Has there ever been a series of triangulation tutorials starting from gen 1 and going upward exhaustively?

+25 votes
I am thinking about writing several separate topics on matching, triangulation, triangulation groups, and chromosome mapping. The idea is to be very specific and methodical in each tutorial. Rather than just giving vague instructions about how to handle the general process, I think it would be useful to lay out tutorials for each generation starting with the most recent and frequently the most well known and going from there.

So the first in my series would be triangulating your parents. Second in my series would be triangulating grandparents. I am not sure whether I would want to do triangulation of aunts/uncles, first cousins, and nth cousins m times removed as their own topics; I probably should.

I did a brief search to see if such a thing exists already, but I did not find the kind of thing I am looking for. Any interest?
asked Mar 20, 2017 in The Tree House by Ian Mclean G2G6 Mach 1 (11,680 points)
Sounds like an excellent idea. I would like to be able to triangulate 2 sibs & a 1st cousin, if possible. Everyone else is either deceased or wants nothing to do with DNA testing.
Hey Ian,

Nomenclature aside, can you send me something I can look over?

I am forking the document I am working on.

This version is the publicly editable document. I will be tracking the changes in both documents. And my feelings won't be hurt if people drastically change the tone, style, methods, standards, terminology, or pretty much anything in the document. Just try to keep it on the topic of the practical and theoretical methods of genetic genealogy.


2 Answers

+18 votes
Best answer
Hi Ian. I think a series of tutorials on matching is a good idea in general. But I wouldn't call parent/child matching triangulation. For triangulation you need an overlapping DNA segment shared by at least 3 DNA test takers. (For more, see this link to a blog post by Blaine Bettinger: http://thegeneticgenealogist.com/2016/06/19/a-triangulation-intervention/ )

Also, keep in mind that not all the cousins in the triangulation group need to be of the same degree. I have a triangulation group on gedmatch where my mom shares overlapping segments with a fourth cousin and fifth cousin twice removed. The segments are not an exact match at start and end points, but have significant overlap. (And, of course, the fourth cousin and fifth cousin match each other.)
answered Mar 20, 2017 by Janis Tomko G2G6 Mach 1 (16,130 points)
selected Mar 22, 2017 by William Foster
"But I wouldn't call parent/child matching triangulation. For triangulation you need an overlapping DNA segment shared by at least 3 DNA test takers."

I am very much aware of this, and it is one of the principle things I would be addressing in the "triangulating a parent" tutorial.

"Also, keep in mind that not all the cousins in the triangulation group need to be of the same degree."

I am also aware of this. The series I am thinking of would specifically be made to address this particular point. Triangulating parents is a fairly trivial procedure, but it is demonstrative of what is needed for triangulating and chromosome mapping more distant ancestors; I don't think that the community in general has a quantitative or intuitive sense about what is required to triangulate a nth generation ancestor; it is a practical necessity to use matches from differing generations and differing degrees to triangulate distant ancestors. Just how many and what degrees is what the series would need to build towards.

Thank you for the reminders.
These tutorials sound like a wonderful idea to me.  I would enjoy reading these articles.

"Triangulating parents is a fairly trivial procedure"

Perhaps it is trivial to you, but for those of us who are just beginning this process not so.
Hi Ian. I believe that you are very knowledgeable in this area and didn't mean to imply otherwise. So please don't take this the wrong way. My "issue" is with the term "triangulating parents." I think that "matching" would be a better choice or perhaps "chromosome mapping" if your intent is to explain that a chromosome inherited from mom can have segments from mom's dad as well segments from mom's mom. Triangulation has a more specific meaning than matching and it may ultimately add to the confusion to use the terms interchangeably.

That being said, I really do think your plan for a series of tutorials is a great idea and would obviously be very much appreciated.
I didn't mean to imply that matching child/parents is interchangeable with triangulation with parents. "Matching" and "triangulation" are different terms for different processes and should not generally be used interchangeably. The tutorials series would be properly about triangulation which depends on the basic process of matching but is distinctly different from it. I'll be sure to emphasize the difference between matching and triangulation.
+11 votes
Yes, please do! I have yet to be able to figure out the whole triangulation thing. I have read article after article to no avail, it is about as clear as mud to me. I would like to learn more about DNA and genetic genealogy.

Thank you for offering to do a step-by-step guide. I am sure it will help numerous people like me. Pictures would be nice too.
answered Mar 21, 2017 by Loretta Corbin G2G6 Mach 2 (25,530 points)
In addition to what Loretta has said, I add the following with the sincerest of good intentions... I hope it comes across that way.

I would recommend trying to keep things in plain language that most everyone can understand.  Try to follow the KISS Rule (Keep It Simple.... ) because not everyone is a geneticist. It's obvious that you and many others are very smart when it comes to Genetic Genealogy, but there are many of us out here whose eyes glaze over at the mere mention of centimorgans, double half 3rd cousins 10 times removed (what?), or other terms unique to this field.

Everyone is smart in what they know, but they are ignorant in what they don't know. As a former instructor, I know that everyone learns at a different rate, and that everyone doesn't come out of the box with the same knowledge base.  If they did, everything would be easy.  So please keep that in mind that everyone does not have a Doctorate in Genealogy when developing your tutorial. It's not about showing how much you know, but it's about sharing what you know with others.
I appreciate the advice. I do not have a doctorate of anything; I'm not actually even a college graduate. I have lifelong head, neck, and back injuries which greatly impair my ability to speak, think, and understand. Much of what I do and how I communicate is about coping with the errors systemic in my physical and psychological condition. I am not particularly smart either.

What I am is intensely curious and very stubborn; it is a family thing. I also dislike talking down to people or treating people like they're incapable of complex activities. Much of genetic genealogy or pretty much any scientific or artistic practice is tedious, banal, step-by-step reading and writing. It isn't difficult, but it is time consuming and often requires a lot of context. It helps to know the standard terminology that is employed by international organizations.

In any case, I have decided that I would like to try something given that people are stepping in with interest in what I am trying to write and with opinions about how it should be written.

I am drafting the tutorials in a Google document or documents. This link will allow anyone who uses it to comment upon the document; if you have a problem with the way it is written then please do make suggestions. https://docs.google.com/document/d/1Hrsu3fTj0JL38DPXZ12U7u5ygQmjhDBkwbxIBXz9DhY/edit?usp=sharing

I really like the idea of using google documents. I didn't even know this existed.... but what is a Karyotype? Perhaps you can include examples or links to examples?

Thank you for taking the time to share with those of us who want to learn about this exciting scientific practice and how to do it correctly. Personally, I can't even ask an intelligent question because I do not understand the terminology. And from what I have read so far, you have already enriched my knowledge. Keep up the good work.
I have updated the document with images and links.
Thank you Ian for doing this!!
Thank you, Ian. This is wonderful & clear --- and I also appreciate you acknowledging the diversity of human sex chromosomes!

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