Genealogists use three kinds of DNA tests to trace family history and ethnicity:

— Autosomal (atDNA), the most popular, which analyzes the 22 base pairs of chromosomes inherited from both parents. This is the one used by Ancestry.com and other popular sites. While you get 50% DNA from each parent, which 50% you get is random. The atDNA test is only useful (right now) back to about five generations. Think of it as providing broad but somewhat shallow coverage.

— Y-Chromosome (Y-DNA), only for males, traces the direct paternal line, passing from father to son, generation after generation.

— Mitochondrial (mtDNA), traces the direct maternal line, for both men and women, passed down from mothers.

Providing narrow but deep tests of your family tree, both Y-DNA and mtDNA are passed down nearly unchanged, revealing ancient migratory patterns and the specific halpogroup — a genetic population group — from which your direct line originated thousands of years ago.

At some point I will likely devote another blog post to Y-DNA testing. In this post I’ll talk about the maternal line, and share with you the results of my own mtDNA testing.

Mitochondria

Mitochondria, the powerhouses of the cell, are passed down from your mother’s egg. Your father shared none of his mitochondria with you. All of a woman’s biological children inherit her mitochondria, but only her female children can pass it along to their children.

This is why none of us has mtDNA from our common Mattimore side. Our great grandparents, Henry B Mattimore and wife Mary O’Rourke only had sons Harry and Joseph. There were no females to carry forward the mtDNA from Mary O’Rourke and her maternal line. A mother who gives birth only to sons will see her mtDNA lineage lost.

Because mitochondrial DNA does not recombine — like autosomal does with DNA from both mother and father — it allows scientists to trace human ancestry way back to a common ancestor, “Mitochondrial Eve” (not to be confused with Biblical Eve).

All About Eve

Mitochondrial Eve represents the most recent common matrilineal ancestor of all living humans, estimated to have lived in Africa about 150,000–200,000 years ago. While her specific time estimate may adjust with more data, it is unlikely to “go back” much further in time to a different woman, as she represents the convergence point of all surviving maternal lineages.

 
• Why 150k–200k Years? This timeframe is based on the mutation rate of mitochondrial DNA. It is the most recent point where all maternal lines converge.
• Will it Go Further Back? The “Eve” we discuss is the most recent common ancestor. As time passes, some current, rarer maternal lines may die out, while others persist, which could eventually move the “most recent” common ancestor closer to the present, rather than further back.
• Not the Only Woman: Mitochondrial Eve was not the first woman or the only woman alive at the time. She is simply the only woman whose maternal lineage has remained unbroken to the present day. 

In other words, there were many women who came before this genetic Eve and many women who came after, but her genetic code is the point from which all modern branches on humanity’s family tree grew.

This is a really complex topic, and I don’t want to go any deeper into the weeds, so I shall leave it there. If you’d like to read more, here are a few links: here, here or here.

My Motherline
My own results, while not super helpful for my immediate genealogy research, are fascinating nonetheless. And just to reiterate, because mtDNA does not recombine, all of my siblings will have gotten the exact same mitochondrial DNA from my mom that I did. But aside from my siblings, each of you will have your own motherline. For say, Beth Mattimore, it will be her mother Verna and Verna’s mother and so on. For Fr. Jack, it will be his mother Joan and Joan’s mother, and so on.

Because mtDNA tests are less common and only look at one ancestral line instead of all lines, I only have 2,162 DNA matches instead of the 38,000+ I have on Ancestry with my autosomal test. Each of the mtDNA matches are given a genetic distance (GD) to me that measures the number of mutations (differences) between us, and indicates how closely we share a maternal ancestor. A GD of 0 means an exact match, while higher numbers (1, 2, 3+) indicate more distant relationships. I have only four exact matches. But that means they have identical mitochondrial DNA, suggesting a shared common female ancestor in a relatively recent timeframe. Relative is the operative word here. I did not recognize any of the four matches. Their reported maternal countries of origin are Canada, England and UK. They look like pretty distant matches to me, but more research is needed.

Migration Map

Here we see the estimated migration route from Mitochondrial Eve to my haplogroup and the closest connections found in ancient DNA from archaeological remains.

My haplogroup, U5b1d1c4, is a specific, rare subclade of mitochondrial DNA haplogroup U5, which traces a direct unbroken maternal line back to early European hunter-gatherers. It represents a lineage with a highly specific, relatively recent ancestor estimated to have lived around 900 BCE. It is associated with Northern and Western European ancestry, with identified descendant lineages most commonly found in England, Ireland, and the United States.

Ancient and Notable Connections

Some of my connections are considered rare while others are common connections that all modern humans share, like to Neanderthal Man and Denisova 8. Here are a few of my notable connections (click an image to see it larger):

From Cheddar Man to Paris Hilton, oh my!

There is much I don’t yet understand about my mtDNA results and how they may benefit my genealogy research. But I thought it would be fun to share what I’ve learned so far. If you are interested in taking a mitochondrial DNA (or Y-DNA) test, the industry leader for this is FamilyTree DNA based in Houston, TX.

If you’ve read this far, thanks for indulging me in another DNA topic.