4th Cousins on Ancestry.com: a quick study

 

Last week in the “Genetic Genealogy Tips & Techniques” group on Facebook, Blaine Bettinger posted a study of his own 4th-cousins-and-closer matches on Ancestry.com which can be viewed here.   I decided to do the same.  These are my results:

Cathy’s 4th cousin (and closer) matches on Ancestry.com

Matches which are included here are matches who, in general, share at least 20 cM of DNA with me (although I have some matches at the 20 cM level who are labeled as “distant” cousins).

The “Amt DNA” information does NOT come from Ancestry; it comes from having done a process called “chromosome mapping” or “visual phasing” and it required the DNA results from both my parents, as well as from my sibs, compared against that of my 1st and 2nd cousins who have tested. On my dad’s side, the amount shared skews towards my grandmother, in part because one of my X chromosomes comes from her and her alone.

The number of matches sharing >= 50 cM with me also skews towards my paternal grandmother because 2 of my dad’s 3 maternal 1st cousins have tested at Ancestry, as well as some of their children and grandchildren. All are no more distant than 2C1R to me. (Note: in that figure I do not include my dad, my sibling, or my paternal 1st cousins — since they share both paternal grandparents with me.)

However, in total numbers of matches, my two grandparents with “colonial” ancestry (and by that I mean roots in the U.S. at least as early as 1790 — but not necessarily as far back as, say, 1650), are the ones with the most matches. That seems to correlate with what I’ve heard from others who have tested at Ancestry. My paternal grandfather has one line — his maternal grandfather — that is “colonial”. My maternal grandmother has 2 lines — both of her maternal grandparents are “colonial”.

I compared the paternal and maternal labeling, but it doesn’t tell me much, in my opinion. Ancestry only labels the DNA match as paternal or maternal if the match is >= 20 cM for both parent and child. Where there are differences in the totals, it is due to the match being >= 20 cM for me, but not for my parent. That’s an artifact of the computer algorithms.

Finally, tree availability in and of itself may not be the be-all end-all for matches. 85% of the matches I identify as paternal unknowns — I cannot discern which grandparent they are kin to — have public trees. The trees have done nothing to help me figure out how that match is related to me! Any suggestions?

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