Recently I used the ‘DNAPainter‘ What Are the Odds Tool to place a DNA match in my tree and to identify her father.
M showed up in Greg’s list of matches at Ancestry.com. She and he shared 29 centimorgans of DNA across 2 segments, but she had no tree associated with her DNA. Her kit was administered by a 3rd person, D.
M and Greg’s shared matches were all cousins I knew, all of them associated with the Young branch of his tree. M also shared DNA with Greg’s Aunt Betty: 48 centimorgans across 4 segments. M and Aunt Betty had 14 shared matches. More than ten were known cousins all linked to the Young family tree.
I messaged D and she replied that M was born in outback Queensland and that M’s father was unknown. I knew of no relatives who came from there.
48 centimorgans of shared DNA is associated with a range of possible cousin relationships. It was not at all clear how M and Aunt Betty (and Greg) might be related.
I asked D to share a screenshot of M’s shared matches with Aunt Betty. I thought that if I knew how much DNA M shared with some of our known cousins I might be able to identify how M might be related.
One of the shared matches, that of J, jumped out. J is Greg’s 3rd cousin and is descended from one of the daughters of George Young and Caroline Young born Clarke. M and J share 815 centimorgans and so can be estimated to be 1st or 2nd cousins. Other known cousins also shared significant amounts of DNA with M, including F who shared 277 centimorgans and R who shared 443 centimorgans. Based on the amount of shared DNA F and R are estimated to be 2nd cousins to M.
I drew up a tree in the DNAPainter What Are The Odds tool, placing Betty and Greg and also J, F, R (and as well, K and B. I know how these are related.) K shares 60 centimorgans with M and B shares 55 centimorgans with M. Using the What Are The Odds tool you add how much DNA is shared between the match and the target name. The aim is to place the target on the tree.
The numbers below each name or initial are the number of centimorgans of DNA that person shares with M.
I then switched to version 2
see orange arrow for where to click to switch to version 2green arrow shows where to click for suggest hypotheses in version 2 of the tool
and then clicked on ‘suggest hypotheses’. The tool suggested 10.
This is the tree showing the 10 hypotheses.Scrolling down below the tree there is a table showing a matrix of the matches of M with how M hypothetically relates to those matches.
Rachel lived from 1865 to 1918. M cannot be her child, so hypotheses 8 and 10 shown by the blue and green arrows are implausible. It is possible that M could be a grandchild of Rachel, but hypotheses 6 and 7, shown by the orange arrows, have much lower scores than other hypotheses, and so I removed them too. When removing hypothesis 8 though I did not delete that person on the tree but I removed the option that it was a hypothesis.
I am left with six hypotheses.
If I scroll down I get a ranking of hypotheses.
Scrolling further I get the table with a matrix showing the odds associated with each hypothesis and the various matches.
It can be seen that hypothesis 2 (highlighted in orange) is the most likely. J is most likely a first cousin of M, our target who we are trying to place on the tree. The next most likely hypothesis is that M is a half-aunt of J.
I know from my knowledge of the family tree that J does have a full uncle, brother of J’s parent M and showing as unknown sibling child of Leslie on the tree. Thus hypothesis 2 is possible from a genealogical perspective.
I checked the electoral rolls for the period that M was born and for the location. I found that the unknown sibling was indeed living in that part of Queensland at the relevant time. M’s mother had suggested the surname of M’s father. It was similar to the surname of J’s uncle.
On the basis of the calculations of What Are The Odds tool and a review of the broader circumstances, I am reasonably confident that hypothesis 2 is plausible. M is the 1st cousin of J. She is Greg’s 3rd cousin.
This afternoon I watched a Legacy Family Tree webinar (recorded) by Dr Blaine Bettinger, a genetic genealogist, about a DNA technique used to map the segments of DNA that a person does not share with a match. A match, of course, is definable as a string or strings of DNA common to two people. But what about the DNA that they do not share? Can it tell us anything?
Blaine Bettinger showed how, by using DNA information from close relatives such as parents or siblings, we can work out where pieces of DNA came from: how they were inherited. The technique is called deductive mapping, inverse mapping, or inferred mapping.
The key is to recognise that on the chromosome you inherited from your father, your DNA comes either from your paternal grandfather or your paternal grandmother. Similarly, the DNA from your mother comes either from your maternal grandfather or your maternal grandmother.
If you find DNA on the chromosome that you inherited from your father that did not come from your paternal grandfather then it must have come from your paternal grandmother. The principle applies equally to matches on your mother’s side.
I was very keen to put this new technique to the test on my husband Greg’s DNA. Luckily, Greg’s brother Dennis had tested his DNA, and I was able to use his matches in combination with Greg’s. The first match I reviewed was Greg and Dennis’s paternal aunt Betty.
Note Aunt Betty and Peter, father of Greg and Dennis, are half siblings. Betty and Peter have the same father but different mothers.
My hypothesis was that for segments of DNA where Dennis shares DNA with Aunt Betty and Greg does not share DNA with Aunt Betty, those segments must have been inherited from Greg and Dennis’s paternal grandmother, Peter’s mother Elizabeth Cross.
All segments on Greg and Dennis’s paternal chromosomes were either inherited from their paternal grandfather Cecil Young or from their paternal grandmother Elizabeth Cross. If Dennis shared a segment with his Aunt Betty, he inherited that segment from Cecil. If Greg did not share that same segment with his Aunt Betty, then he did not inherit that segment from Cecil. He must have inherited the segment from his paternal grandmother Elizabeth Cross.
Using the tools at MyHeritage DNA I was easily able to extract the segment data of the DNA shared by Greg and his Aunt Betty. They share 138.5 centimorgans of DNA across 19 segments. I scrolled down to the chromosome browser on the match screen and clicked on “Advanced Options” on the right side of the screen and then clicked on “Download shared DNA info”.
This gave me a spreadsheet and I was able to copy and paste the data into DNA Painter (I have written about chromosome mapping with DNA Painter at DNA Painter – a new tool). I created a new profile for this exercise as I did the calculations.
Map of the DNA segments Greg shares with his Aunt Betty using DNAPainter
I then extracted the segment data for Dennis and Betty.
I then mapped Dennis and Betty’s match at DNA Painter. So I could see Greg and Betty’s match lined up against Dennis and Betty’s, I mapped it as a maternal match. I then looked for the visual clues of segment mismatch. I have highlighted these segment mismatches with green arrows. There were eight segments where Dennis shared DNA with Aunt Betty that Greg did not. (There were also segments that Greg shared and Dennis did not but for the moment we are concentrating on Greg’s chromosome mapping.) Four of these were complete segments and four partial segments.
I took the spreadsheet of Greg and Betty’s shared segments and pasted beside it Dennis and Betty’s shared segments so I could compare them.
Data from MyHeritage
I then highlighted the whole segment mismatches in green and the partial segment matches in purple.
I then added the four segments that were inferred to have been inherited by Greg from Elizabeth to the DNA Painter profile. I only needed to add the chromosome number and the start location and end location.
For the purposes of chromosome mapping I did not need the additional data concerning RSID start and end, the number of centimorgans, or SNPs.
When previewing the segments I got a warning from DNA Painter about match segments being overlaid and that I might have already mapped these segments.
When I tried to save the match, DNA Painter told me that there was an overlap with the segments I had already painted of Dennis’s match with Aunt Betty.
The four new segments showing DNA inferred to be inherited from Elizabeth Cross are in shown in green
The next challenge was to calculate the partial segments where Dennis shared some DNA with Aunt Betty that Greg did not at the beginning or end of a segment. I first did the calculation for Chromosome 5. The segment Dennis shared with Aunt Betty extended beyond the segment Greg shared with Aunt Betty. In the spreadsheet calculations for inferring the DNA Greg inherited from Elizabeth Cross, I copied the end location data for Greg’s segment match with Aunt Betty and the end location data for Dennis’s segment match with Aunt Betty. This created the segment that Dennis shared with Aunt Betty and Greg did not.
I painted that segment successfully. The black arrow highlights the segment Greg does not share with Betty and can thus be inferred to have been inherited from Elizabeth Cross. Underneath can be seen that Dennis shares that segment with Betty.
I repeated the exercise for chromosome 11. This time Dennis shares DNA with Betty and Greg does not before the segment Greg shares with Betty. So the calculation involved the start location of Dennis being the start location of the inferred segment and the start location of Greg’s match with Betty being the end location of the inferred segment.
I repeated the exercise of inferring segments for the remaining two segments.
The finished profile showing Greg’s match with Aunt Betty in purple, Dennis’s match with Aunt Betty in orange and in green the inferred inheritance of DNA by Greg from his paternal grandmother Elizabeth Cross based on the mismatch of Greg’s match with Aunt Betty when compared to the shared DNA of Dennis and Aunt Betty
I was confident in the logic of the results of this deductive chromosome mapping exercise and added the inferred segments to Greg’s DNA chromosome map. Before this exercise I had mapped 40% of Greg’s DNA with 161 segments being assigned. After adding these 8 segments 41% with 169 segments assigned. I have now mapped 54% of Greg’s paternal chromosome with 94 segments assigned.
I look forward to continuing the exercise and filling in more gaps.
By assigning inferred segments to either the paternal grandfather, paternal grandmother or on the maternal chromosome to either the maternal grandfather or maternal grandmother, I may be able to use the information to deduce how a DNA match links to Greg’s family tree based on the segment shared, even if that match does not have a family tree link to Greg.
A chromosome map is not just a colourful diagram. It’s a useful tool for exploring how DNA matches might be related. Information about the descent of a DNA segment, even if the segment is not directly shared by matches, could help you to calculate their shared ancestry.
The genealogy company MyHeritage recently announced it had refreshed the data for its ‘Theory of Family Relativity™’, a tool that computes hypothetical family relationships from historical records and DNA matches. It does this by ‘…incorporating genealogical information from [its] collections of nearly 10 billion historical records and family tree profiles, to offer theories on how you and your DNA Matches might be related.
In yesterday’s webinar I looked at a MyHeritage theory of the relationship between my husband Greg and his cousin Pearl. MyHeritage suggests that Pearl is Greg’s second cousin once removed. This is confirmed by the historical records. Greg and Pearl have well-developed and reliable family trees, so it wasn’t difficult to calculate the relationship.
It’s hard to say what’s new in MyHeritage’s new Theory. It’s possible that new ways of massaging the data have been developed, but it seems more likely that, with larger volumes of data being processed to develop Theories, ‘new’ simply means more, as in ‘newly-added’.
Anyway, I thought I’d give it a try.
MyHeritage’s announcement included a note advising users that ‘If we have found new theories for you in this update, you’ll see a banner about the Theory of Family Relativity™ at the top of your DNA Matches page. Click “View theories” to see all the theories we’ve found, both old and new.’
I couldn’t find this banner, but I eventually found my way to the filters on the DNA results page where by using the “All tree details” filter, I could select “Has Theory of Family Relativity™”
1 choose DNA from top menu bar – 4th option, 2 choose to look at DNA Matches, 3 select filters, 4 click on “All tree details and from the drop down menu select the top option “Has Theory of Family Relativity™” indicated by the green arrow
My husband Greg has 14 matches with theories. Back in March 2019 I counted 7 matches with theories so I looked at this list of matches again to see if I can learn anything new. In March 2019 Greg had 4313 DNA matches at MyHeritage. Now he has 6399, 50% more.
Several of the 14 matches in the list were matches I had not previously reviewed. I decided to look at S, whose DNA kit is managed by T from Canada.
2 of the 14 matches which have a Theory of Family Relativity: in the post I have looked at the second match in this listcloser view of screenshot of the 2nd match
Greg and S share 35 centimorgans across 1 segment. MyHeritage estimates them to be 3rd to 5th cousins. S appears in a family tree with 250 people. S is the 4th cousin of Greg according to the Theory of Family Relativity™. Ancestral surnames appearing in both trees include Dawe; Daw and Smith. Ancestral places common to Greg and S include Great Britain and Ireland.
I clicked on View Theory which I have highlighted with the green arrow.
There are three paths to support the theory that Greg and S are 4th cousins.
The first path uses 3 websites: my tree, a tree by B R from Australia and the third website the tree by T who administers the DNA kit for S. MyHeritage states “This path is based on 3 MyHeritage family trees, with 55% confidence”
The green arrow highlights that there are three paths to review, the first path is displayed. The letters a and bshow the links between the trees and there is a confidence level that they have a match between the trees which is shown immediately above the letters a and b.
The link is William Smith Dawe (1810-1977), Greg’s third great grandfather. I have on my tree that he is married to Mary Way (1811 – 1861). B R’s tree has William’s dates (1819 – 1877) and has William’s wife as Elizabeth Hocken 1821 – 1884 and the daughter of William and Elizabeth as Thirza Dawe 1824 – 1891. Thirza is the great great grandmother of S.
MyHeritage thinks the probability that the two William Smith Dawe’s on my tree and B R’s tree is 100% despite the differing birth dates. MyHeritage thinks the probability that Thirza Daw on B R’s tree is the same Thirza Daw on T’s tree is only 55%. I clicked on the small 55% immediately above the green letter b and got the following pop-up.
I have highlighted the 55% confidence with a green arrow up the top. Both Thirza’s have the same birth and death dates and places. The significant difference between the two Thirza’s is their parents. In B R’s tree Thirza is the daughter of William Smith Dawe and Elizabeth Dawe born Hocken. In T’s tree Thirza is the daughter of Isaac Smith Dawe and Betsy Dawe born Metters or Matters
There are several problems with this first path of the theory calculated by MyHeritage. I don’t believe our William had two wives and Thirza born 1824 would have been born when William and Elizabeth were extremely young. I know this family does have common names and these are repeated across several generations. There are also several cousin marriages in this branch of the tree.
I looked at the second path to see if it is more plausible. MyHeritage states “This path is based on 4 MyHeritage family trees, with 70% confidence.”
The four trees are mine and the tree by T who administers the DNA kit for S plus a tree by JS from Australia and a tree by MT from Australia.
This path goes from Greg’s great grandmother Sarah Jane Way (1863 – 1898) to her mother Sarah Way née Daw (1837 – 1895). The Daw surname sometimes is spelt with an extra e as in the tree by J S. From Sarah Dawe on J S’s tree we go to Sarah Ellen Dawe (1837 – 1895) on the tree by M T. I am not sure where the middle name came from. I don’t recall it on any document. I will check the documents I have.
M T’s tree has the parents of Sarah Ellen Dawe as Betsey Metters 1792 – 1863 and Isaac Smith Dawe 1795 – 1851. From Isaac we link to T’s tree. He shows Isaac Smith Dawe 1797 – 1851 and Betsy Metters (Matters) 1792 – 1863 as the parents of Thirza Daw 1824 – 1891, the great grandmother of S.
This theory seems more plausible to me, but I need to verify this against source documents. At the links between the trees MyHeritage assigns a confidence level. Most of the links are 100% but MyHeritage is only 70% confident that Sarah Dawe in J S’s tree is the same person as Sarah Ellen Dawe in the tree by M T.
I clicked on the 70% and got the popup showing the comparison which gives additional detail from both trees. The difference is that the tree by J S has no parents has no parents but the tree by M T has Sarah Ellen Way’s parents as Isaac Smith Dawe and Betsy Metters. M T’s Sarah Ellen Daw has the same dates and places of birth and death as the Sarah Daw in my tree. I have plenty of documents to back up that sarah’s parents were not Isaac and Betsy but instead Isaac’s brother William Smith Daw.
This theory almost but not quite adds up. The need to go across several surnames is because of the spelling variations between Daw and Dawe. In my tree I have spelled the surname without a final ‘e’. I think MyHeritage has placed too much emphasis on the surname variation and not enough on other variations.
The third path “…is based on one community tree and 4 MyHeritage family trees, with 52% confidence”.
This path uses our tree, the tree by Greg’s cousin Pearl, a tree managed by S R from Great Britain, Family Search Family Tree, and the tree by T who administers the DNA kit for S.
Pearl’s tree provides the link between Sarah Daw on our tree spelt without an e to Sarah Dawe with an e and from there to her father William Dawe – surname with a final e. From there the link is to S R’s tree with William Smith Dawe (1810 – 1877), MyHeritage are only 72% confident they have the right man. William Dawe is not a direct forebear of Pearl and she has not provided many details for him in her tree.
S R shows Thirza Dawe (1824 – 1891) as the daughter of William Smith Dawe. From there the link is to FamilySearch Family Tree but with only 52% confidence. I clicked on the 53% to find out why MyHeritage is not confident they have the same person.
There are some important differences. The dates are the same and the place name variations are minor. FamilySearch, however, has Isaac Smith Dawe as the father of Thirza, not William Smith Dawe.
This path is rated 52% confidence by MyHeritage. The level of confidence is determined by its assessment of the weakest link.
I don’t think this path is correct. S R’s tree shows William Smith Dawe fathering Thirza when he was only 14, which is unlikely.
Of the three paths I think path 2 is most plausible but even then it is not quite right as it relies on the wrong father for Greg’s great great grandmother Sarah Way born Daw and does not fit with known records.
The next step is to review records and update my own tree using those records. After all, the Theory of Family Relativity generated by MyHeritage is meant to be a hint and not a proven conclusion.
I did not have Thirza Daw(e), the great great grandmother of S in my tree.
I have Isaac Smith Dawe (abt 1797 – 1851) and his wife Betsy Metters (1792 – 1863) in my tree. They show as Greg’s 4th great uncle. I have only one daughter showing for that marriage, the forebear of another match. Because Isaac is off to one side I have not researched all that family.
Isaac Daw appeared on the 1841 English census as a 40 year old miller living at Newton Mill, Tavistock, Devon. In the same household was Betsy Daw aged 45, and four children Betsy Daw aged 15, Honor aged 9, Jane aged 8, David aged 4.
On the 1851 census Isaac S Daw is a 54 year old miller employing 4 men and 1 boy living at Lumburn, Tavitock. In the same household are his wife Betsy aged 58, a niece aged 15 and a servant, a miller’s labourer, aged 30. All children have left home.
At the time of the 1841 census there may have been other children who had already left home.
Research by another cousin Lorna Henderson which she shared to Wikitree showed “entry in Beer Ferris in Tavistock parish register for 25 Aug 1818 shows Isaac Smith Dawe as sojourner of this parish, and Betsey Metters of this parish spinster, “married in this church by banns with the consent of their parents” by Harry Hobart, Rector. Both signed: Isaac Smith Daw and Betsey Matters. Wit: Humphrey Roberts, Mary Box (neither of whom witnessed other marriages on the page)”. I navigated to the Wikitree entry from MyHeritage when I searched Isaac Smith Dawe (Daw)/Dawe in All Collections. MyHeritage has 13,676,346 results for Isaac Smith Dawe (Daw)/Daw – far too many, the problem with a common name – they would of course be reduced as one narrowed down the search parameters.
I have been in correspondence with Lorna Henderson before and I know she is a most conscientious researcher and that Isaac is her direct forebear. She has a website for her family history at http://LornaHen.com and the details she has researched about Isaac Smith Daw are at http://familytree.lornahen.com/p28.htm . Lorna records there that in his will of 1847, William Smith Daw mentions his daughters: “My Daughters Names are as follows Mary Cook Betsey Bennett, Thirza Daw, Honor Daw and Jane Daw” and also his sons “my too sons Isaac Daw and David Daw”.
I could not find a baptism record for Thirza Daw in the MyHeritage record collections. On Wikitree cousin Lorna recorded that Thirza Daw was baptised 5 APR 1824 Tavistock, Devon, England. I found an image of her baptism in 1825 at FindMyPast. She was the daughter of Isaac Smith and Betsy Daw. Their abode was Newton Mill and Isaac’s occupation was Miller. I have updated Wikitree with the slightly revised date.
I am confident that Thirza is the daughter of Isaac Smith Daw, Greg’s 4th great uncle. Thyrza Daw shows up on the 1841 census as a female servant in another household. She married in 1850.
I traced down to S through English and Canadian censuses and other records. I found that she was Greg’s 5th cousin. S and Greg share 4th great grandparents Isaac Daw(e) 1769 – 1840 and Sarah Daw née Smith 1774 – 1833. Greg is descended from William Smith Daw 1810 – 1877 and S is descended from his brother Isaac Smith Daw 1797 – 1851.
I will update my family tree at MyHeritage. The Theory of Family Relativity won’t update straight away but at least I know that the next time it updates it may use the opportunity to trace a more accurate path.
As mentioned above I feel the algorithms MyHeritage used placed too much emphasis on the variation between Daw and Dawe and not enough emphasis on the parents named in the trees though there was obviously some weighting for variations in parents.
Nothing has changed about the MyHeritage theories particularly that I can see although I had not noticed previous theories that I reviewed making use of the tree at FamilySearch.
The Theories of Family Relativity generated by MyHeritage are just that, theories or hints. But they did point me in the right direction to make the connection between S and Greg and build my tree a little further.
Last November I agreed to give a webinar (Web-seminar) – a live Internet presentation – for the genealogy company MyHeritage. Scheduled to be broadcast on Tuesday, September 22, 2020, it was to be called “Finding new cousins and building your family tree with DNA”.
The webinar was to start at 2 p.m. North American Eastern Time. I can’t remember if I realised that this would be 4 a.m. here in Ballarat.
What with bushfires and a pandemic I’d forgotten about this. Then last Friday I got an email scheduling an audio-visual test of the webinar software and hardware. It was on.
The walk-through went well, with only one hiccup: my Macintosh was reluctant to give microphone permissions to the webinar software. I gave up trying and used my Windows laptop instead.
My presentation was based on several posts, especially:
To comply with the convention that living people should not be identifiable, I asked the few people affected if they would mind being referred to by forename only. No one refused and I am very grateful. I also spent some time blurring their surnames where these were visible in screenshots and also blurring the details of other DNA matches.
My webinar was about using the MyHeritage DNA tools. Users interact with a web page for this. It’s complicated, and people new to it sometimes struggle to understand what’s going on. I tried to explain, emphasising that:
Find your matches where you know how you are related. MyHeritage has 4.2 million DNA kits in its database. You do not match all of these people but the number of matches you do have is probably overwhelming. Work from these known matches on to the matches you share with these matches.
Build or upload your family tree and link that tree with your DNA kit. If you are trying to work out how a match might be related you may need to work on their family tree to find the path to your shared most common recent ancestors and also to ensure there are no other possible relationships that could explain the shared inherited DNA.
There is a lot of data on the website and you have to explore often by scrolling down, and by clicking on the screen to reveal more even when there are not obvious prompts.
I pointed out the messaging icon and also the notes icon. Not everybody responds to your messages but many do. I recommend keeping the message short and offering to work with your match to find your shared ancestry.
I use the notes facility to keep track of when I messaged somebody and if I had received a reply plus any brief thoughts I might have about how they are related.
I looked at some of the tools MyHeritage offers: my favourite is the AutoClusters tool, an automatic tool that organizes your DNA Matches into clusters that likely descended from common ancestors. The tool was developed by Evert-Jan Blom and I have previously looked at the tool in my post DNA: experimenting with reports from GeneticAffairs.com.
All in all, it went well. The feedback was good. Most people found the session useful and in line with their expectations.
Next time I’ll use a headset for better quality audio and I’ll show simpler slides. And I will try to make sure the navigation tool for the presentation does not pop up.
AncestryDNA announces changes to its matching policy
From time to time users of the AncestryDNA service are confronted by a message advising that:
Our backend services are overtaxed at the moment and we are unable to retrieve all your matches. We apologize for the inconvenience, please try again later.
At other times users are told, “Something went wrong. Try reloading the page in your browser, or come back later.”
Refreshing the page often fails to work and users are forced to accept the invitation to ‘come back later’. Sometimes even the less specialised Ancestry.com site becomes overwhelmed.
AncestryDNA has more than 18 million samples in its database. It uses enormous computer power to store data and compare DNA. This is costly, of course, and where its methods produce false positives, inefficent.
Recently the company announced that it will no longer provide details of matches with only one segment where that segment is smaller than 8 centimorgans. The company gives as the reason for this new policy that
the shorter the length of the detected IBD segment (expressed in genetic distance), the less likely it is that the detected chromosome segment is truly inherited from a common ancestor.
AncestryDNA Matching White Paper Last updated July 15, 2020 – Discovering genetic matches across a massive, expanding genetic database
AncestryDNA notes that:
it has “…changed the [minimum] amount of DNA you need to share to be considered a match with another individual to 8 cM”.
from late August “…you’ll no longer see matches or be matched to people who share 7.9 cM or less DNA with you unless you’ve messaged them and/or included them in a note, or added them to a group (including your starred group).”
the change has been delayed “…until late August so you have time to review and determine if you want to save any very distant matches by sending them a message and/or including them in a note or group”.
Definitions, and what the AncestryDNA announcement means
A centimorgan (cM) is “a map unit used to express the distance between two gene loci on a chromosome. A spacing of one cM indicates a one percent chance that two genes will be separated by crossing over.”
The more centimorgans person A shares with person B the closer they are likely to be related. Your chromosomes have a total length of about 7400 cM, so you share about 3700 cM with each of your parents. Two people who share 6 to 7.9 cM are likely to be about 6th cousins, that is, they possibly share 5th great grandparents.
If you are related to a DNA match then the DNA segment or segments you share with at least one other person are identical by descent (IBD); you and your match inherited the segment from a common ancestor without recombination, and the segment has the same ancestral origin for you and your match.
The blogger Roberta Estes has estimated that 18% of her total matches share 7 cM and 30% share 6 cM. AncestryDNA’s purge of matches smaller than 8 cM will reduce her number of DNA matches by nearly half.
It has been estimated that about half the matches in the 6 to 7 centimorgan range are false positives. These matches do not truly demonstrate inheritance from a common ancestor. An error might have occurred when the DNA testing company compiled the chromosome marker: the DNA variations or the series of single nucleotide polymorphisms (SNPs) .
The companies’ matching algorithms do not treat the paternal and maternal chromosomes separately. Consequently consecutive SNP results for a short segment of DNA may appear to be half-identical in two individuals when in actuality the DNA sequences are not identical because the SNPs match on opposing chromosomes or because of errors in the matching algorithms. False matches can be the result of pseudosegments (matching alleles zig-zagging backwards and forwards between the maternal side and the paternal side), compound segments and fuzzy boundaries.
DNA is inherited so a match must also match one of our parents
If a person appears to match me but does not also match either of my parents, something has gone wrong in the matching process, for if neither of my parents shared the segment that appears to justify our match that person and I did not inherit the segment from a common ancestor.
The blogger Debbie Kennett found that 54% of her matches in the 6 to 7 cM range were not shared by either of her parents.
If about half of all DNA matches in the AncestryDNA database are very small and about half these are false positives, then about a quarter of the matches in our list of matches are false positives and are not genealogically relevant.
My experience
On 15 August 2020 I had 25,434 DNA matches to individuals. With 125 of these people I share 20 Cm or more. There are 25,309 distant matches with whom I share between 6 and 20 cM. Unfortunately there is no way using AncestryDNA to count matches in the range of 6 to 8 cM.
As both my parents have had their DNA analysed I am able to look at my very small matches to assess whether they match either of my parents.
Recently I looked at my small matches where AncestryDNA used its ‘Thrulines’ algorithm to show we both share common ancestors on our family tree and share DNA.
Fan chart showing the genetic ancestors identified by AncestryDNA using ThruLines for small matches 6 – 7 centimorgans (August 2020; Fan chart generated by DNA Painter)
I have 9 matches with shared common ancestors and shared DNA of 6 to 7cM. Of these matches 8 also share DNA with my father. The 9th match has a strong genealogical connection on my Mainwaring line and I do not doubt we are 5th cousins. However, he does not show up among my father’s DNA matches so despite being cousins we do not share DNA. It is estimated that only one third of fifth cousins share DNA.
It may be that the match with my father was somehow modified by AncestryDNA’s proprietary Timber algorithm, which tries to eliminate false matches “because they are of the same ethnicity or population — meaning that they (and many others from that same population) share DNA that they inherited from a distant ancestor who lived much longer ago”.
The Timber algorithm removes matches where the segments show “identical DNA with thousands of other people at that particular place”.
Recording notes about matches in the AncestryDNA database
AncestryDNA allows users to make personal notes in their database for each of their matches. Users can record when they messaged a match, how they believe they might be related, and the details of their shared match.
part of the list of AncestryDNA matches. Those in the list where AncestryDNA’s Thrulines algorithm have identified a common ancestor are shown with a green leaf in the 3rd column – see orange arrows. Part of the notes field appears in the 4th column see green arrows.One of my DNA matches showing my notes about the match
I looked at the 38 matches in the range of 6 to 7 cM shared DNA where I had made notes.
Of these 38 matches only one was shared with my mother, who shares 9 cM with that match. I don’t know how we connect.
Of 19 matches for which I had made notes and messaged, the matches also recorded shared DNA with my father. Three show common ancestors. Sixteen do not show common ancestors at present, although for several I know definitely how we are related.
Eighteen matches that I had annotated do not show as sharing DNA with either of my parents. It is thus likely that these matches and I do not share a common ancestor who can be genealogically traced.
Two of these matches had previously shown up as common ancestors, a green leaf in the list and the connection between our trees identified but no longer show up with the connection between our trees. Moreover they do not share DNA with my father.
For 2 of the 18 matches my father does not show as sharing DNA but does share DNA with another relative administered by the same manager. To me this indicates a possibility that the match is genuine but AncestryDNA’s Timber algorithm has modified my father’s match so it does not show up.
Consequences
I am not concerned if AncestryDNA removes smaller matches from my match list. Based on my very small review I accept that around half of the matches do not share DNA with my parents and thus are not useful matches for genealogy.
Of the remaining matches I already try to make connections with cousins who are researching the same ancestors using Ancestry.com’s member connect facility, which helps users to find fellow users researching the same ancestor. So while the ‘Thrulines’ method of highlighting shared DNA and common ancestors on a tree is useful, it is not the only means to make connections with cousins.
The Member Connect option is highlighted by the orange arrowWhen you click through to Member Connect you can see other people who are researching the same ancestor, the facts they have used and the Ancestry.com sources they have saved to their tree. Sometimes Ancestry.com does not correctly identify the common ancestor and you can ignore their suggestion.
Other matching services
Databases such as MyHeritage, FTDNA, and GEDMatch have tools that AncestryDNA does not provide. The tools are based on a chromosome browser, which helps to reveal details about the matched segment, enabling users to compare the shared segment with other matches. Without this it is impossible to be confident that the inherited segment is indeed from a distant ancestor. (See my post on Triangulating Matilda’s DNA.)
These other matching services have databases considerably smaller than that of AncestryDNA. Notwithstanding the better tools they have and the ability to see details of shared segments, I think it is best to test at AncestryDNA in the first instance because of the larger pool of matches.
Estimate of the size of the major autosomal databases in January 2020 caculated by Leah Larkin and published at https://thednageek.com/autosomal-dna-database-growth/ In January 2020 AncestryDNA announced it had past the 16 million mark; in July 2020 AncestryDNA announced it had passed 18 million tests. When we first tested in July 2016 the AncestryDNA database was less than one sixth the size.
Conclusion
The findings that a significant proportion of DNA matches are not genealogically significant seems plausible . For those small matches that are in fact genealogically sound I am prepared to miss out on these and concentrate my research efforts on the many thousands of larger DNA matches where I can be confident that there is definitely shared DNA and a genealogical connection if I could work it out – there are plenty of puzzles yet to be solved.
I will be pleased if AncestryDNA’s decision to remove small matches relieves pressure on its computing resources and improves response time for its users.
How will these proposed changes affect subscribers? I hope that AncestryDNA will provide more information about shared matches and new tools for exploring DNA data. And I wouldn’t mind at all if I never saw the “backend services are overtaxed” message ever again.
Sources
AncestryDNA Matching White Paper Last updated July 15, 2020 – Discovering genetic matches across a massive, expanding genetic database
We share more and longer segments of DNA with our closer cousins, a fact that can be turned to use in family history research: find someone with whom you share a significantly long string of DNA and that person is your genealogical relative – you can probably work out how you are related.
Cousinship in the great tree of life means a common ancestor: whales and cows are related in this way. The DNA we share, or to be precise, the fact that we share it, provides clues about our relative places in the tree. To focus in a little, our relative places in the tree of our direct forebears and cousins are indicated by the segments of DNA we share. The more DNA I share with someone the more recent our common ancestry.
Last year I wrote about AncestryDNA’s ‘ethnicity estimates’ and ‘genetic communities’. AncestryDNA has two ways of looking at your genetic background: the ethnicity estimate which compares your DNA to a reference group and genetic communities where you are linked with cousins who share DNA from a similar geographic area.
AncestryDNA’s ethnicity estimate is intended to be a measure of a person’s ethnic makeup. Are you partly Inuit? Were your ancestors Tasmanian Aboriginals or Scottish Highlanders? AncestryDNA calculates the estimate using DNA data about people who, it is said “…have long-standing, documented roots in a specific area”. This group of people identified by the company provide a reference group for ethnicity estimates.
Genetic communities, compiled on the basis of shared DNA, are defined as “groups of AncestryDNA members who are most likely connected because they share fairly recent ancestors who came from the same region or culture.”
It is said that a large proportion of people who pay to become members of Ancestry do so in order to discover their ethnic makeup, and presumably many of them are satisfied with what they are told. Ethnicity is a tricky concept, however, and Ancestry’s pitch about ‘long-standing’ (how long?), ‘documented’ (by whom? how?) roots in a specific area (how is the area specified?) sharing ‘fairly recent’ (how recent?) ancestors (which?) in a ‘region’ (of what extent?) or culture (what’s that, for Heaven’s sake?), is a pitch that will strike many people as promoting something largely meaningless. [AncestryDNA explains some of this in their 2019 Whitepaper on ethnicity estimates but you can see for example that they are estimating Aboriginal and Torres Strait Islander ethnicity on the basis of 14 DNA samples only.]
In late July 2020 AncestryDNA updated its genetic communities calculations, including those for communities associated with European and British settlers in Australia. I have looked again at my family’s place in the ethnicity estimates and genetic communities provided by AncestryDNA. The updated AncestryDNA genetic communities of my husband Greg and of my father became more specific: no longer vaguely “Southern Australia British Settlers” my father is now part of the group “South Australian European and British Settlers” genetic community and Greg is linked to the “Victoria, Australia, European and British Settlers” genetic community. Our ethnicity estimates have not been updated.
My father’s AncestryDNA ethnicity estimate showing the link to the South Australian European and British Settlers genetic communityGreg’s AncestryDNA ethnicity estimate showing the link to the Victoria, Australia, European and British Settlers genetic community
As I type these notes my cat Vinnie is sitting on my desk amusing himself by pressssssssssssssssssing randommmmmmmmm keys. I moved his paws, but now he’s taken to making sarcastic comments, and it’s hard to concentrate.
ME: “Most of Greg’s forebears came to the Colony of Victoria at the time of the gold-rushes and the assignment of this genetic community makes sense. AncestryDNA provides the information that just over 127,000 AncestryDNA members are part of this genetic community.”
VINNIE: “I’d say that the vast majority of his forebears didn’t come to Victoria at all. Most of them saw out their days on the African savannah. I’d call this a genetic community of approximately 50 million. What AncestryDNA ‘provides’ is just gas.”
Three close cousins have also been assigned to this community – we know how we are related to these cousins.A timeline with a potted history links forebears – for the most part the linking is accurate, these forebears are all associated with Victoria.
VINNIE: “In the logic trade that’s called a reductio ad absurdum. AncestryDNA’s methods make the daughter the mother of the mother.”
ME: “This was an anomalous result”.
VINNIE: “Did you get your subscription back?”
My mother’s DNA results summary report from AncestryDNA in October 2019
ME: “In response to this assignment of genetic communities and while waiting for the update, I removed my results from AncestryDNA by updating my settings and choosing not to see my matches and by not being listed as a match. My strategy seems to have worked. In the latest update my mother is no longer assigned to any Australian genetic community.”
VINNIE: “If I remove myself from the veterinarian’s appointment list I will no longer be assigned to it as a cat and you won’t have to take me for my annual checkup. Great.”
My mother still has very few DNA matches on AncestryDNA; the only match where I know how we are related is to me and I am also the only match sharing more than 50 centimorgans – that is all other of my mother’s DNA matches are likely to be no closer than 3rd cousins.my mother’s ethnicity estimate as at August 2020
ME: “Ethnicity estimates including the assignment by AncestryDNA to genetic communities need to be treated like any other hint with caution but as a clue to one’s origins”
VINNIE: “It was thought that the One Eyed One Horned Flying Purple People Eater had to be treated with caution too, but he turned out to be harmless. There weren’t any purple people for him to eat. You needn’t be cautious about nonsense.
An Ahnentafel (German ‘ancestor board’) table assigns a unique number to each person.
On your own Ahnentafel chart you are number 1. In the previous generation your father is 2 and your mother is 3. Your father’s number is calculated by doubling yours; your mother’s number is one plus double yours.
This scheme continues up the generations. Your paternal grandparents are 4 and 5. Your maternal grandparents are 6 and 7. Men have even numbers; women odd.
My table starts with my children as number 1 and incorporates both my husband Greg’s forebears and mine.
I use Ahnentafel numbering to keep track of our Most Recent Common Ancestors (MRCA), ancestors we share with our DNA matches, provided, of course, that I have been able to establish what the genealogical relationship is.
The update of my Ahnentafel index made me think about our progress on the tree. The last time I reviewed our tree progress was March 2020. At 31 March 2020 my tree showed 344 of the possible 1023 forebears up to 10 generations of 7th great grandparents. I know all 32 of my children’s 3rd great grandparents and thus all 62 of their possible ancestors to that level. At the 4th great grandparent level I know 53 of their 64 possible 4th great grandparents.
Direct ancestors whose names I know are coloured; blanks represent those whose names are unknown to me. Chart generated by DNAPainter.
In the four months since March I haven’t made any progress in identifying more ancestors in these 10 generations, but I have made a little progress in the generations beyond, with two more 8th great grandparents, four 9th great grandparents, two 10th great grandparents, and two 11th great grandparents. Adam and Eve are coming up.
Generation
Ancestors identified
Tree completeness at this level
Parents
2 of 2
100%
Grandparents
4 of 4
100%
Great-Grandparents
8 of 8
100%
2nd-Great-Grandparents
16 of 16
100%
3rd-Great-Grandparents
32 of 32
100%
4th-Great-Grandparents
53 of 64
83%
5th-Great-Grandparents
72 of 128
56%
6th-Great-Grandparents
76 of 256
30%
7th-Great-Grandparents
80 of 512
16%
8th-Great-Grandparents
66 of 1024
6.45%
9th-Great-Grandparents
43 of 2048
2.10%
10th-Great-Grandparents
31 of 4096
0.76%
11th-Great-Grandparents
21 of 8192
0.26%
12th-Great-Grandparents
12 of 16384
0.07%
Tree completeness calculated by DNAPainter. There is limited pedigree collapse: 10 people appear twice as our children’s 3rd great grandparents John Way and Sarah Daw were cousins who married.
Our family tree, including indirect relatives, has grown from 10,481 people in March 2020 to 10,928 as at August 2020. It now has 17,204 records (previously 16,099), 2,238 images (previously 2,109), and 305 stories (previously 289). I have added 65 posts.
These statistics give me a quick measure of the progress I’ve made. There still a long way to go…
Shortly before GeneticAffairs was asked to stop offering the AutoCluster analyses that employed Ancestry data, I ran Greg’s AncestryDNA matches through their autoclustering tool. AncestryDNA allows you to gather the same information, but I and many other users found the organisation and visual presentation offered by GeneticAffairs very useful.
I was looking at one of the smaller clusters – cluster 21 on the chart – and the associated notes, when I noticed that there was a small family tree of 22 people attached to one of the matches. Looking at the tree I noticed the Bell surname, which matched what I knew of the rest of the cluster. There was also a match with the Darby surname. Although I did not recognise Henrietta, the Darby surname did seem to fit the tree of the other shared matches where I did know how we are related, namely the trees of my Sullivan cousins.
small tree from Greg’s DNA match with a clue linking the match to the Darby family
I contacted Greg’s second cousin LB on Facebook to share the discovery, saying, “I have had a look at the tree [of SK]. She has a Bell marrying a Darby. Her tree has no details but I ran Vic BDM and found two births and the marriage.”
I dithered a little but decided to order the marriage certificate. The image of a Victorian historical certificate costs $20, not cheap, but there’s only so much you can do with just indexes.
1868 marriage James Bell and Henrietta Darby
It was indeed our family. At Creswick on 4 October 1868 Creswick James Bell, a miner, aged 22, married Henrietta Bell, no occupation, aged 24. Both were living at Creswick. They were married by a Wesleyan minister. The witnesses were Alexander and Agnes Pavina [I am not completely confident I am reading this correctly]. Henrietta said she was born in County Down, Ireland and her parents were John N Darby Compositor and Matilda Mograge.
I didn’t have Henrietta on our tree. If she was 24 in 1868 then she was born in about 1844.
I believe she is the child born in New Zealand, one of the two children of John Darby and his wife recorded on the shipping list of the Sir John Franklin, which left Auckland on 12 April 1845 and reached Hobart after what was described as ‘a tedious voyage of 25 days’. The other child was Matilda, who was baptised in Hobart in November 1845. She was born on 14 March 1845, less than a month before they set sail.
shipping list Sir John Franklin 12 April 1845
I had previously found no other record for the other child of John and Matilda Darby and had assumed it had died young.
I do not know why Henrieta said she was born in Ireland. Her parents were from Exeter, England and I am reasonably confident (if she recorded her age correctly) that she was born in New Zealand. Otherwise she was born in Australia. I ordered her death certificate which said she was born in Geelong and had lived all her life in Victoria. In 1896 her age was given as 47, which means she was born about 1849.
1896 death certificate Henrietta Bell
When John Darby married Catherine Murphy in Portland in 1855 he stated that his wife was dead and that he was the father of two children, one of whom had died. In fact, his wife Matilda was still alive and his second marriage was bigamous. I had assumed the living child was his daughter Matilda and that the unnamed child on the voyage had died. I now think that when John and Matilda Darby separated they kept a child each. Matilda junior stayed with her mother and Henrietta remained with her father, hence her knowledge of his name and occupation when she married. Her sister Matilda did not know her father’s name when she married William Sullivan in 1862.
Name John Darby Spouse Name Catherine Murphy Registration Place Victoria Registration Year 1855 Registration Number 2765
Henrietta and James Bell had five children before James’s untimely death in 1884:
Annie Jane Bell 1872–1918
Agnes Estella Bell 1875–1961
Catherine Elizabeth Bell 1878–1929
James Henry William Bell 1879–1928
Francis Sinclair Bell 1881–1935
Greg and his cousins share DNA with descendants of Annie and James Henry.
There were several Bell families in Creswick. The family trees I have looked at have different parents and a different death date for James Henry Bell, whose birth was registered as James William Bell. To confirm my suspicion that he was indeed related to Henrietta Darby I ordered his death certificate, and yes, James Henry Bell who in 1904 married Edith Jane Hocking (1884 – 1963) was indeed the son of James Bell and Henrietta nee Darby. I was thus able to resolve several more DNA matches that had puzzled me for some years. James Henry and Edith had seven children. He served in World War I, was wounded and was a prisoner of war.
1928 death certificate James Henry Bell
Yesterday we visited Creswick Cemetery and Long Point. Henrietta and James Bell’s grave is unmarked. Long Point, where they lived, is a pretty area of bushland next to a small settlement just outside Creswick.
Creswick Cemetery Methodist section row 13Long Point bushland reserve near Creswick
There are still unanswered questions about what became of John Narroway Darby and what Henrietta did before her marriage and how she came to be in Creswick.
I am pleased to have learned a little more about the family though. It’s fun to follow through the clues.
I was especially interested in the number of forebears I could name in the previous ten generations, that is, up to and including seventh great grandparents. The possible maximum, if you include yourself, is 1,023 individuals. [Cousins sometimes marry, so there might be duplicates, which in practice could reduce the actual number considerably.]
Looking at our tree from our children’s perspective the figure was then 31%, 319 of the possible 1,023 forebears.
As of 31 March 2020 my tree shows 344 of the possible 1023 forebears, 25 more. This just is 33.6%, slow progress of 2% over nearly two years.
Direct ancestors whose names I know are coloured; blanks represent those whose names are unknown to me.
These numbers of course don’t show all we’ve learned about our forebears and their relatives. I have done a great amount of research about the lives of people in our tree. Moreover, our family tree including indirect relatives has grown by almost half again, from around 6,000 people to 10,481 people.
The large increase is mainly due to my adding genetic cousins to the tree, among these many descendants of my forebears. I try to verify all connections. Our tree on ancestry.com now includes 16,099 records, 2,109 images, and 289 stories.
Not all of the forebears in our tree have associated genetic cousins. Some cousins have not tested their DNA. Some have tested but I have been unable to verify the connection.
Even for the cousins where I have found a connection, the shared DNA is not necessarily attributable to a particular ancestor. [There are ways of developing confidence about these attributions, some of which I described in my account of the triangulation technique I used to verify that Matilda Sullivan formerly Hughes née Darby was the mother of Henry Sullivan.
I have made the least progress on my German forebears. My mother very kindly submitted her DNA for analysis, but dissappointly, I have made no connections through her DNA. She has very few cousins and they are not close: her father was an only child, and her mother’s siblings had no children. DNA testing is not popular in Germany. On the AncestryDNA site my mother has only 27 4th cousins or closer and 12,882 matches in total; her closest match shares only 50 centimorgans. By contrast my father has 358 matches of 4th cousin or closer, his closest match shares 570 centimorgans, and he has a total of 43,912 matches on the AncestryDNA website. My suave and handsome husband Greg (editor of this online research journal) has 320 matches that are 4th cousin or closer, his closest match shares 1003 centimorgans, and he has a total of 31,875 matches on the AncestryDNA website.
On the MyHeritage website my mother has 2,035 DNA matches and her closest match shares 39 centimorgans. My father has 10,244 matches and shares 777 centimorgans with his closest match. Greg has 5,976 matches and his closest match shares 1,035 centimorgans of DNA.
On Greg’s side of the family – the left hand side of the fan – I have still to make progress on his Young, Cross, Sullivan and Morley forebears.
There is still lots of work to be done in identifying the relationships with genetic cousins, building the tree, and filling in the family history.
Not everyone would agree that artificially colourised photographs are better than black-and-white photographs. Perhaps it depends on the photo.
What do you think?
Here are some of the photos in my collection that have been colourised with the new tool.
My grandmother wrote on the back of the photograph that it was taken in 1908 and the names: Back row, left to right: Queenie Magee; Kate Cudmore; Nellie Millet Middle row, L to R: Eva Gedge; May Gillett Front centre: Kiddie Bennett
colourised picture of Cavenagh-Mainwaring daughters 1908 using the MyHeritage color tool
My great grandmother, Kathleen Mary Cudmore formerly Cavenagh-Mainwaring née Cavenagh, and her sisters in about 1908. I wrote about them at N is for Naval husbands.
Hans Boltz is sitting in the 4th row 2nd from the right wearing a sailor suit
Hans Boltz school about 1919 Photo colourised using the MyHeritage photo colorisation tool
The school in about 1919 of my grandfather, Hans Boltz (1910 – 1992)
Hans is younger in this photograph than with his classmates above
Hans Boltz as a child, photo colourised using the MyHeritage photo colourisation tool
John Young with his step children Bob and Mary Whiteman and his sons Jack and Cecil Young. Photograph taken 1898-9. A copy of this photograph came from the Tunks family (relatives on the Young side) but a copy is also held by the Way family (relatives of the children’s mother).
John Young, his two sons Cecil and Jack, and his two step-children Bob and Mary Ann Whiteman. Photo colourised using the MyHeritage photo tool
A photograph taken about 1899 of Greg’s great grandfather John Young (1856 – 1928) with Greg’s grandfather Cecil (1898 – 1975), Jack Young (1896 – 1918), and John’s two step-children Bob (1883 – 1957) and Mary Whiteman (1884 – 1945). I wrote about this photo at Y is for Young family photographs.
