Are you wondering how to tell if an AncestryDNA Thrulines estimate is reliable, or even possible? The Thrulines algorithm works by comparing your DNA matches, their trees, and all the searchable trees in the Ancestry public member tree database. If the algorithm can make your tree and your DNA match’s tree connect somewhere, the hypothesis shows up in Thrulines. One problem with this is the many errors in the public member trees database. Also, Thrulines is a computer algorithm, not a genealogist. Sometimes it merges identities that should not be merged. Also, most of us have thousands of matches in the AncestryDNA database. Some of those matches are false, as explained brilliantly by Blaine Bettinger here:
Blaine Bettinger, “The Danger of Distant Matches,” blog post, 6 January 2017, The Genetic Genealogist (https://thegeneticgenealogist.com/2017/01/06/the-danger-of-distant-matches/).
I recently came across a Thrulines estimate that I wanted to check for accuracy. It was a Thruline for a cousin, Deanna, who shared her results with me.* I had not worked on her family tree or her matches much, so I had to do some work to determine if the Thrulines estimate was accurate. After finding that it was false, I made a list of criteria to determine if a Thrulines estimate is reliable or not.
*Deanna and her matches have all been privatized throughout this post.
-Most of the matches share over 15 cM: If most of the matches are under 15 cM, many could be false matches sharing a pseudosegment with you instead of an actual segment.
-Matches are grouped to the correct parent: if one or both parents have tested, the DNA matches in the Thrulines estimate should be grouped in the appropriate maternal or paternal group – a Thruline through your mother’s side should only include matches that say “Mother’s Side.”
-Matches form a genetic network: when you check the shared match lists or cluster report, you should see that the matches also match each other and form a network
-Documentary evidence points to a possible connection: the names, dates, and places for the known ancestor, potential ancestor and potential siblings look feasible
Possible Red Flags:
-Common surname: there’s an increased risk for erroneous merges by the Thrulines algorithm and in trees users created
-Potential ancestor lived before 1800: increased risk of errors in user submitted trees, more possible descendants to find among your thousands of matches
-No siblings: this is an obvious problem – if the only matches descend through your known ancestor, the most recent common ancestor of the matches is not the ancestor in the Thruline estimate
Thrulines Example #1 – Martha M. Silvius
One of the common types of Thrulines I see that are not helpful, though not necessarily erroneous, are the type with no siblings to our known ancestor. Here is an example from my Thrulines:
In my Thruline to Martha M. Silvius, all the matches are through my known 2nd great-grandmother. This is actually a Thruline showing evidence that Jessie Estelle Ross is my 2nd great grandmother. The only evidence that Martha M. Silvius is my 3rd great grandmother is from my tree and other trees – there are no DNA matches corroborating it. If this Thruline had additional siblings to my known ancestor, Jessie Estelle Ross, with DNA matches descending from them, then that might actually provide evidence about Martha being my 3rd great grandmother.
Thrulines Example #2 – Isaac Newton Wilson
The next benchmark to check is if most of the matches share more than 15 cM. The screenshot above shows matches who descend from Sarah E. Wilson, a possible sister to Arthusa Wilson. All except one match, Art, are over 15 cM, so much less likely to be false matches.
The next thing to check is if the Kat, Joe, Di, Nel, Jen, and Art are truly paternal matches, since this Thruline is supposedly through Deanna’s father. Deanna’s mother has tested at Ancestry, but not her father. We would then expect to see the maternal/paternal bucketing system say “no group assigned” instead of “mother’s side” on all of the matches in this Thruline.
I clicked on the matches with Kat, Joe, Di, Nel, Jen, and Art and found that none of them labelled “mother’s side.” As you can see in the example above, Sarah E. Wilson’s descendant, “Kat,” is not assigned to a group. We can then infer that because she is not in the “mother’s side” group, she is on Deanna’s father’s side. Another possibility is that she is a false match, but since she shares 22 cM, it’s less likely. Kat matches Deanna’s son and daughter also, who are labelled “Mother’s Side.” This is because they also match Deanna’s mother, which we would expect. The other shared matches don’t match Deanna’s mother, so they all appear to be paternal matches.
To confirm that the matches in this Thruline form a genetic network, I checked their location in a cluster chart called a network graph. I used Gephi to create the network graph with Deanna’s matches downloaded from the DNAGedcom client. Each colored cluster represents a genetic network – matches who also match each other. The idea is that each genetic network has a common ancestor or shared ancestral line. (To get your own network graph, contact Shelley Crawford of ConnectedDNA!)
The graph is zoomed out very far so you can’t see the nodes and lines connecting very well in the screenshot. The nodes/dots in the graph are Deanna’s DNA matches and the lines are shared match connections. When I zoom in, I can see nodes and labels with match’s names.
I searched the list of matches in Gephi and located Kat, Joe, Di, Nel, and Jen on the network graph. They are all located in salmon pink cluster at the bottom, showing that they are in the same genetic network. That network probably has Isaac Newton Wilson as one of the common ancestors. Other potential common ancestors for that cluster include Isaac Newton Wilson’s wife, and/or parents.
After evaluating this Thruline, I believe it is a good hypothesis. I can work toward proving it with documentary research and further evaluation of shared cM and relationships.
Thrulines Example #3 – Jeremiah I. Green
This is a another Thruline for Deanna to Jeremiah I. Green. At first glance, it looks good because there are matches through several siblings. When I looked at the matches coming from each potential sibling to Deanna’s ancestor, I realized that most of them were under 10 cM. Only eight of the thirty matches shared over 15 cM with Deanna. I was also wary that the surname Green is somewhat common and the potential ancestor, Jeremiah Green, lived in the early 1700s. To see if this Thrulines estimate could be accurate, I focused on verifying the traditional research for Deanna first.
Deanna supposedly descends through Jeremiah’s daughter Martha Mabel Green. When I opened Martha Mabel Green’s branch of the Thruline, I noticed that there were two generations of “potential ancestors” to evaluate before the line got to someone already in Deanna’s tree, Lucinda Harris. Deanna only had the following info for Lucinda Harris:
b. 1802 [place unknown]
married William P. Jones (1797-?)
Child: Francis Lily Jones
No sources, no parents, no other children, no place of birth or death.
The information on Lucinda was so sparse that I decided to started with Deanna’s mother and verified the parent-child links back to her great-grandmother, Francis Lily Jones. When I got to her, the trail became difficult to follow.
Francis Lily Jones married Newton Elijah Laster and they lived in Hawkins, Tennessee. I reviewed Lily’s death certificate from 1921 and it revealed the following perplexing information for her parents:
Name of father: Unknown Ligitimate
Birthplace of father: [blank]
Maiden name of mother: Lucy Jones
Birthplace of mother: Tennessee
As I continued to review the documentary research, I found many public member trees with Lily’s parents as James C. Jones and Lucinda Jones. They seemed to be part of a large Jones family in Hawkins County, Tennessee, and maybe were cousins who married each other.
Going back to the Thrulines estimate I clicked on John Early Harris possible father for Lucinda, keeping in mind how common the name Harris is. The sidebar opened, as shown in the screenshot above, with information to evaluate Martha Mable Green possibly being the mother of John Early Harris. The trees did show that a John Early Harris of Warren, NC was the father of a person named Lucinda Harris, whose spouse and children were unknown. This John Early Harris’ parents’ were Joseph Harris and Jane Egerton.
Another tree showed that a John Earley Harris of Granville, NC was the son of Isham Harris and Martha Mabel Green, but this John Earley had no children. Although both men named John Earley Harris had the same birth dates and death dates, there were clearly two separate men whose identities had been merged.
In reviewing sources for John Earley Harris, I found a FindAGrave memorial (with no headstone photo) for him that showed several of the siblings in the Thrulines. This was the family for Martha Mabel Green and Isham Harris. The other John Early Harris had a daughter named Lucinda Harris. The parent-child links in the Thrulines for this generation were not viable and were founded on the merging of two identities. Traditional research showed that Deanna’s didnt’ actually go back to Martha Mabel Green. So why were there so many matches to Martha’s descendants showing up in the Thruline?
Another criteria for a good Thrulines estimate is that the matches should be on the appropriate side of your family. Deanna’s Thrulines estimate to the Green family was supposedly through her mother, who has also tested at Ancestry, but hasn’t shared her results with me. However Deanna’s matches have been grouped so that those who also match Deanna’s mother say “mother’s side.” If the match doesn’t say “mother’s side,” there are only two other possibilities: it is a paternal match or a false match. When I checked J, D, V, R, and K, the matches descending through Martha Mabel Green, only one of them was an actual maternal match. See the screenshots below:
Update 11/16 8:45am: I learned that matches under 20 cM are not given a mother’s side or father’s side designation. So, I can’t assume that J is not a mother’s side match just because there’s no “mother’s side” label. I would have to look in Deanna’s mother’s matches to see if she matches J also. The same applies to the match between Deanna and K below, who share only 9 cM.
Many people have not had either of their parents test at Ancestry, so they can’t do this test. However you can still look at the shared match lists and see if the shared matches are known maternal or paternal cousins. This works well for matches over 20 cM, but under 15-20 cM, you may see some matches who are related on your mother’s side and your father’s side. This is why some of the matches above look like they could be maternal matches, but they are not.
For example, K supposedly shares 9 cM with Deanna. There are 4 shared matches – SongMom1647, Heather, RSmith2, and E.L. Two of the matches also match Deanna’s mother, and are put in the “Mother’s Side” group. The other two are not assigned to a group, so are probably paternal. Shared match lists don’t show you people who are all triangulating on the same segment and thus probably all have a common ancestor – they are just people who share DNA with you and with each other. They could have a different common ancestor between them than you have with each of them.
Another criteria for a good Thrulines estimate is that the DNA matches form a genetic network. You can check this by looking at each match and viewing their shared matches. You should be able to see some shared match connections between the matches. Shared match lists only go down to 20 cM, so you may not see any shared matches for some.
You can also check their location in a cluster chart or network graph, as I mentioned before. I found all the matches that were 14 cM and over in the Green Thrulines estimate, since 14 cM was the minimum threshold included in the graph. As I mapped each of their locations on the graph, I was not surprised to find that they were not located in the same part of the graph. Some were located in or near maternal clusters, others were located in paternal clusters, and some were in a blob in the center that probably includes some false matches who seem to match several clusters.
My conclusion: this Thrulines estimate is inaccurate. Not only did the documentary sources show the parent-child links were based on merged identities and erroneous trees, but the analysis of maternal/paternal groupings of matches showed that the matches were not on the maternal side. The cluster analysis showed the matches did not appear in the same genetic network. This Thrulines estimate had the following red flags:
-The potential ancestor was born before 1800
-Most of the 30 matches were under 15 cM:
8-15 cM: 22 matches
16-30: 7 matches
30 +: 1 match
–The matches didn’t match the correct parent
-The matches didn’t group into a genetic network
So, beware of Thrulines estimates! Even though they might look good at first with thirty matches descending from multiple siblings. If many matches are small matches, the Thrulines estimate could be false.
Good luck as you evaluate your Thrulines!
In the Deanna vs. K photo, it would never say mother’s side. The Mother/Father side designations only apply to shared DNA matches of 20cMs or more. Deanna and K & Deanna & J only share 9cMs so you would never see a mother/father designation there. So you can not assume that it is a paternal or false match just by that. It is also possible that the segment was timbered for the mother and not the child and caused it to not be a match for the mother but it is still showing up for the child. You would need a chromosome browser to sort that match out to see if it is shared with the mother.
Wow – that was a lot of effort to assemble this very helpful and clear post! Thanks for sharing; it will be valuable to so many!
This is definitely useful for the US folks out there.
It assumes the “luxury” of many matches over 20cM. The reality of European continental matches is such, that many of the conditions cannot be met
– consider only segments above 15cm (there are a few!)
– verify Mother’s side labels (most matches are below 20cm and miss these labels)
– forming a genetic network (ancestry only reports ICWs above 20cm, the genetic network often cannot be established)
Therefore, it is usually trickier to assess any poossible TL. What works best for me is leveraging other sites and taking into account chromosome mapping. Naturally, that can’t be assumed for many Ancestry only matches.
In that case, we’re often left with no evidence if the DNA supports a known paper connection (obtained and verified through traditional means) or comes from a different CA.
Thanks so much. I was starting to get fairly interested with some of the thrulines just based on feasible siblings, etc. One thing that stumped me for a bit from your article is the mothers line/father’s line evaluation. I’m fortunate that both of my parents were able to test, so I default to working from their dna. In this scenario it seems the program has nothing to base maternal or paternal lineage on, so it doesn’t even say “no group assigned.” So, unless I’m missing something, in my situation I will need to refer to my own dna thrulines to check that aspect of the assessment.
Robert, many people are in the same boat. If you are using your parents’ DNA, then you will not be able to know if their matches are “mother’s side” or “father’s side” by looking for that label. Instead you would do analysis of which genetic network they are in by looking at shared match lists. Good luck!
Thank you for guidance on interpreting ThruLines information. My wife’s Ancestry tree proposes over 200 potential ancestors. Way too many of the matches on these various branches are under the 15cM threshhold.
I have a small number potential ancestors suggested on my ThruLines associated with my current Ancestry family tree. My current tree–just my father’s side due to the ethnicity being very different than my mother’s side. Is it possible to have ThruLines also on a tree for my mother’s side or do I need to have but one tree combining both paternal and maternal lineages? If I share my tree with siblings, will they have ThruLines? Their results should be different because the shared matches will vary among siblings. Thank you!
As far as I can tell, once you disprove a Thrulines hypothesis as you did above, there is no way to signal a “rejection” of the evaluation on the Ancestry site.
One of the best ways to get inaccurate Thrulines to disappear is to update the family tree attached to our results with more specific information. In example #3, my cousin Deanna could fix the inaccurate mother for Francis Lily Jones. As soon as Lucinda Harris is gone from her tree, I suspect the Thruline would disappear.
We can also invite others to fix their trees when they have merged people with the same name.
I misunderstood how they had created this matching and Thrulines and thought it was based on more rigorous data matching the pairs of matches. Fortunately I just started but it should start with a caveat/warning – I searched for how it works and found your article, very helpful thankyou!
A clear issue is using members trees, there are huge inaccuracies, probably people clicking the “helpful” buttons on hints etc and linking people who have the same name but are not directly related. I just made a big mistake which is how I spotted it, untangling the connections I just added is still ongoing as I don’t know what I had before, so I’m having to work out the genuine data and delete/disconnect the bad.
Note to self: validate everything.
Fantastic analysis of Thrulines. Thrulines will hopefully improve as users submit better data.
I made my tree private because Thru Lines was absolute trash. They said my 2nd Great Grandfather was my daughter’s 3rd Great Uncle. Everyone of my grandparents siblings were listed as half brothers and sisters when we have DNA from Ancestry, 23and Me, and FTDNA to disprove that plus all family records for birth, baptism, marriage, death. A Thru Lines suggestion for a 3rd Great Grandfather had a couple who had a son with his name but that son was married to two different women whereas my Great Grandfather was married once. The other guy had no son with my documented 2nd Great Grandfather’s name. ThruLines is someone with a few strands of DNA who have wrong information being forced on you. Thru Lines were using information I got from a Catholic marriage record with parents names as ancestors when I had no information on them other than their names. I ended up deleting them. I kept finding Ancestry trees with living relatives on Google so that is when several relatives made our trees private. Now there are people who are not DNA matches latching onto our relatives when they had their own. DNA Circles were much better because you had to have DNA and documentation to be in them. I have Thru Lines slandering and bastardardizing my relatives which is disgusting. I cut my membership back to cheapest one and told them it was due to their Thru Lines lies.
EXCELLENT article! Very helpful!
Great article! Just a couple of small points.
It is possible to have an ancestor born before 1800 on Thrulines that go out to 5th great grandparents. All my 5th and most of my 4th were born in 1700’s. Even my 20-something kids have 5th great grandparents born before 1800. The average length of my family generations is 28 years. It would look like this:
1960 – Child
1932 – parent
1904 – grandparents
1876 – great grandparents
1848 – 2nd g. grandparents
1820 – 3rd g. grandparents
1792 – 4th g. grandparents
1764 – 5th g. grandparents
An actual line from my tree:
Great Grandfather: 1889
2nd G. Grandfather: 1848
3rd G. Grandfather: 1818
4th G. Grandfather: 1777
5th G. Grandfather: 1745
And, then, there is this line:
Great Grandfather: 1879
2nd GGrandfather: 1847
3rd GGrandmother: 1822
4th GGrandmother: 1782
5th GGrandfather: 1723
Let’s get hypothetical with fathers having babies at 50 years of age: Starting with 1950 it would go like that:
Great Grandparents: 1800
2nd Greatgrandfather: 1750
3rd Greatgrandfather: 1700
4th Greatgrandfather: 1650
5th Greatgrandfather: 1600
Could you explain why you believe ancestors born before 1800 probably indicate error? Just because you have to dig deeper, does not mean it is not possible or even probable. I would not have a tree at all if I believed this.
Thank you for this. I have several pre-1800 Thrulines that are mostly correct; I just wanted to point out the general idea that the further back in time the Thruline ancestors are, the more chances for error there are with the family trees in the Thrulines due to less records and more difficult documentary research. In my experience there are more errors in the trees and Thrulines of ancestors who lived further back in time.
Do you have any idea of the birth date tolerance within ThruLines for a common ancestor. Here is the problem. I have many DNA matches at a certain ancestor’s various children. The ThruLines was also reflecting the majority of them. However, after I did further research on the ancestor, I found him to be at least 10-15 years older than previously thought. Well, since all of the descendants used the same birthdate of 1752 and I changed his birthdate to about 1740, I lost all of the ThruLine connections despite remaining DNA connections (obviously) and our trees still having the same people.. I simply made his birth year more closer to accurate. There were 45 connections previously, now 0. Not like I can contact all 45 to give them the newly found information. I almost have to keep my tree inaccurate in order to keep the common ancestor in ThruLines, or hope for them all to read my conclusions and update their trees. There must be a better solution. Argh. Thank you for any answer.
Rick – that’s frustrating. If I were you, I would change the birthdate back to what it was, capture the Thruline through screenshots and a research log to the match page of each DNA match in the Thruline, and then update your tree to have the new birthdate.
However, if you want to always have access to the Thruline to get new DNA descendants, you could try adding all their descent lines to your tree to see if that helps preserve them even after you update the birth.
Another option is to include the new, more accurate birthdate as an alternate fact.
When Ancestry.com gives out these surveys I always mention constantly that they should update the TruLines feature for accuracy and research tips. For my findings they have been accurate so far because I am using both Ancestery DNA and 23andMe to compare possible cousin matches on both platforms. I know that these companies have different algorithms, but they still show the same cousins poping up on both platforms.
I’m the daughter of an adoptee and part of why I got into geneaology was to find my paternal grandparents; my grandfather through 23and Me and my grandmother through Ancestery.com.
That’s great that you’ve been able to recognize some common DNA cousin matches on both Ancestry and 23andMe. Good luck as you continue your research.