There’s Biblical Eve; Then There’s Mitochondrial Eve

A fascinating genetic fact about women

four sisters
My mother and her sisters. As a group, they had 10 girls, who in turn had 20 girls. Guess my grandmother’s mtDNA is alive and well.

All humans alive today are descended from one, I repeat, ONE woman who lived in Africa between 140,000 and 200,000 years ago. She’s known as our mitochondrial Eve.

This, I submit, is the coolest and most mind-blowing genetic fact about women.

How do we know this?  What the heck are mitochondria?

Following is the best short explanation I, a preschool special ed teacher, am capable of giving.

When we talk about DNA, we refer to the genetic material contained in the chromosomes -you know, those thread-like structures that come in pairs (23 in our case) and that live in the nucleus of all cells (except the egg and sperm cells).

That’s not where DNA ends though. It turns out there’s a tiny bit more in a different cell structure called the mitochondria, little organelles that float in the cell’s cytoplasm and whose main job is to make energy from food.

Ladies and gentlemen, I give you… Mitochondrial DNA, aka mtDNA (and a little illustration I had fun creating on Canva)!

Cell illustration

For whatever reason, only mothers pass on mtDNA to their offspring. Unlike your chromosomal DNA, whose origin is split 50–50 between your mother and father, your mtDNA’s source is 100% your mother’s.

My first thought when I read about mtDNA is that mine ends with me. I have two sons and they’ll never pass down my mtDNA to anyone. It doesn’t matter if they have one, three or seventeen children — or no children at all. Wait a minute, I soon realized, three of my five sisters have daughters, and they will pass down the mtDNA I inherited from my own mother. There you go, then, my mtDNA will live on after I’m gone.

There are, however, more fascinating things to learn from mtDNA beyond mine’s fate.

Mitochondrial DNA has unique characteristics and mutates with a specific frequency. It so happens that a number of unfathomably brilliant geneticists, biologists and programmers have used this information to figure out the ancestry of the whole of existing humanity.

Mitochondrial Eve was not the first woman; nor was she the only woman back then. But for whatever reason, her mtDNA was passed on and on and on and on and on. Maybe she was the one who had the most baby girls who in turn happened to have the most girls who happened to survive and have more baby girls. Or her descendants moved farther and wider across the globe over the generations. No one knows for sure.

For a while there, I was obsessed with the book The Gene: An Intimate History, by Siddharta Mukherjee. It reminded me that the more you learn about any topic, the more you realize how little you know. It’s humbling and marvelous when this happens.

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