A New Lot of DNA Test Results – Endogamy

Image from 'A Text-Book of Inorganic Chemistry' by G S Newth,Longmans Green and Co London, 1902 Figure 44 page 209
‘A Text-Book of Inorganic Chemistry’ by G S Newth,Longmans Green and Co London, 1902 Figure 44 page 209

Endogamy is the dreaded word for genetic genealogists.   Perhaps not the only one, but definitely up there as one of the greatest obstacles to solving the family tree puzzle.

It’s traditional usage is in reference to small populations who married each other and excluded outsiders.  This happened for cultural and economic reasons, thus you see the Royal Families of past Europe marrying each other to cement alliances and protect assets, or the English plantations in Ireland only marrying into their fellow planter families.  The result is cousins marrying cousins, uncles marrying nieces, second and third cousins marrying each other.  Four or five generations on the tree is a tangled web of interrelations.

This tangled state is called pedigree collapse – where instead of eight great grandparents someone has four or six due to the cousin marriages.

Obviously this means there is less genetic material to go round.  If cousins marry, their recombined DNA still looks a lot like the grandparents’ DNA because each parent had inherited identical segments.  That’s all they had to pass down.

What this can mean to a modern, living DNA test subject, is that they could have inherited DNA from one ancestor through both their father and their mother.  It’s hard to pick sometimes.

You really find out what is going on when you test your parents.

Currently in South Australia, we have had a week of fires and heatwave and are now on a flood alert.  Hence, I haven’t had much time to look at this new DNA test.  But of course I’ve sneaked a few minutes!  It’s very exciting.  There I was thinking my mother’s DNA would show me who was on which side of the family.  For some matches, it has done this.

I had four 2nd-4th cousin matches.  I’ve blogged about this.  Two adoptees, one McLeod cousin and one non-responder. I now know that one adoptee is on my father’s side.   The non-responder is on my mother’s side and the McLeod cousin is on my mother’s side.  No surprise with that one.

The other adoptee is on both sides.  In fact, she is a stronger match for me than she is for my parents.  She matches one segment from each and I have inherited both those segments. This makes me wonder about the status of many of my other matches.

I didn’t see that coming.  I’m looking in the wrong ancestor distance for our match.

What’s more, my mother’s 2nd-4th cousin matches are not showing up for me at all!  Not even at the 5th-Remote level.

This is a quick post just because I don’t want to get too far behind. My father’s test will be through any day.  For a short time, being very tired from heat and a constant level of emergency, I felt very disheartened.  But I have now bounced back.

Once the flood event is over, I’ll sort the whole mess out!

The elderly surviving members of one Dillon family of ten children.
The elderly surviving members of one Dillon family of ten children.
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