* Ancestry Changes

Got general Family History research questions - this is the place
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Sue036
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Re: Ancestry Changes

Post by Sue036 »

AdrianBruce wrote: 05 Aug 2020 21:24
Sue036 wrote: 05 Aug 2020 17:24... Before I repeat all my efforts for my 8cM matches, can you please advise whether you still think I might lose some of these from my list of matches at the end of August? ...
Ancestry now shows the decimal place for low matches so you'll see 7.9cM if you look now where you previously saw 8cM. So any 8cM matches that you see now will be 8.0 or above so will remain in the system.

You need to recheck - depending on when you did your previous checks - because some of the 7.9cM and below matches may have been 8cM when you last looked.

Hope this makes sense.
Yes, it makes sense, thanks.

I think that, in any case, I'll set aside some time to do another sweep through before the end of the month.
Sue in County Durham, UK

Researching numerous families but my current focus is on LE(E/A)D(H)AMs in Burton Upon Trent prior to 1829, thereafter in Stourbridge and also from c. 1865 in Sunderland and Newcastle Upon Tyne.
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gwilym'smum
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Re: Ancestry Changes

Post by gwilym'smum »

Adrian
Not sure if I am following you about DNA that you do not share with parents. On the DNA courses I have done it has been highlighted in capital letters that you cannot inherit DNA which your parents did not have. Those odd bits and pieces are what in simple terms they put down to DNA residual in the close knit communities and therefore not "family" . Is that what you mean by "chance"? Obviously I am not a scientist and I do think that people get taken in by the adverts that your ancestry will be revealed by taking a test and you will find all your lost cousins. DNA is a science and you need to understand how it works. The working with matches is hard work and is very time consuming.
I had never been contacted by any of my matches until recently when someone from MY Heritage contacted me with a 20 odd cm match. When I checked her match on Ancestry it was 6cm. She was very keen to find our common ancestor. I did do some work but could not find a place where the link would appear. She was very persistent until an online talk by Donna Rutherford who advised not to bother with very low matches. I commend her enthusiasm but I have more pressing research tasks to do. To work with matches it is better to work in collaboration but one problem is that not everyone has the same aims.
Stay safe and well
Ann
Researching Mayer, Parr/Parr, Simcock, Beech and all related families
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AdrianBruce
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Re: Ancestry Changes

Post by AdrianBruce »

gwilym'smum wrote: 08 Aug 2020 08:10 ... Not sure if I am following you about DNA that you do not share with parents. On the DNA courses I have done it has been highlighted in capital letters that you cannot inherit DNA which your parents did not have. ...
Oh gosh... Let me see if I can explain what's in my head. Every single bit of DNA that you have, did indeed come from your parents. But think about it, if you have siblings and you're not identical twins (and I think that there may be a rabbit hole of detail about what that means that I don't want to go down), then the two of you do not have exactly the same DNA. The string of DNA that you got from your mother is not identical to the string that your (theoretical) sibling got from your mother. If it were, you'd be identical twins.

The differences come from the fact that when your mother (or father) created the relevant egg (or sperm) there is a degree of shuffling that goes on in the DNA at that exact point in time. The DNA that's in the egg (or sperm) has all come from the parent - but it's no longer necessarily in the same order. (An analogy might be - "I'm playing all the right notes - just not necessarily in the right order!")

This shuffling is why we're not all identical twins and why our parents match someone in Ancestry DNA but we don't. It's also why we and our siblings won't have the same matches because matches are driven by that order. Of course, if the match that our parent has to someone is 100 cM say, then chipping a bit away won't make a lot of difference - the analysis will still see the match - it's just shorter for us.

Now think of a 5 cM segment in your parent's DNA. The mistake is to think that your version of that segment must always be shorter. It won't be - it's just different. And since there's only a limited number of letters in the DNA alphabet, it's perfectly possibly that the random change to that 5 cM segment actually results in a 7 cM segment that matches someone else who's totally unrelated to you since the Wars of the Roses. This sort of change results in a match that's regarded as being "Identical By Chance". You might think - but it's uncovered a common ancestor in the Wars of the Roses! Except that if you go that far back, or certainly to 1066, anyone with a substantial part of British descent is almost certainly related to everyone else with a substantial part of British descent - we don't need DNA to confirm that.
Adrian
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Mark1834
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Re: Ancestry Changes

Post by Mark1834 »

DNA is a science and you need to understand how it works.
That is an admirable aim, but one of the issues we have is that it is extremely complicated science, and a field that is still evolving (if you'll pardon the accidental pun). Even the basic building blocks are degree level biochemistry to understand properly, and the level it is presented in a typical family history context is a gross simplification of what is actually a very complex process. I strongly suspect that most tutors are simply passing on an empirical model, rather than having a deep understanding of the science involved.

To take a simple example - "what exactly is a centimorgan anyway?" It relates to similarity in DNA, and is an empirical measure of relationship. Take it a step further, and we bring in the chromosomes, but I think most of us would find it difficult to describe what it is from first principles.
Mark Draper
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