Genetic Genealogy Guide

My cousin Hamish Maclaren has put together a primer on DNA testing for genealogy together with list of resources and guides to help you navigate the growing number of tests that are now available:

So what the heck is this DNA and family tree business?

DNA testing has become so pervasive in the last few years that there’s even a popular TV show in the US were celebrities get their DNA tested to find out more about their ancestors. And it is predicted that 90 million will have a genealogy related DNA test this year with numbers doubling every year for the past five years.

So how can this help us with genealogy?

Firstly, it is important to note that DNA tests can’t do your genealogy for you. What they do is help you connect to relatives who may help you find ancestors if they’ve added them to the family trees they have been working on.

Another limitations is that regardless of which test you take, the company behind it only only checks your results against others who have done their test. Unfortunately, there is not some big database somewhere where all DNA tests have been compiled so they can be compared. But the huge increasing numbers of those taking tests is only going to rapidly increase the size of the databases. This will in turn will greatly improve the chances of finding matches with those who have already found more on your ancestors.

At the same time, there’s the constant refining the origins interpretations, i.e. where in the world your DNA has come from and how it got there over thousands of years. Most DNA testers give you some version of this, often including maps with the lines of how your ancestors migrated from one place to another (more on this below in sections about Male and Female lines).

In my case, DNA matches have helped me find four more generations of ancestors of one paternal great great grandmother, and over a hundred related cousin in that line. I also found the parents and siblings of my paternal 3xgreat grandmother and so more cousins there.

And matches to my siblings and close cousins, have helped connect us with quite a few relatives on my mother’s side that we hadn’t known about previously, who kindly shared some great photos of our mutual great grandparents and their families.

And even with well documented families like my mother’s Birtwistle family, we continue to connect to close cousins not yet included on the extensive family tree we’ve been compiling (see more on Birtwistle family and tree collaboration here).

So in short, this DNA thing can work and be quite helpful

So where to start?

There are many companies offering DNA ancestry tests, so which one should you use?  Well, as always, it depends on what you want. Different tests test different things and prices vary. I am definitely no expert, but here are some thoughts based on my experience using a number of them.

Most of the time it make sense to start with a general test (what is called an Autosomal DNA test), which is good for about five-seven generations of all relations (see Notes on matches below).

When looking for the best one for this I looked at who had done the most tests, i.e. who had the biggest database of tests and family trees to check against.

Currently the two biggest DNA testers in this field seem to be Ancestry and 23andMe, but the last time I looked Ancestry’s database was significantly bigger. Also Ancestry has by far the largest collection of family trees in their database on line. So when you get a Match you can sometimes find their family tree and check that to see where you connect and possible find new ancestors.

The Ancestry test is usually about $99, but they seem to have sales every conceivable holiday. Their test (and 23andme) is a general Autosomal DNA test which is good for about five-seven generations.

Not only does Ancestry seems to the biggest family tree related DNA database. They also have by far the most family trees (over 100 million in 2019) to check against. An article from February 2019 showed that Ancestry had sent out 14 million tests, the next closest, 23andMe, had 9 million. The numbers are much a higher now. As yet, FamilySearch do not do DNA tests as far as I know, even if they may have more users.

The downside with Ancestry and 23andme is they won’t take anyone else’s test. However, if you download either of their test results you can upload them at no cost to FamilyTreeDNA, My Heritage and GEDMatch, if you create a free account with them. Those sites all have databases of more people who have done the tests and I would recommend doing that. I have done that with all of them and the Gedmatch was the one that led to finding about more about my 2 and 3x great grandmothers and their descendents.

To give you an idea I started with 23andme, then Ancestry, then did the mtDNA and YDNA with FamilyTreeDNA. Then uploaded the basic result from Ancestry to FamilyTreeDNA, My Heritage or GEDmatch. That was over a period of several years. At one point there were some issues with the compatibility of 23andme test, which I think have been resolved now.

I have also recently tried CRI Genetics, which in theory is better than the others for tracing more distant ancestors. But I didn’t find it gave anything much more useful to me than I already had from the other tests. I am note sure if CRI Genetics test results can be uploaded to FamilyTreeDNA, My Heritage or GEDmatch… yet.

What if you want to know about your male and female lines?

Female line

These needs the mtDNA (mitochondrial DNA) test. I did the FamilytreeDNA  mtDNA test. That shows the line of your mother’s, mother’s, mother’s, etc. And all the way back to the African Mitochondrial Eve over 150K years ago.

If you are non-African that would also go through the Out-of-Africa Eve about 80K years ago. If your female line is European, you would also see which of the so-called 7 Daughter of Eve you descend from – possibly as many as 18 now. This can help connect you together with relatives, who maybe also able to help you find out about ancestors and living relatives.

Mitochondrial Eve (aka mt-Eve or mt-MRCA) is the most recent common matrilineal ancestor (MRCA) of ALL living humans. In other words, she is defined as:

“…the most recent woman from whom all living humans descend in an unbroken line purely through their mothers and through the mothers of those mothers, back until all lines converge on one woman… As of 2013, estimates on the age of this split ranged at around 150,000 years ago, which is consistent with a date later than the speciation of Homo sapiens but earlier than the recent out-of-Africa dispersal.


Male Line

Finding out more about your paternal male lines needs the YDNA test. I used FamilyTreeDNA Big Y-700 test. As far as I know FamilyTreeDNA is the only one who does this, but there maybe others.  You could also do their Y-25 (I think), Y-35, and Y-111.

I found the Y-25 (or Y-35) produces a lot of not very useful matches. The best is the Big Y-700, but it is expensive at about $449 although they also have sales.

I found a dozen Maclarens who did match pretty closely, but so far we have no idea how many hundreds of years back. Again, as more people do the tests, the odds of getting more clarity will increase.

Basically, all these test go back to the African YDNA Adam.  AKA Y-chromosomal most recent common ancestor (Y-MRCA):

“He is the most recent male from whom all living humans are descended through an unbroken line of their male ancestors… As of 2015, estimates of the age of the Y-MRCA range around 200,000 to 300,000 years ago, roughly consistent with the emergence of anatomically modern humans.


Bringing this back to the Birtwistle (and other spellings) family tree collaboration, it would be great if more males did the Big Y-700, then we might be able to clarify if our origins are Celtic/Briton, Anglo-Saxon, Dane, Viking, Norman, etc.  Perhaps several people could get together to cover the cost of one relative doing it.

For entertainment, I have tried to put the lines of African YDNA Adam and Mitochondrial Eve all the way back to the Big Bang and the Multiverse. Going through all sorts of monkeys, mammals, reptiles, single cell organisms, the first molecule and atoms. etc. You can see more about this on here in Notes for Adam and Big Bang.

Notes on some of the challenges here:

In reality Neanderthals may not have bred with humans until they met out of Africa around 50-70,000 years ago. Perhaps it could have been with the “mother” of 7 daughters of Eve, although the “daughters” are thousands of years apart. Hopefully there was no extra marital infidelity, but who knows what was going on in those French caves!

Where and how to fit in Mitochondrial Eve and Y chromosome Adam is still a work in process, since they lived thousands of years apart. One can only hope they were somehow married and not “single parents”.

Then there is where to put the Biblical Adam and Eve? Particularly since some ancestral lines trace back through many biblical individuals to them.

Then where to put the date of the “creation”, around 6 pm on 22 October 4004BC, according to Archbishop James Ussher (or Usher; 1581 –1656) Primate of All Ireland. Or at nightfall near the autumnal equinox, but in the year 3929 BC, according to John Lightfoot (1602 –1675), Vice-Chancellor of the University of Cambridge. These were taken very seriously for some centuries and caused some problems for Darwin and others.

The above notes can also all be written off as a misguided attempt at humor.

Notes on matches

Because of way DNA recombines, every sibling has slightly different DNA (except identical twins). This means your test results might not show connections with some of your distant cousins matches. However, they might match with your siblings and parents. For example, my brother, sister and I each show connections with distant cousins the others don’t. The point being that the more of your family who take the test, the more relatives you can connect with and greater the chance that they will have new leads for you.

“About 10 percent of third cousins (who share the same great-great-grandparents) and 45 percent of fourth cousins (descendants of the same great-great-great-grandparents) have no DNA in common, says Drew Smith, a genealogical librarian at the University of South Florida in Tampa.” 

You can read more from this article about how siblings can have matches with different distant cousins, depending of which DNA bits they got from their parents.

Notes for hardcore DNA genealogists

For the hardcore types. There are a lot of different ways to further check where matches fit, like “triangulation”. I confess I have not tried that sort of thing yet, but a distant cousin did and found my 3xgreat grandmother’s parents and family. I think you can do that sort of thing with FamilyTreeDNA and GEDmatch, I am not sure about the others. There is lots of information online about doing that sort of thing.

Suggested reading for starting out:

3 Essential Tips You Must Know Before Buying a DNA Test. Your Free Guide to the Highest Rated DNA Tests” on Genetics Digest

I Have the Results of My Genetic Genealogy Test, Now What? from FamilyTreeDNA with Chapters from Matt Dexter and Blaine Bettinger (author of the popular The Genetic Genealogist blog)

Big Y-700 White Paper. Powering discovery in the field of paternal ancestry from FamilyTreeDNA co-authored by Caleb Davis, Michael Sager, Göran Runfeldt, Elliott Greenspan, Arjan Bormans, Bennett Greenspan, and Connie Bormans

FamilyTreeDNA also has a lot of useful information here.

The Ultimate Family Historians: Using DNA with Genealogy to make a great family history” blog by Linda Jones has very informative articles, although parts are far beyond where I am at for now.

There is a “Blog Archive” in the right hand channel with chronological links to articles, and sample of Linda’s articles including one on mtDNA here

You might also find these articles by Linda useful:

Breakthrough! Fabulous new tool for FTDNA Family Finder

(Remember you can import your Ancestry test results to FamilyTreeDNA which will appear under “Family Ancestry” Family Finder -Autosomal DNA)

What are the benefits of YFull?

The Big Y test from Family Tree DNA can knock your socks off! (also has lots of useful links to other articles)

How to make matches with Mitochondrial DNA (mtDNA)

There is also Family Finder Segment Triangulator:

The Triangulator is a Family Tree DNA web add-on that can triangulate autosomal DNA segments

Good luck with all that.


Below is a chart I found online that gives a rough idea at least how this aspect of DNA and family line thing works. I found several online, all slightly different but agreeing overall.

It shows how much DNA you have from different ancestors and which cousins will you share DNA with (and perhaps find someone who has done a tree of the line you are looking for, beyond where DNA can really help, as to my surprise I did with four more generations!).

The chart below might give you an idea. You are in the middle and the dark areas are the ancestors you still have DNA from, more or less.

Up to 2xgreat grandparents (the fifth row out) you should share some DNA with all their descendants. After that it goes downhill. The next row, your 3xgreat grandparents, some of their descendants will not share DNA with you. By the time you get to the outer row, your 5xgreat grandparents, it is a bloody disaster, you are going have DNA of very few of them, hence you share DNA with very few of their descendants.

However if I have understood correctly there is hope, each siblings (except identical twins) has different DNA and will share DNA with some different distant cousins and ancestors. So there is quite an advantage in having siblings, cousins, etc. do the DNA tests, to find different distant cousin (and see if anyone has done a family tree of a line you are looking for).

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