This post wraps things up with my mum’s mtDNA. I will be sharing some take-away points that I hope will inspire others to work with their own mtDNA inheritance.
However, before I jump straight in to the summary finding, I need to quickly explain two fundamental terms: 1) Haplogroups, and 2) Subclades.
While I tend to avoid using Wikipedia as a professional source of information, it does provide a great overview of what haplogroups are:
Haplogroups are used to represent the major branch points on the mitochondrial phylogenetic tree [a veryspecific kind of scientific, genetic family tree].
Understanding the evolutionary path of the female lineage has helped population geneticists trace the matrilineal inheritance of modern humans back to human origins in Africa and the subsequent spread around the globe.
The letter names of the haplogroups (not just mitochondrial DNA haplogroups) run from A to Z. As haplogroups were named in the order of their discovery, they (meaning the accidental dictionary ordering of the letters) do not reflect the actual genetic relationships.
The hypothetical woman at the root of all these groups (meaning just the mitochondrial DNA haplogroups) is the matrilineal most recent common ancestor (MRCA) for all currently living humans. She is commonly called Mitochondrial Eve.
The rate at which mitochondrial DNA mutates is known as the mitochondrial molecular clock. It’s an area of ongoing research with one study reporting one mutation per 8000 years [Loogvali, Eva-Liis; Kivisild, Toomas; Margus, Tõnu; Villems, Richard (2009), O’Rourke, Dennis, ed., “Explaining the Imperfection of the Molecular Clock of Hominid Mitochondria”, PLoS ONE, 4 (12): e8260, doi:10.1371/journal.pone.0008260, pmc 2794369 Freely accessible, PMID 20041137]. This makes mitochondrial DNA less precise for genealogical dating than Y-chromosome DNA which accumulates one mutation for every 10 years [“Human mutation rate revealed”. Nature News. 2009.].
This mtDNA tree looks something like this partial example:
In genetics, subclade is a term used to describe a subgroup of a subgenus or haplogroup. It is commonly used today in describing genealogical DNA tests of human mitochondrial DNA haplogroups and human Y-chromosome DNA haplogroups.
Let’s use cats as an example. While all cats belong to the Feline mammal family (think of Feline as a haplogroup)…Siamese, Burmese, Person, and the common house cat would each be a different subclade.
Now, let’s get started!
I tested all three regions of the mtDNA I inherited from my mother. It was a full mtDNA sequencing. Based on my sequencing results, I am a confirmed descendent of mtDNA Haplogroup L2, Subclade L2a1c4a on my direct maternal lineage (mother’s, mother’s, mother’s…. maternal line).
My confirmed mtDNA subclade is L2a1c4a. Population studies have not yet been published for the mtDNA Subclade L2a1c4a. Yep, that’s correct. My subclade was created within the past few years. So…there are no peer-reviewed published studies covering it.
However, population studies are available for the direct ancestors of the mtDNA Subclade L2a1c4a. Population studies to date have found that the ancestors of L2a1c4a are found in the highest concentration in Chad Arabs in Lake Chad, Africa.
The major distribution of L2a1c4a
Chad Arabs in Lake Chad, Africa 11.55% > Buduma in Lake Chad, Africa 10.35% > Shuwa Arab in Lake Chad, Africa 7.69% > Central Morocco 5.4% > Mafa in Lake Chad, Africa 5.26% > Gurages in Ethiopia 4.76% > Amharas in Ethiopia 4.16% > Kanembu in Lake Chad, Africa 4.08%.
Studies were conducted by sampling the DNA of indigenous populations and determining the percentage of each indigenous population which belong to the mtDNA Subclade L2a1c4a:
* This table is based on a summary of current research published in peer reviewed journals and will be updated dynamically as more scientific data becomes available for mtDNA subclade L2a1c4a and its ancestors.
The image above is the core, the beating heart, of my mothers mtDNA.
To my fellow Old Ninety-Six County, South Carolina cousins, this is the female line this DNA covers:
My mum < Pauline Matthews < Gertrude Harling < Aurelia Holloway < Amanda Peterson < Violet Williams < Moses Williams, Sr’s unknown first wife (not Mariah Stallsworth).
mtDNA Haplogroup L2 is found predominantly in Africa. The migration map of mtDNA Haplogroup L2 is as follows:
The woman who founded mtDNA Haplogroup L2 is believed to have been born approximately 70,000 to 100,000 years ago in Central Africa. mtDNA Haplogroup L2 is one of the most ancient branches of the mtDNA phylogenetic tree. Today, descendants of mtDNA Haplogroup L2 can be found widely distributed in the African Continent, with a high frequency in Mbuti Pygmies.
The mtDNA tree expands at a rapid rate as new subclades are discovered. As the tree grows, my haplogroup/subclade will be automatically reclassified based the latest version of the tree. This tree was last updated on 18 January 2015 on Genebase, the company I tested with.
So what do we know?
On the face of it, the team knows my mtDNA began in East Africa, and then traveled through the interior of Africa tens of thousands of years ago. It appears my line of maternal female ancestors lived in the Lake Chad area. We don’t know how long they lived in this region. However, for now, the team believes they resided in this part of Africa for millennia. While there, an admixture traveled down from northern Africa to mix within this population before an unknown line of females from the same lineage brought it to the western coast of Africa.
We know that a series of truly ancient maternal great aunts and maternal female cousins took the same mtDNA out of Africa into the Middle East, Europe, Central Asia, Russia, and the Jewish populations of Europe and the Middle East.
The Brazilian results (you will see this in the other posts that are part of this series) indicate that another maternal female cousin, sister, or great aunt from this mtDNA family was taken from Africa and sent to that country.
At the heart of it, I have a dozen or so African cultures that form my direction mitochondrial legacy. Knowing which specific cultures are part of this story has enabled me to extensively read about them. And you know I want to visit them!
Each culture is a part of my history. They are me. And I’d like to know a heck of a lot more about them.
There is one specific application that I would like to use my test results for: identifying the unknown woman who was the wife of my 4x great grandfather, Moses Williams, Sr (1756-1884). I am descent of their daughter, Jane Williams. Moses and this unknown maternal ancestor had 20 daughters in the Old Ninety-Six region of South Carolina. That’s a whole lot of daughters to pass on this mtDNA… especially when the known children of Moses were having between 8 to 12 kids each!
Among the 2,500+ mtDNA matches I have on Genebase…someone may have the missing key to unlocking the identity of this 4x great grandmother…and the identity of her mother…and the identity of her mother.
So, as you can see, we are working with this DNA in more than one way to answer different sets of questions.
A quick reminder about mtDNA
Just so we all know what we’re looking at, here are some illustrations of mtDNA:
Mitochondrial DNA (mtDNA) is the small circular chromosome found inside mitochondria. These organelles found in cells have often been called the powerhouse of the cell. The mitochondria, and thus mitochondrial DNA, are passed only from mother to offspring through the egg cell
As you can see, mtDNA looks very different from the 23 chromosomes that form autosomal DNA (the DNA you inherit from both parents).
For a more in-depth understanding of mtDNA, I invite you to read Roberta Estes’s excellent article Mitochondrial DNA – Your Mom’s Story over at DNAeXplained via https://www.google.com/amp/s/dna-explained.com/2017/05/09/mitochondrial-dna-your-moms-story/amp/