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General => Ancestral Family Tree DNA Testing => Topic started by: Matriach on Saturday 06 November 21 15:46 GMT (UK)
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Hi everyone
My daughter has recently tested with a view to knocking down a few brickwalls in her scottish ancestry. She had a couple of matches from New Zealanders, who when contacted turned out to be half siblings(same scottish father). However there was a large difference in the Cm connection (62 and 230) with one described as a 4/6th cousin and the other a 2/3rd cousin. Is there a simple explanation for this?
Another puzzle - Ancestry says her ancestors are from the east coast (Banff and Buchan) - no mention of Ayrshire or the SW area where her father's family have lived since 1798 - and from where the majority of her matches originate.
I realise that the permutations must be great , but strange nevertheless.
Cheers, Matriach
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https://genetics.thetech.org/ask-a-geneticist/range-shared-dna-between-relatives
This is not something I understand myself, but this seems like a good explanation.
A grandparent/grandchild can have a 12.5-33.8% (centimorgan) range and half-siblings can range from 11.2-30.4%. Your 16% is reasonable with any of them!
All of this is one reason that the relationship a company assigns you should be taken with a grain of salt. They are doing the best they can with the data but there is a lot of slop in assigning relationships.
For example, my half-sister and I came out embarrassingly as grandfather/granddaughter. This makes some sense as both sets of relatives share around 25% of their DNA. But we could also have easily been called as uncle/niece.
And my example is with DNA that fits closely with the average amount these relatives share. Yours is even trickier.
The 16% is actually between an uncle/nephew and first cousins meaning either could be right. Or of course neither could be right too. This is why it is sometimes important to include other data or relatives to confirm a relationship.