ADSA and triangulation

For a very long time I have been avoiding triangulation with my mother’s matches for the simple fact that we lack documentation and how closely related we appear to be due to the lack of genetic diversity shared among Polynesian people.

I decided to once again try to make sense out of some of this by using dnagedcom.com’s Autosomal DNA Segment Analyzer, commonly known as ADSA.

A few months ago at one of our DNA Interest Group meetings we had Don Worth who developed this tool do a presentation.  He mentioned how those of Ashkenazi Jews or any endogamous group should increase the threshold to at least 10cM, in order to minimize the processing time.  At that time I still didn’t comprehend the reasoning and thought that it really wouldn’t matter.

Looking at just chromosome 11, this is what my mother’s results look like when I do not adjust the settings.

ch11-7cM

As you can see there are a lot of matches.  I knew that majority of Polynesians’ matches averages around 10cM with the largest segment.  When I increased it to 10cM, I get the following for the same chromosome.

ch11-10cM

So now it is reduced, I get less than what I would normally get, but there was a reason why I thought that increasing the threshold to 10cM for endogamous groups did not make sense to me before.   Although this is probably unique to Polynesians only compared to other endogamous groups, but the largest segment is not necessarily indicative of a closer match

The match with 13.76cM is a Maori while the others are Hawaiian.  There are two other people on that list at 12.35cM, a brother and sister who is actually much more distantly related to my mother (according to FTDNA) than the Maori person is.  That brother and sister’s father had a paternal grandmother that was Hawaiian, while their mother is Samoan.  The smaller total amount shared compared to others that share way more, is probably due to the semi-distant Hawaiian ancestress, or via their Samoan mother of whom is western Polynesian. Western Polynesians are older than eastern Polynesians, and eastern Polynesians are closer related to each other.  In other words, western Polynesians are much more diverse than eastern Polynesians.

There are other admixed Hawaiians of whom are not that close of a match to my mother, while there can be Maoris who are closer matches both having either large or small longest block/largest segment more than 10cM.  Therefore, increasing the threshold could possibly get rid of a lot of the Hawaiians of whom should be closer to my mother than the Maoris.  It seems to really matter too if the Polynesian is admixed or not.  Obviously the less admixed, the closer the relationship will show as far as the total shared is concerned.

Here is a look at the X chromosome with the minimum threshold increased to 10cM.  When I initially ran this with the default settings, the X results produced a very long list of matches.  Increasing it only managed to take out a few.

chX-10cM

Triangulation will still be a challenge for us.  The only thing that may be helpful is understanding that more multiple segments means the more interrelated you are, whether you come from multiple common ancestors or come from the same common ancestors multiple times.  The smaller the segments, the more distant the common ancestor(s) is/are.

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One thought on “ADSA and triangulation

  1. Pingback: Not all endogamy is the same | Hawaiian DNA

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