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View Full Version : Colonial inbreeding and its effects on my results



botoole60611
11-24-2012, 04:16 AM
When I started my DNA journey five years ago, I was an adoptee wondering about my genetic makeup. Thanks to a lot of circumstances, I know who both birth parents are and have about 4500 names in my family tree.

Plymouth colony on both sides. My bio-dad is 3/4 colonial - mostly Massachusetts and Connecticut; some Mayflowers and lots of folks pre 1650. My birth mother is 1/4 English colonial - Massachusetts, and also has about 20% Acadian lines.

What this means to me is that I have 140 DNA/paper matches (out of 800 sets of autosomnal matches) and the closest I have found is 7th generation common ancestors. One of my Acadian ancestor matches is a woman who shares 22 cM with me and our common ancestor was born about 1700.

When I started out learning about autosomnal and the rules of thumb about the amount ot DNA which would (normally) indicate 4th, 5th, 10th..., it threw me because I could not find closer connections, even after I found my birth parents and knew names through a lot of generations. A recent match was 10 cM and he had a good GED file. 10th cousins.

I manage the Massachusetts project on www.ancestor-projects.com. A new member just joined, and I checked his GED file against mine - we have an 11th GGF and a 9th GGF -> one is on my maternal side and the other is paternal. So inbreeding/inter-marriage, whatever you want to call it.

On the bright side, the DNA and paper match, and I am comfortable with that. And if I ever get off my butt and write the computer program I want, I may be able to see more results in terms of predicting where the match might be based on the chromosome location. Right now I can predict that a match in one chromosome area (for me chromosome 3) stands a good probability of Acadian ancestry - got 25 positives and 3 negatives in that clump.

But - the cousinship predictor forme on 23andME and FTDNA is out the window. I made all 219 matches on FTDNA 'distant', because they are.

Wing Genealogist
11-24-2012, 02:13 PM
With a single exception, my family has been in rural Maine since the beginning of the 19th Century and almost all of them descend from Great Migration Colonists, arriving in New England prior to 1650. As a result, my ancestry is very much inter-related. I just computed the relationships between my 16 great-great-grandparents and with a single exception, they are all related to one another (and NOT by marriage). In a few cases, I had to go back to the Middle Ages (and Nobility lines) but on average, my great-great-grandparents were 6th cousins (sometimes one generation removed) from each other.

In the vast majority of cases, they are cousins many times over, so the net effect is they are genetically even more closely related than the cousin-ship stated.

I have taken autosomal tests from 23andME and FTDNA and the relationships and agree the relationship predictors are worthless for my family. While at the recent FTDNA conference, I spoke with Elliott Greenspan about my issue, and challenged him to find a way to allow folks like myself some ability to add in a inter-relatedness coefficient to get somewhat better results. I won't hold my breath on this happening, but who knows??

EDIT: For anyone interested, you can find my ancestry online at: http://wc.rootsweb.ancestry.com/cgi-bin/igm.cgi?op=PED&db=rtwancestry&id=I1

botoole60611
11-24-2012, 11:27 PM
With a single exception, my family has been in rural Maine since the beginning of the 19th Century and almost all of them descend from Great Migration Colonists, arriving in New England prior to 1650. As a result, my ancestry is very much inter-related. I just computed the relationships between my 16 great-great-grandparents and with a single exception, they are all related to one another (and NOT by marriage). In a few cases, I had to go back to the Middle Ages (and Nobility lines) but on average, my great-great-grandparents were 6th cousins (sometimes one generation removed) from each other.

In the vast majority of cases, they are cousins many times over, so the net effect is they are genetically even more closely related than the cousin-ship stated.

I have taken autosomal tests from 23andME and FTDNA and the relationships and agree the relationship predictors are worthless for my family. While at the recent FTDNA conference, I spoke with Elliott Greenspan about my issue, and challenged him to find a way to allow folks like myself some ability to add in a inter-relatedness coefficient to get somewhat better results. I won't hold my breath on this happening, but who knows??

EDIT: For anyone interested, you can find my ancestry online at: http://wc.rootsweb.ancestry.com/cgi-bin/igm.cgi?op=PED&db=rtwancestry&id=I1
From past romps through GEDmatch.com, I know we share some DNA and I had John Perkins (1583) and Judith Gater as common ancestors. I had a problem with the GEDmatch review of GED files because of all the 'Living' and wasn't sure which was you to work a pedigree live to check against mine. Thomas Riggs is my 10th GGF. On my maternal side, my grandfather left Gloucester, MA, in the 1930's, but that line was there since Gloucester was founded.

My GED file is 1522518 and my kit number is FN57121.

Bart

Bart

Wing Genealogist
11-25-2012, 01:37 AM
From past romps through GEDmatch.com, I know we share some DNA and I had John Perkins (1583) and Judith Gater as common ancestors. I had a problem with the GEDmatch review of GED files because of all the 'Living' and wasn't sure which was you to work a pedigree live to check against mine. Thomas Riggs is my 10th GGF. On my maternal side, my grandfather left Gloucester, MA, in the 1930's, but that line was there since Gloucester was founded.

My GED file is 1522518 and my kit number is FN57121.

Bart

Part of what makes things so difficult (on my end) is the innumerable interrelationships. Not only do I descend from John Perkins (and his wife Judith Gater), I also descend from John's Uncles, Thomas & Isaac Perkins. Likewise, I have two lines of descent from Thomas Riggs of Gloucester.

My mother's parents were both from the same small, isolated town (Embden, Maine), and their ancestors all settled in the town circa 1800. For over 100 years they had little choice but to marry into the small community (as it was really too far to go a courting before the arrival of the automobiles in the 1940s). As a result, they have an infinite number of relationships to one another, starting with 3rd cousins.

Trying to figure out the exact degree of relationship becomes an impossible task, and even if it could be figured out, we would still be left not knowing exactly WHICH connection brought the common DNA down to me.

SC11
11-25-2012, 02:38 AM
I am partially Spanish New Mexican and find that the cousin predictor is most accurate with my matches who are also partially of the same ethnicity. The matches with those who are full blooded Spanish New Mexican have a cousin prediction that is almost always closer than the actual relationship on paper

Björnsson
09-11-2019, 07:40 PM
My own Yankee and Québecoise creole genealogy is a tangle of fishhooks, for my paternal grandmother and maternal grandfather both inbred from the same colonial gene pool, with first cousin marriages on each side and are also distant cousins, each paternally Yankee and Irish, maternally Québecoise. That's why they look like sister and brother in all my pictures, so I've wondered what it would have been like, if they married each other to begin with and made Mom. My father's father is Northumbrian on both sides and my mother's mother is Virginian on both sides, so it would've been interesting to see if they were to make Dad instead; instead of my parents' genealogy overlapping, I would freshly be such a blend in one generation and one individual. Unfortunately, Ancestry DNA only recognises my Virginian and Québecoise populations, completely overlooking my Yankee family tree, although they do get my British Isles regions. I'm an 11th great-grandson of Roger Williams, born and bred in Providence, RI. That's why I'm upset with that company. At least Living DNA gets my Northumbrian and Anglo-Saxon (Mercia-Wessex) subregional percentages accurate. I was surprised that East Anglian and Kentish are practically non-existent, considering 3/4 of my grandparents come from Home Counties families and 1/4 is of tested and proven Viking derivation.