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The Search (2013-2015)

What did searching for a biological father look like in 2013?  Back then, you needed two things: DNA matches and a chromosome browser.

A chromosome browser (in case you missed the description in a previous post) is an application that illustrates all 23 pairs of your chromosomes.  The idea is this: when you DNA match someone, you need to see where the segments of your shared DNA are located on your chromosomes.  To draw a conclusion that you share a set of in-common ancestors, you need to find a third person that DNA matches you and another one of your DNA matches in the exact same location on your chromosomes.  Matching DNA segments in the exact same location on chromosomes, between at least three people was of utmost importance back then.  This is called, “segment triangulation.”

Segment triangulation is an assurance that it’s safe to assume that you and your other two DNA matches share an ancestor or an ancestor couple and that all of you inherited the same shared segment from them.  If you and the other two DNA matches all matched one another, it didn’t mean anything if you weren’t sharing the same segments.   The shared DNA segments were required to stack up and overlap one another.  One, two, three.   Each of the three segments on top of the others on a single, or if you’re lucky, multiple chromosome locations.  Next, you would compare family trees with these DNA matches,  find the common ancestors that your DNA matches share, build a family tree out and down from those ancestors to present day people until you sussed out a viable bio dad suspect, and voila!  Paternity solved.

Screen Shot 2017-10-26 at 2.38.38 AM

Two of my paternal cousins illustrating in yellow, a matching segment of DNA with me on a chromosome browser (they’re sisters).

I could tell you about using a matrix application, what constitutes a realistic amount of shared DNA to draw an inference, and what you can do to determine which side of your family a match comes from, but I’ll spare you all these painful details.  If you can understand the concept that other people share DNA with you, and that they got their DNA segments from the same ancestors you have, and that with chromosome browser you can see an illustration where this takes place on your chromosomes, and that to draw an inference of a shared ancestor they all need to stack up together on the same chromosome, you understand the concept of segment triangulation well enough.

Ancestry doesn’t have a chromosome browser.  So, in 2013-2015 I did most of my work at 23andMe, Family Tree DNA (FTDNA), and Gedmatch because these website do have one.  It was immensely helpful that I had tested my mom at 23andMe and had uploaded her raw DNA results to Gedmatch and FTDNA because with a mere click of my mouse, I could remove all the DNA matches I had with her and create lists of people only related to me from my mysterious biological father’s side.  I was at the ready to apply a laser like focus on these paternal matches.  And I did so, fruitlessly, for years.

The problem was none of my DNA matches were lining up perfectly on my chromosomes.  Oh, they all DNA matched me and each other, and I knew for certain that the connection was on my biological father side because they didn’t match my mother’s DNA, but looking at the shared segments on a chromosome browser, it didn’t look like perfectly stacked lines, each matching segment resting directly upon another; it looked like buckshot all over my chromosomes.  I had cousin Bob over on chromosome 12, cousin Sally on chromosome 4, and we all DNA matched each other on my paternal side but for the life of me, I couldn’t get these DNA matches to stack up and overlap one another on my chromosomes.  I thought at the time, if they weren’t lining up perfectly, that there wasn’t a single ancestor connection.  That it was utterly meaningless.

I was wrong.

Here’s why:  You share DNA in meaningful measure with all members of close family (your mom and dad, your siblings, your aunts, uncles, grandparents, great-grandparents, and everyone else up to your 2nd cousins) one-hundred percent of the time  Your 3rd cousins have roughly an 80% chance of sharing DNA with you and with 4th cousins, the statistic drops to only a 50% chance.  And it just gets less likely you’ll share any meaningful amount of DNA from there.

All I had were 4th cousin (and more distant) matches to work with.

But here’s the kicker…that 50% chance of sharing statistic is just about sharing any meaningful amount of DNA at all, anywhere on your chromosomes.   It has nothing to do with being able to triangulate shared segments with those 4th cousins.  In other words, you’re likely to share DNA with about half of your 4th cousins, originating from the same shared ancestor/ancestor couple, but whether or not you share DNA on the same exact location on your chromosomes with three or more of them is a whole other kettle of fish.  What’s that statistic of sharing matching segments with three 4th cousins?

About 1 in 1200, I’ve been told.

I don’t have 1200 paternal matches even now, five years in.

Questioning the other statistic, the one that tells me the chance of triangulating segments with a 4th cousins didn’t occur to me at the time.  I was taking it at face value that I should be able to triangulate segments with 4th cousins 50% of the time.  Of course, it wasn’t happening.  But I kept plodding on, every day, for years.  In the direction of nowhere.

This doesn’t mean that chromosome browsers are worthless.  They aren’t.  They can be extremely helpful in determining relationships.  In fact, they’re invaluable in some situations.  But every tool in the genetic genealogy tool kit has its limits and chromosome browsers are no different.  These days, despite the seemingly knee-jerk advice I see repeated endlessly to, “Upload to Gedmatch!” the vast majority of cases are being solved the way mine was ultimately solved: by building family trees for DNA matches.  On Ancestry. 

It’s 2017.  If you’re looking for a biological parent, you need to learn how to build trees.


Categories: Uncategorized

Laurie Pratt

Perpetually curious. I love history, genealogy, old movies, good books, all sorts of music, and adventures involving travel. In my spare time, I help admin a genetic genealogy Facebook page for CeCe Moore ("DNA Detectives") and coach people how to connect with their biological family using DNA.

2 replies

  1. I need the therapy as I am the one who really wants to find the bio father for my husband. This is become an obsession that I wouldn’t wish on anyone. I have a tree with mistakes. I have 2nd and 3rd cousins to him. Even met two cousins in California. But no closer to the truth.

    Liked by 1 person

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