potential matches and added them to our groups for further analysis. 

I continued to build out my tree and Ancestry’s ThruLines™ updated again, identifying more matches through another two possible children of David and Margaret - Margaret and Jessie. 

ThruLines™ showing suggested matches through descendants of Margaret Anderson

Once again, no baptism records for Margaret or Jessie could be found, however both gave their father’s name as David Forrest, a cordwainer or shoemaker at the time of their marriages, and their parents were recorded as David Forrest and Margaret Anderson at their deaths, so I'm confident they are all descended from the same couple. 

Analysis of Cathy’s shared matches with mum and her sisters at MyHeritage revealed that some of the Ancestry matches had also tested or uploaded to MyHeritage. I was able to compare the shared segments for these matches and confirmed that they triangulated - meaning they shared some of the same segments.  MyHeritage add a symbol to the right of the match indicating they share triangulated segments. 

Mum's match with John at My Heritage showing triangulated matches with David and Robina

Some of these new matches, like David and Robina, take us back yet another generation, to Margaret’s parents - James Anderson and Cockburn Smith, and are descendants of Margaret’s sister, Susan.

Comparison of kits at Gedmatch between Mum, John, David and Alan 

David and John were good bridging matches between the sites, as they had also uploaded to Gedmatch, where I was able to compare the various kits with each other. 

Both David and Robina also shared their Ancestry results with me as well, which was helpful in confirming where many of the other shared matches connected in our trees. 

Mum also had known matches at 23andMe that I had already identified and painted into mum’s chromosome map. 

Mum's known matches back to Helena Forrest and Alexander McDougall from 23andMe

The chromosome map at DNA Painter allowed me to paint our shared segments from all of the sites and visually compare the overlapping segments. Below is a snapshot showing all available segment data between each of the matches with mum and her sisters back to their most recent common ancestral couple. 

Mum's chromosome map showing matches back to the McDougal/Forrest/Anderson/Smith lines

I have zoomed in on those chromosomes where we have triangulated segments. Primarily Chromosomes 4, 6 and 7.

Chromosome Map focus on David's shared segments

You may see slightly different results for the same match at different testing sites as they do test at different locations. For example, David has uploaded his Ancestry results to both MyHeritage and Gedmatch. Gedmatch reports that he shares two small segments on chromosome 4, while My Heritage uses imputation to add to the results of people who upload results from different vendors, and in this case appear to have joined these segments together.

Chromosome Map - Chromosome 4

In relation to the shared segments on Chromosome 4, you can see that I have currently mapped them to the three sets of Common Ancestors, based on the relationship of the match to mum:

  • Graeme, a 3rd cousin, once removed (3C1R), is mapped to the 2 x great grandparents, Alexander Dougall and Helena Forrest 
  • John, a 4th cousin, is mapped to the 3 x great grandparents, James Forrest and Margaret Anderson 
  • Alan, David and Robina, all 5th cousins, are mapped to the 4 x great grandparents, James Anderson and Cockburn Smith 

However, all these segments can actually be attributed and painted to the 4 x great grandparents, James Anderson and Cockburn Smith.

Chromosome Map - Chromosome 6

While, Chromosome 6 can be attributed to the 3 x great grandparents, James Forrest and Margret Anderson. 

I have also asked Robina if she would consider uploading to Gedmatch, as I am sure my mum shares this segment with her and that there is an anomaly at MyHeritage, as Robina shares this segment with my aunt, my sister and my niece. 

Thrulines™ showing suggested matches through descendants of James Anderson

Through collaboration with David and Robina and sharing our Ancestry results with each other we've now also been able to build and confirm our trees back further. Mum's Thrulines™ has identified a further 9 matches back to the next generation - James Anderson and Cockburn Smith, through their daughters, Susan and Isobel. 

While Thrulines™  are great for providing hints as to how we connect with some of our matches, I use a spreadsheet for tracking all our known matches and also use a programme called GDAT (Genealogical DNA Analysis Tool) to analyse matches further. 

The What Are The Odds tool (WATO) at DNA Painter a simple way of visualising matches across the different platforms and it’s also an easy way to share information with others working on the same families. I'm also now adding a link to the WATO tree to the profiles for the Common Ancestors in my Ancestry tree.  

WATO tool used to track confirmed matches

I would love for more of our shared matches to upload to sites with a chromosome browser. I know we have inherited additional DNA through other segments from these couples. My Auntie Irene doesn’t share these segments on Chromosome 4 or 6 with any of these matches that I've used in this analysis, but she is a match with several other matches on these lines at Ancestry - so it must be on a different chromosome/s! 

Many thanks to Cathy, David, Anne, Robina and Nicolette for sharing their Ancestry results with me.

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