mt-DNA ~ Pedigree Collapse AND collapse over folks mistakes in understanding DNA

Oh, I could cry, I could have… a collapsing illness over the mistakes I saw in a video about two lovely doppelgangers taking DNA tests.

Long story short, they look remarkably alike, which we see in genealogy all the time, but when they use DNA to answer three questions about how closely they might be related, they are told no, they have no common ancestor in the last 20,000 years or so. And they know this because they have different mt-DNA haplogroups? Oh, I will hyper-ventilate.

In the video, they open three envelopes containing the answers to their three questions. The first says no, they are not full sisters and the second says no, they are not half-sisters. The second answer, if it is correct, could only have been determined with an autosomal DNA test.

It is with envelope number three, which says they are not related at all, that the story falls apart. This was supposedly determined with an mt-DNA test, but mt-DNA cannot tell you that. Certainly the autosomal test would have told them if any amount of DNA was shared, and maybe it did. Maybe this is just a case where the autosomal test showed that not only did they not share enough DNA to be full or half sister – they shared no autosomal DNA at all.

But to then jump from full or half siblings and say not related for X 1,000s of years means they do not understand their results.

1 chart all dna crest 2019

This is a loose representation of what the main three tests show. The y-DNA is MEN only. It only shows the single genetic line of the father’s father’s father’s father’s father’s and on and on. Not those father’s other family – not the father’s mother’s father – only the single blue line for MEN ONLY. The red line is the mother line the maternal DNA and we all have that, both men and women. The yellow is showing that the autosomal DNA is scattered throughout one’s genetic ancestry. We do not have genes – readable genes – to come down to us from every ancestor. So this autosomal test is perfect for parents/children, siblings, 2st and 2nd cousin perfect. There is still not a know case of 2nd cousins not matching. From 3rd cousin, it is all bets off – it can miss one siblings and catch another. With my 4th cousins 1r, I share 170 cMs with one sibling and I share 240 cMs with the other siblings.

The mt-DNA cannot tell any two people that they are not related anytime in the last any number of thousands of years. It can only tell you that you are not related on the single genetic line of your mother’s mother’s mother’s mother’s mother’s mother’s mother’s mother’s mother’s mother’s mother’s etc etc etc etc mother.

The above chart shows what the genetic mt-dna test covers. This single line of women. Not any of the spouses of that line. Not the mother’s father’s mother’s mother. Only the mother’s mother’s mother’s mother’s mother’s mother’s mother’s mother’s mother’s mother’s mother’s etc etc etc etc mother.

And it doesn’t show all of each mother – only the single strand of mt-DNA in this wonderful female, maternal line.

My mt-DNA haplogroup is H10a1. My paternal half sister’s mt-DNA haplogroup is W1 (we share about 1500 cMs [amounts of DNA shared]). My paternal 1st cousin’s mt-DNA haplogroup is H1ag1 and we share about 750 cMs ( H one of the most frequent haplogroups in Europe). My second cousin once removed is haplogroup U5a1 and we share 225 cMs. I have a 3rd cousin haplogroup H2a and we share 100 cMs. My 4th cousin is mt-DNA haplogroup J1c2 and we share 21 cMs. So having different haplogroup only means you are not related on your mt-DNA line until far back in time.

It is a mistake to say there is ‘no’ relationship. Because of pedigree collapse, there is.

There are enough misunderstandings in all of DNA without compounding them with fibs.

I would like to know if the two people shared any cMs at all. What was checked? Who was it they tested with?

In DNA for genealogy, or any genealogy, all teachers repeat over and over, do not go by what two people look like. When it works out it is wonderful but often it does not.

I have two people and they share no readable cMs, meaning any relationship is at least 3rd cousin or much further back in time. But their fathers match in y-DNA with zero mutations at 37 markers and they could have a common ancestor back in the distant past. The people look very much alike.

Because of pedigree collapse, any two people with European ancestry will quite likely share a common ancestor within the last 1,000 years.

Numbers of ancestors –

A person has 2 parents

4 grandparents

8 great grandparents

16, 32, 64, 128, 256, 512, 1,024, 2,048, 4,096, 8,192, 16,384, 32,768, 65,536, 131,072, 262,144, 524,288, 1,048,576, 2,097,152, 4,194,304, 8,388,608, 16,777,216, 134,217,728, 268,435,456, 536,870,912,

1,073,741,824 ancestors – one person has 1,073,741,824 ancestors – 30 generations ago – approximately 750 years ago.

There were not that many people on earth. All people have many of the same ancestors over and over again and we share those ancestors with literally millions of people.

So those two people in the video are related multiple ways within less than 1,000 years. But their question as remarkable doppelgangers OR 🙂 cousins is: Are they related within a frame of time that might account for their looks?

Based on what we were told in the video, they did not, I say again, did not say they were not related. They said they are not related based on their maternal DNA haplogroup, which means nothing.


If they tested with one of the companies that has the testing ability to tell them if they are related or not then they can download their raw data and then it can be compared “properly”.

Just try to get it a little bit right.

1ab Copy of 1 chart all dna crest 2019

Will they take the challenge and tell us if they got more information or will they compare their autosomal DNA and tell us.

These are the instructions to comparte raw data DNA at added sites.


Many have see the video where it seems they think they are not related based on their mt-DNA haplogroup. The haplogroup only tells us about one tiny piece of their DNA. They might not be related at all, but besides the mt-DNA there are many many other ways that two people could be related besides their maternal DNA.

It is a fun and exciting video but – I still wait for the answer. Do they share any X DNA? Any centimorgans at all? The 93 to 1 chance for a half sib does that mean they shared something? If so did they see matches in common?


2 thoughts on “mt-DNA ~ Pedigree Collapse AND collapse over folks mistakes in understanding DNA

  1. I agree.

    It’s funny mention the looks thing as that is a point I make in DNA presentations. It was about 20 years ago, a stranger came up to me, shook my hand, and asked how I was doing. Turns out I was a dead ringer for a close friend of his who works at a local mall. I forgot to look the guy up, but if a close friend of his could mistake us, that’s a great case for not relying on looks.

    Will re-blog this if you don’t mind.


    • It is always so tempting to look at the pictures of people we are trying to match up. I still do this first thing, I must! And I will always look. But I try not to get into the trap of going down one road and missing the right folks. I write these to help. For ages I sent private answers in emails and thought I should spread the hints and helps around. I would be thrilled if you shared, thank you for your approval!


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