Clan Buchanan GEDMatch Project
- Bart Forbes
- 2 days ago
- 5 min read
(Thanks to Clan Buchanan Society International for the permission to reprint this article from the April 2025 edition of the Buchanan Banner.)
By Kim Tuovinen, CBSI Archaeologist, Residing in Wales and Australia; University lecturer and Professional Snuggler
Clann: Gaelic meaning ‘children of the family, offspring’, derived from Old Irish cland and previously Old Welsh plant from Latin plantation (‘offspring, shoot’).
One of the things that attracts a lot of people to engage with their Clan societies is the hope that they’ll be able to make more sense of their family trees. A fantastic example of a project that has been running for a number of years now is the Buchanan yDNA project hosted at FamilyTreeDNA and administered by Alex Buchanan and Ross Buchanan. This project has been able to demonstrate that the male-line descendants of the medieval Buchanan chiefs share a common ancestor with local Scottish clans, such as the MacGregors, dating approximately 1500 years ago. The project’s findings strongly suggest that the Clan Buchanan tradition of chiefly descent from Anselan O’Kyan from Ireland is most likely to be an Origin Myth, rather than historical fact. The project has also been able to group the key male Buchanan lines.
However, yDNA, which is passed down the male line on the 23rd chromosome, only tracks paternal ancestry: it is unable to show relationships between descendants along mixed male-female lines. For that, autosomal DNA is required.
Autosomal DNA refers to the genetic information contained in the remaining 22 chromosomes. These 22 chromosomes inherit genetic material from both parents, thus allowing relationships between distant grandparents, cousins, uncles and aunts, to be inferred along both paternal and maternal lines.
To that end, Clan Buchanan Society International is developing a DNA project focusing on autosomal DNA. This project complements the existing yDNA project. Its goal is to identify new relationships, and may eventually help participants to break through genealogical ‘brick walls’ - those ancestors whose backgrounds seem completely opaque to us due to lack of sources. Thus far, we have a total of 40 participating users. These 40 users have uploaded a total of 71 test kits, which already opens a door into some of the potential relationships between these 40 users.
As an example of how a member of the project can use the free tools provided by GEDMatch, I have used the ‘Segment Analysis’ tool to find out how closely related GEDMatch thinks my grandmother (for it is her kit that I’ve uploaded) is to the other project members.
How to use Segment Analysis:
Join GEDMatch and upload your raw data from a test kit from a DNA provider such as AncestryDNA, LivingDNA, 23andMe, FamilyTreeDNA and so on.
Navigate to Ancestor Projects > Search Projects and join CBSI’s Buchanan project.
Navigate to Ancestor Projects > Segment Analysis.
Enter your KIT NUMBER and set the parameters for your analysis:
Lower Segment cM Threshold: cM stands for ‘centimorgans’ the default is 7 because this most reliably identifies actual family matches. For more reliable results or to determine your closest matches amongst participants, set your Lower Segment cM Threshold to 7; note, though, that this tool can set a lower cM threshold as low as 1.
Upper cM Segment Threshold: the maximum available is 300, which is probably best to keep for your first segment analysis.
Lower Most Recent Common Ancestor (MRCA)/generations limit: you can leave this blank, as the default 1.0.
Selected Chromosome: leave blank for your first analysis.
Exclude Chromosome 23: leave this ticked for your first analysis.
Sort Options: click ‘Most Recent Common Ancestor’ for your first analysis.
Click ‘Submit’
You will then be taken to a results page which shows ‘how close’ your matches are to you (cM) on all chromosomes; the starting and ending positions of any matching segments of DNA, the cM distance on each chromosome, together with how much overlap exists between those matching segments. If you selected the sort option ‘Most Recent Common Ancestor’, the kits at the top of your search results should belong the person whom GEDMatch estimates most recently shares a common ancestor with you.
Future articles will explore how to make more extensive use of the tools available at GEDMatch in your own personal family history research, but I as an introduction I thought I would share some (anonymised!) results from my own Segment Analysis of my grandmother’s kit:
Number of kits tested against my Nanna: 70
Number of chromosomes in other participants’ kits with which my Nanna has a cM link of 7 or higher: 3
Number of chromosomes upon which my Nanna has a cM link of 6 or higher: 15 (34 including cM of 5.5 upwards.
The implication is that there is some level of relationship here between my Nanna and other CBSI DNA Project participants, but it’s a fairly long way back in time (and I have no way of knowing at this point whether these matches have been inherited from a Buchanan/Sept or from an alternative family line entirely).
At this point, I cannot be sure of exactly HOW my Nanna was related to these CBSI members (indeed, you can’t automatically assume any relatedness to Clan members, as relatedness can be along entirely different lines).
For now though, I have a pointer to potential relatives here, opening doors to better understanding my tree. We will continue to post hits and guides as the project progresses!
In conclusion, GEDMatch does represent a learning curve, but it’s one of the most accessible tools for drilling into autosomal. We would encourage as many people as possible to take a DNA test (one that includes autosomal DNA) as the greater the pool of datapoints, the more informative the project will become.
GEDMatch compatiblity
Remember that GEDMatch is compatible with data from ‘all major testing companies’, including: AncestryDNA, MyHeritage, 23andMe, LivingDNA, tellmeGen, and FamilyTreeDNA.
Note that 23andMe has recently filed for bankruptcy and the future of the business is currently uncertain. There is potential for a solution that will allow 23andMe to stay in business. If you have a 23andMe account, it’s recommended that you download your information from that site as soon as possible. For more information, click here
Centimorgans and Most Recent Common Ancestors (MRCAs)
A centimorgan (cM) is a unit of genetic linkage used in DNA testing to measure the distance
between genetic markers. It represents the likelihood of recombination occurring between
two points on a chromosome during meiosis. The higher the centimorgan value, the more
DNA is shared, indicating a closer genetic relationship. In ancestry and relationship testing,
higher cM values suggest a closer familial connection, while lower values indicate more
distant relatives.
Your MRCA is the most recent ancestor you share with the person to whom your DNA is
being tested. These are given in numbers of generations. Note that the numbers given will
be decimals (e.g. 4.76), so rounding up or down is recommended.
You can find out more about these genetic genealogy projects at:
Buchanan yDNA project: www.familytreedna.com/groups/buchanan/about
CBSI autosomal project: www.gedmatch.com (sign up and follow the link to ‘Ancestor Projects’ from your new home page. From there, click the ‘Search Projects’ tab and search for ‘Buchanan’).
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