Triangulation at 23andMe

A Segment-ology TIDBIT

23andMe has a great feature. It starts out as a standard In Common With (ICW) list for each Match you are sharing with (old Shared Genomes Matches and new Open Sharing Matches). This ICW list is near the bottom of your Match’s page. But the difference with other ICW lists is the Shared DNA column. The Matches marked with a “Yes” have overlapping segments – and over 99% of the time they form a Triangulated Group (TG).

So go to your DNA Relatives page and scroll to the bottom and click on the “Download aggregate data” link. You’ll get a spreadsheet of all your matches and most of the 23andMe data. Sort the spreadsheet, and delete the ones with no segment data. Then sort on Chromosome Number and Chromosome Start to put them in a particular order. Add a column called “TG ID”. Now you’re all set to begin Triangulating.

Start with the first Match in the spreadsheet (let’s call it A). Click on the hyperlink* that takes you to A’s page, scroll down to the ICW list and note in your spreadsheet Match A and each Match with a “Yes”. Since you are starting on Chr 01, call this TG: 01A, and put 01A in the TG ID column for A and each “Yes” Match. This pretty much identifies all the other 23andMe Matches that are in a TG with (A). The whole TG 01A (of 23andMe Matches) is created through one Match! There may be a few that don’t overlap A enough to form a shared segment at 23andMe, but all you have to do is go down your spreadsheet list of 23andMe Matches and select the next Match (B) that is not already in a TG; click on B’s hyperlink and look at their ICW list for “Yes” Matches with (B) – some will either overlap with (A) (call all of them 01A, too); or they all form a new TG (say 01B) – one or the other. Then continue with the next Match not already in a TG.

One could probably go through their entire 23andMe list of shared Matches in a few hours, creating TGs for all of them. There may be some with no ICW “Yes” Matches – give them their own TG; and move on. Be careful with Matches with more than one shared segment – make sure to treat each segment individually – this may take a little extra analysis.

Remember, TGs represent segments (from an ancestor) on one of your chromosomes. They are equivalent to phased data. I consider all shared segments at 23andMe which Triangulate to be IBD. All of them should be in a TG on one side (parent), or the other.

If you have known relatives in any of the TGs you can assign those TGs as Paternal or Maternal. This often allows other, overlapping TGs to also be assigned to a side, using logic.

*Note1: clicking on the 23andMe hyperlink (Link to Compare View) is a little tricky – I usually just copy (Cntr-C) the spreadsheet URL, and paste (Cntr-V) it into the URL bar of any open 23andMe page – hit Enter. It goes pretty fast.

Note2: feel free to use any TG ID numbering system you want. I think it’s wise to start with the Chromosome number. But you can name your TGs Bill, or Bob, or Sue if you want. You are creating groups that will tie to ancestral lines.

ARE YOU READING THIS FTDNA? ALL YOU NEED TO ADD IS A YES!! And AncestryDNA could add a similar feature, and hell might freeze over, too.

Enjoy easy Triangulation at 23andMe…


[22M] Segment-ology: Triangulation at 23andMe TIDBIT; by Jim Bartlett 20170720

Using a Child to Determine the Side

A Segment-ology TIDBIT

Normally your child’s atDNA cannot indicate which side of your DNA a Match is on. But, a child only gets one side of your DNA at a time. In other words: you have DNA from both of your parents that covers each of your chromosomes from beginning to end; but you can only pass on one side to a child. Your parents are your child’s grandparents – every bit of your DNA passed to a child is either one of the child’s grandparents (your parents) or the other. Please review Bottom-Up and Crossovers to see the approximate 34 crossover points that divide all of your child’s DNA into about 57 segments from your parents. This is a very important concept in atDNA, and well worth the time to study it until you understand it.

So if you have a segment that you cannot figure out which side it’s on (your maternal or paternal side), having a child also match on that segment doesn’t give you any insight. Because: if you don’t know which side it’s on for you, you don’t know which grandparent it’s on for your child.

However, if you have tested at multiple companies, a child may help. Here is an example.

At 23andMe I have 3 Matches who all match me and each other on the same segment – a Triangulated Group (TG). There are no other 23andMe Matches, or any known cousins, who overlap this segment at 23andMe. However at GEDmatch I have a number of Matches with overlapping segments, and I’ve formed two TGs. And with my Dad’s kit at GEDmatch, I know which TG is paternal and which is maternal. I also have a child at GEDmatch, and he matches the maternal TG, but not the paternal TG. So my son got my maternal DNA for this segment. This son was also tested at 23andMe, so checking the ICW list with the 3 Matches above, they all include my son with a “Yes” – meaning an overlapping segment. So I can conclude that the 3 Matches at 23andMe form a maternal TG for me, because my son only got my mother’s DNA on this segment.

This now lets me communicate this information to each of the 3 Matches: our Common Ancestor will be on my mother’s side (and I include a list of Patriarchs of those lines in my message). I’ve made up two standard messages for 23andMe Matches – one for each side – which I can quickly copy and paste into the 23andMe message box. I initially get about 10-20% response – usually with a thank you for providing a concise, and easy to review list of potential Common Ancestors. Over time, additional responses trickle in. It’s a quick and easy way to find those Matches you can work with. And sometimes these “seeds” bear fruit months and even years later.


[22L] Segment-ology: Using a Child to Determine the Side TIDBIT; by Jim Bartlett 20170712


Amount of DNA vs Number of Matches

A Segment-ology TIDBIT

There are two concepts at work here – each is different – keep them straight and separate. Each in it’s own way can provide insights.

1. Amount of DNA from Ancestors. Although DNA from your Ancestors is random, there is some uniformity. You get exactly 1/2 of your atDNA from each parent; pretty close to 1/4 from each grandparent; about 1/8 from each great grandparent. By the time you get to your 128 5G grandparents, the average will be 1/128 from each one of them (roughly 1 percent), but with each generation past your parents, the deviation from the average increases. Still – the total of all ancestors at any generation will sum to 100 percent. On average you got about 15cM from each 5G grandparent, which may be in one segment or spread over several segments. The companies report that, in general, you will not share enough DNA to match most of your 6th cousins; but we know that you have so many 6th cousins that you will share with many of them – experience shows you will share from 0-21cM with some your 6th cousins. [see The Shared cM Project 2.0 at ]

2.Number of Matches from Ancestors. This depends on several factors: Number of cousins, who tests, endogamy, etc.

A. The number of cousins you have from each Ancestor is directly related to the size of their families leading to the number of their living descendants. Larger families => more cousins => more Matches.

B. Similarly the number of cousins you have from each Ancestor is directly related to how far back that Ancestor is. Distant Ancestors => more cousins => more Matches.

C. Who tests. This may be most pronounced with recent immigration. The more recent an Ancestor immigrates, the fewer number of living descendants in the US, where the highest percentage of atDNA test takers live. Recent immigration => fewer cousins tested => fewer Matches.

D. Endogamy. With endogamy, the amount of shared DNA increases, resulting in many more Matches who otherwise might not have matched. The classic case is Ashkenazi Jews, who tend to get many times the number of Matches others get, and the Matches are in fact somewhat more distant than indicated. This also applies to other endogamous populations. Endogamy => more cousins => more Matches.

Some of my experience and observations

My maternal grandmother was from immigrants to US in 1850s. Roughly 1/4 of my atDNA is from her, and 1/4 of my Chromosome Map has TGs from her line. But, I get relatively few Matches on this 1/4 of my Ancestry, and some of the “gaps” in my Map have no Matches in them at all. When I get only 1 or 2 Matches in a TG on my maternal side, it’s pretty certain they are from my grandmother’s line. The other maternal TGs are from my mother’s paternal side with deep Colonial Virginia roots – they tend to have many Matches.

As the Matches pour in, and are added to my TGs and Chromosome Map, I can see where some TGs have many Matches and must come from distant Ancestors – perhaps at the limits of my Tree, or beyond – so I focus on the closer MRCAs (Most Recent Common Ancestors) which provide pointers. In some cases I’ve found the Ancestor had a Plantation and raised many children.

Some of the other TGs have small to medium numbers of Matches, and where I can find an MRCA, they tend to be smaller Colonial families – folks who moved around a lot; died earlier in life; and/or had few known children who survived.

So as you form TGs, and look at the resulting Chromosome Map, they start to paint a picture…


[22K] Segment-ology: Amount of DNA vs Number of Matches TIDBIT; by Jim Bartlett 20170517

Format for AncestryDNA Notes

A Segment-ology TIDBIT

Here is an example of the format I usually use for AncestryDNA Notes, line by line:

[1] 6C1R: BUTCHER/BUSH > Valentine

[2] Gm 123456 [03F25] 15.1cM

[3] 12.4cM/1Seg

[4] SM: 6 [1 is 4C on BUTCHER]

[5] m5/4/17; mr5/5/17w/Gm#

[6] Added to xls & Notes

[1] is just line number, you don’t need to type that in

6C1R is 6th cousin once removed; 4Cx2 is double 4C

BUTCHER/BUSH is our MRCA surnames > Valentine is the child my Match descends from

Gm is GEDmatch ID

[03F25] is my Triangulated Group ID [Chr 3; F means start in 50-60Mbp range; 25 are first two Ahnentafel numbers of my ancestry to the MRCA – in this case my father and his mother]

15.1cM is cM per GEDmatch

12.4cM is cM per AncestryDNA [almost always smaller]

SM = Shared Matches; then the number of them; then any key info about any of them [in brackets]

M5/4/17 means I posted a message; mr means reply

Added note confirms info was added to my spreadsheet and my Notes on each surname

This info is available by hovering over the little document icon next to each Matches name. It is very useful in its own right to help me keep track of each Match. It is also particularly valuable when reviewing a list of Shared Matches – you can easily see which ones you have notes for and what the notes say. This helps you decide if a group of Shared Matches are grouping around one ancestral line.

I do this pretty religiously for all Matches with Hints; and try to do it for all 4C Matches, too – no time is left for the tens of thousands of other AncestryDNA Matches.

[22I] Segment-ology: Format for AncestryDNA Notes TIDBITS; by Jim Bartlett

One Segment at a Time

A Segment-ology TIDBIT

The old saying: How do you eat an elephant? One bite at a time. We can, and should, apply this advice to Triangulated Groups and Chromosome Mapping. Take it a TG/segment at a time.

These days, the Matches are pouring in, and it’s easy to get overloaded with data. So I’m setting two goals:

  1. Form one new TG every day
  2. Communicate with the Matches in a TG each day

Each person’s objectives and available time are different, so set the timeframe to suit your own situation (every other day, each week or whatever). The point is to put a goal and plan in place.

There are about 400 TGs spread over my 45 chromosomes. So at one-a-day, it would be March 2018 before I could form every TG for my Dad (I’m just getting started on his chromosome map).  But by then this long ignored project would be done; and his map would provide extremely valuable information for my chromosome map.

And if I send out a small group email (average 10 Matches) to the most significant Matches in a TG every day, it will be March 2018 before I focus on every TG. But two good things will happen: 1) I will have focused on every TG, and worked on the Common Ancestor; and 2) For about every 10-20 emails/messages I send out, I determine a new Common Ancestor. So by March 2018 I’ll have another 200 or so Common Ancestors. [NB: Each CA is not necessarily the correct genetic link for the TG, but they are all genealogy cousins and provide important clues in our quest to “walk the ancestor back” and/or obtain multiple agreements on the TG CA.]

In other words, we reap what we sow – we get a percentage return on the communications we send to Matches – the more we send, the more we get in return.

Again, everyone’s situation is different. All I’m suggesting is to set a goal, and schedule some time for TGs and chromosome mapping. Take a periodic bite out of the atDNA elephant!


[22H] Segment-ology: One Segment at a Time TIDBIT by Jim Bartlett 20170218

Uploading to GEDmatch

A Segment-ology TIDBIT

There are 3 basic steps:

  1. Go to and create an account. Your account is based on your email (so carefully choose the email you’ll want to use), and a password (known only to you – if you forget it, you’ll need to reset the password). You’ll get your own homepage at GEDmatch, which will list any DNA kits you upload and/or any GEDcom.
  2. Go to your DNA company and download your raw DNA data file – note the name of the file and where it is saved (usually your Download folder); leave the file zipped (do not unzip it)
    • AncestryDNA – At “Your DNA Results Summary” page, click on top-right: “Settings” (gear icon); click on “Download Raw DNA Data” TAB and follow their directions, which will involve an email and entering your password again.
    • FamilyTreeDNA – on your main “Dashboard” page, under the Family Finder section is a link: “Download Raw Data” – click on that; and then click on the download arrow for “Build 36 Raw Data Concatenated”.
    • 23andMe – UPDATED (1/20/17) at GEDmatch just click on “23andMe fast and easy” – the process takes about a minute!
  3. Log into GEDmatch and upload your raw DNA data file – in top right box, click on “Generic Upload”; then fill in the form boxes, and be sure to check Yes (the default is No); then in the last row: Click on “Browse” means: Click on “Choose File” button. Do that and navigate in your PC folders to where your raw DNA data file is, and click on it. Then Click on “Upload”. Wait several minutes for the process to complete and give you a statement that it is finished.

Note: you can, and should, also upload a GEDcom file (your family Tree) – on your main GEDmatch homepage, see the link for “Genealogy – Family Trees”.

I hope to see you on GEDmatch!


[22G] Segment-ology: Uploading to GEDmatch TIDBIT by Jim Bartlett 20170119

Walking the Ancestor Back

A segment-ology TIDBIT

Here is an example of walking the ancestor back. I just extended one more generation today, giving four intermediate cousins all in the same line of descent from the CA.

The TG is [14B24] 18-30Mbp about 18cM – [14B24] indicates Chr 14, start in 10-20Mbp area, ahnentafel to CA starts 2-4 – some show this as PP]

The following line of descent is all in VA/WV [the four CAs are bolded]:

Common Ancestor: Sylvester WELCH 1696-1753; 1m 1720 Anne SPENCE: Match KBD at ADNA for 9.9cM is 6C1R

MRCA is son: Sylvester WELCH 1729-1810; m c1752 Jemima CARROLL; Match PDJ at FTDNA for 10.1cM is 5C

Dau: Elizabeth WELCH 1777-1847; m 1797 James FLEMING

MRCA is dau: Sarah FLEMING 1809-1854; m 1827 John H BARTLETT: Match LWA at FTDNA for 16.2cM is 3C

MRCA is son: James V BARTLETT 1836-1920; 1m Elizabeth J NEWLON: Match CK at 23andMe for 54.1cM is 2C1R [this segment overlaps the next TG, too]


Son: James V BARTLETT m Betty V BAKER

Son: jvb jr = me!


A Segment-ology TIDBIT

[22F] Segment-ology: Walking the Ancestor Back TIDBIT by Jim Bartlett 20170103