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Ancestry Matches 7cM and less
- Thread starter Andrew Lloyd
- Start date
What I mean is that they are clearly in the middle of the update and things may have got out of sync.
Chris from Stansted
Genealogy in the Sunshine 2015
Comparing the longest AncestryDNA segment value with the shared cM value provided by Gedmatch for the same match, the two number are very similar value.
That makes sense, although remember that you can adjust the parameters at GEDmatch.
Helen7
LostCousins Superstar
I found the same, though the value for total shared DNA is always higher at GEDmatch.
I've done a similar exercise and found the vast majority of the single segment matches give a longest segment greater than the total shared segment, usually by around 1-5 cM but some much longer - my biggest discrepancy was shared DNA = 27cM, longest segment = 39cM.
Likewise. I have one of 31cM across 4 segments with longest segment 25cM, and another of 29cM across 2 segments with longest segment 29cM.
I can only assume, as Peter says, that these figures are out of sync as they don't make much sense as they are.
Chris from Stansted
Genealogy in the Sunshine 2015
Shared DNA: 20 cM across 1 segments
Longest Segment: 197 cM
Longest Segment: 197 cM
Chris from Stansted
Genealogy in the Sunshine 2015
Ancestry’s Timber algorithm, which tried to eliminate false matches, reduced the shared DNA segment match value for many of our matches. In 2016 the minimum reported value was reduced to 6cM, this is now being reduced to 8cM. Each of these steps has significantly reduced the number of our matches. Ancestry has acknowledged that many sub 8cM matches are genuine, They are throwing out the baby with the bath water. Now Ancestry needs to explain their definition of longest segment, it’s making no sense to many of us.
Just noticed this on notes connected to shared and longest segment information from ANCESTRY
In some cases, the length of the longest shared segment is greater than the total length of shared DNA. This is because we adjust the length of shared DNA to reflect DNA that is most likely shared from a recent ancestor. Sometimes, DNA can be shared for reasons other than recent ancestry, such as when two people share the same ethnicity or are from the same regions.
Pauline
LostCousins Megastar
I'm inclined to think, particularly with the somewhat bizarre example you give above, that something may have gone wrong with this new feature. Since Ancestry have been made aware of the situation, then the chances are things will be sorted in due course and we just need to be patient.
Pauline
LostCousins Megastar
Your post appeared just as I was posting mine, and from what you quoted it seems something may not have gone wrong after all, and that the length of the longest segment may sometimes seem bizarre.
Which leaves me wondering if the information has much practical use.
I can't believe how impatient everyone is. Can't we just wait and see what happens?
Ancestry has not really covered itself in glory - supposedly all that there is to go is for me to lose 65% of my matches (which I am fine with).
Doing the three changes over a month has only added to the agony as most people will not been saving any of the lost 6-8cM matches (from my own experience when advising others)
What most of us may be do not understand is how is these changes going to improve our understand of our DNA matches.
Most of my high cM matches I know how I am connected and knowing how many segments or the largest segment does not add any value (as I will not know which chromosome they apply to unless loaded on another website)
Most of the low cM matches are single segments and therefore the shared cM and longest segment should be the same or similar.
I can gain much more information about my Ancestry matches from DNAGedcom Client than is or will be available from Ancestry.
However I believe the biggest loss to Ancestry over the last year was the demise of DNA circles.
Pauline
LostCousins Megastar
How do you mean? Are you expecting something to happen?
Yes, I'm expecting the transition to be completed at some point in the next few weeks.
I was never in a single DNA Circle, nor were any of the tests I managed - I couldn't see what the point of them was, and nobody could tell me. By contrast ThruLines and, more recently, Common Ancestors, have delivered amazing results.
So long as Ancestry keep delivering great results I'm going to continue to assume that they know what they're doing. Anyone who needs to know more should read the White Paper.
jorghes
LostCousins Superstar
I agree with Peter - even though some of my results did appear in Circles, they didn't give you an idea of where you were linked with the individuals in the circle, and I had a few where it was telling me that the result belonged in the Circle, but couldn't give any ideas as to where that link might be as there weren't any shared ancestors in my tree that matched the relatives that the Circle was telling me the result belonged to.
ThruLines and Common Ancestors do that and more, particularly useful is the ability to show where you may be related.
Pauline
LostCousins Megastar
Yes, I’m well aware of that, but that wasn’t what I meant. How is it being impatient to be discussing the addition of the new longest segment information now? And are you saying that when the most distant matches disappear at the end of the month its practical usefulness (or otherwise) will become apparent?
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At the moment we have a situation where the longest shared segment displayed can exceed, sometimes by a very considerable margin, the total of all the shared segments - whilst we can speculate, it's impossible to know for sure whether the numbers we're seeing are meaningful or not.
Looking ahead, I can't say whether you will find the information useful, but I expect that I will. In the days when I used other DNA sites extensively I always sorted my matches by the length of the longest segment, and if they offer this option I'll probably do the same at Ancestry.
TerryM
LostCousins Member
Whilst I agree that Thrulines have been very successful, DNA circles would connect DNA results from cousins who did not match to you directly, but did match to someone else in the circle. Therefore the totals in DNA matches for any one common ancestor were higher than in Thrulines. This would allow a broader 'net' of descendants.
You can achieve something similar by giving reciprocal access to your DNA results to your cousins and then you can see how a potential match might link across different family lines. One of my brick walls is in the process of coming down because three different 4th cousins are showing links different links to a line which would be 6th cousins. Individually we would only have 2 or 3 matches to this line but grouped together we have many more matches and stronger proof.
Ancestry missed an opportunity to do something constructive with DNA circles - it could have created a community around each ancestor and used this to 'fix' the correct information for specific people - as agreed by each community. They could of then quarantined those trees which did not conform to accepted truths for prominent historical people and this would have benefited new members who match into those circles.
As it stands at present, you can find misleading information on Ancestry for even some of the most well researched historical figures like Mayflower passengers.
But at present both Thrulines and DNA circles (previously) will perpetuate mistakes from inaccurate trees - for instance creating extra children because someone has added a variation of their DOB. Experienced researchers see it immediately but beginners do not.