Author Topic: Ancestry DNA shared matches - bug?  (Read 3133 times)

Offline melba_schmelba

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Ancestry DNA shared matches - bug?
« on: Thursday 24 January 19 16:03 GMT (UK) »
Has anyone else noticed that quite often, when you click a match and then look at the shared matches, if you then click one of those shared matches, they will not show a match to the person you just clicked on and showed the other person as the shared match. Does this make any sense to anyone, or is it just yet another ancestry bug ::)?

Offline lisalisa

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Re: Ancestry DNA shared matches - bug?
« Reply #1 on: Thursday 24 January 19 19:39 GMT (UK) »
I haven't noticed it as such, and just tried with a couple of matches that were about 20cM's, and the shared match appeared.

I am still getting my head round 'shared matches' and the implications.  I notice that the shared matches list does not seem to include the more distant matches, 5th to 8th.  However I can click on a 5th to 8th match and get a list of shared matches.

Also the cM's shared shown are 'my results', so in the event that a shared person does then not appear on a list of shared matches of another match, could it be that although I match with say 20cM's or so,  the next shared match clicked does not include the earlier match perhaps because those 2 people have a lower cM's match, possible 5th to 8th, between each other?
Or am I looking at it in the wrong way?

I would probably have to find an example, know the numbers involved and possibly draw a diagram to try and work it out  ;D



Offline BristolClark

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Re: Ancestry DNA shared matches - bug?
« Reply #2 on: Thursday 24 January 19 19:42 GMT (UK) »
You're lucky. All I get is nothing along with a buffering circle.

Offline melba_schmelba

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Re: Ancestry DNA shared matches - bug?
« Reply #3 on: Thursday 24 January 19 20:19 GMT (UK) »
I haven't noticed it as such, and just tried with a couple of matches that were about 20cM's, and the shared match appeared.

I am still getting my head round 'shared matches' and the implications.  I notice that the shared matches list does not seem to include the more distant matches, 5th to 8th.  However I can click on a 5th to 8th match and get a list of shared matches.

Also the cM's shared shown are 'my results', so in the event that a shared person does then not appear on a list of shared matches of another match, could it be that although I match with say 20cM's or so,  the next shared match clicked does not include the earlier match perhaps because those 2 people have a lower cM's match, possible 5th to 8th, between each other?
Or am I looking at it in the wrong way?

I would probably have to find an example, know the numbers involved and possibly draw a diagram to try and work it out  ;D
I think you might be on to something here! Looking through my matches, there are no 5th-8th cousins in shared matches i.e. below 20 centimorgans, can't believe I haven't noticed this before! That is why when I click a 5th-8th cousin match, and click one of their shared matches above 20 centimorgans, they they don't show up as they are under 20. Why ancestry have made this decision to draw this seemingly arbitrary cut off point in shared matches when they do show them individually seems rather vexing and unhelpful to me, but I suppose there must be some rationale to it ???? This looks like one way GEDMATCH can allow a more in depth look than ancestry. I wonder if 23andme and myheritage have a similar limit?


Offline Gadget

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Re: Ancestry DNA shared matches - bug?
« Reply #4 on: Thursday 24 January 19 20:50 GMT (UK) »
I remember raising this a few months ago and Margaret confirmed that it was the lower confidence matches that disappear and reappear. I've tried to find the thread but so far I can't locate it.

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Offline melba_schmelba

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Re: Ancestry DNA shared matches - bug?
« Reply #5 on: Thursday 24 January 19 21:57 GMT (UK) »
I remember raising this a few months ago and Margaret confirmed that it was the lower confidence matches that disappear and reappear. I've tried to find the thread but so far I can't locate it.

Gadget
Was it this thread?
https://www.rootschat.com/forum/index.php?topic=794156.0
The DNA matches seem even more of a minefield than I had imagined. Apparently ancestry introduced a new system in 2015 called Timber that filters out segments, that are either very small or they think are from the distant past. But if you look at the comments a lot of people complained that this filtered out genuine matches that they have proven genealogically and find multiple matches between genealogically connected users on GEDMATCH.

https://blogs.ancestry.com/ancestry/2015/6/8/filtering-dna-matches-at-ancestrydna-with-timber/

(from https://isogg.org/wiki/Autosomal_DNA_match_thresholds)

Offline Gadget

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Re: Ancestry DNA shared matches - bug?
« Reply #6 on: Thursday 24 January 19 22:07 GMT (UK) »
No not that one but that seems odd too!

It was definitely one which showed some shared matches with distant matches (<20cM) but not if I tried the other way around.

I still can't find it. I don't think it was a thread that I started though  :-\

I had a very strange match coming up on Gedmatch Genesis yesterday. A 3rd cousin and I had exactly the same reading with a more distant relative. Exactly the same segment on chr 6

Gadget

Add -

3rd cousin and I share:
Largest segment 39.1/Total cM 124/

we both have the same results with the other match:
Largest segment 15/Total cM 15/
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Offline Rufous Treecreeper

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Re: Ancestry DNA shared matches - bug?
« Reply #7 on: Friday 25 January 19 00:08 GMT (UK) »
Thanks for the information  :)
I had noticed this happening too.
Cheers
Marlene
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Offline stevemiller

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Re: Ancestry DNA shared matches - bug?
« Reply #8 on: Friday 25 January 19 08:34 GMT (UK) »
Hello Gadget,

Were you thinking of this thread?
https://www.rootschat.com/forum/index.php?topic=801386.0

Page 2 has some mention of folk below 20 cMs not showing in shared matches.

Steve
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Hants- Hine/Hind
South Oxon- Applebee Barlow Clark Edginton Elliott Fryzer Simmonds Toby
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Surrey- Edwards Knight Lanaway
Sussex- English Exeter Jeffery Knight Mugridge
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