She isn't the first woman. She's a moving target.

You’ve probably heard of Mitochondrial Eve, and if the name conjures a lone first woman standing at the dawn of the species, that’s the wrong picture — and the right one is far stranger.

Mitochondrial Eve is simply the most recent woman from whom every living human descends through an unbroken female line — mother’s mother’s mother, all the way back. That’s the whole definition. She is not the first woman, not the only woman of her time, and not any kind of bottleneck. When she was alive — current estimates put that roughly 150,000 to 200,000 years ago in Africa, though the figure keeps getting revised as methods sharpen — she was one of many thousands of women. She wasn’t special while she lived. She became “Eve” only in hindsight, through a quirk of bookkeeping.

The bookkeeping is mitochondrial DNA. Your mitochondria — the little power plants inside your cells — carry their own small loop of DNA, and you inherit it almost entirely from your mother, who got it from hers. It doesn’t shuffle together with your father’s the way the rest of your genome does. That makes it a clean maternal thread you can follow straight backward. Follow everyone’s thread back far enough and the threads begin to merge. Eventually — and this is a mathematical near-certainty for any such non-shuffling lineage, not a lucky coincidence — they all merge into one. That merge point is Eve. The name for the inevitability is coalescence.

Here’s the part that trips people up. The thousands of other women alive alongside Eve have plenty of living descendants today — probably including you. What they lack is an unbroken female line to the present. Somewhere down the generations, one of those lineages reached a woman who had only sons, or no surviving children, and the maternal thread was cut — even as the family itself flourished through those sons. A son passes his mother’s mitochondria to no one. So a line can end without the family ending. Extinction of a matriline is quiet and ordinary; it doesn’t require anyone to die young.

And now the strangest part. Mitochondrial Eve is not a fixed historical figure the way the first king of some place is. She’s defined entirely by who is alive now. As maternal lines keep winking out — as they always do — the title can creep forward in time to a more recent woman. If enough of today’s matrilines eventually end, some woman who lived after our current Eve becomes the new most-recent-common-maternal-ancestor. Eve is less a person than a position, and the position is held by whoever happens to sit at the bottom of the last surviving merge. Run the species forward a few thousand years and “Eve” may turn out to be someone alive right now.

There’s a male counterpart — Y-chromosomal Adam, traced the same way down the father-to-son line. The tabloid version imagines the two as a couple in a garden. They weren’t. They almost certainly never met, likely lived many thousands of years apart, and were each surrounded by multitudes. They’re two independent accounting artifacts of two different non-shuffling threads.

What I like about Mitochondrial Eve is how much it corrects at once. It isn’t a story about a first mother. It’s a story about how a whole population looks when you trace a single thread through it — how everything converges if you follow one rule backward, how a lineage can end without a death, and how the ancestor you’d want to call “first” is really just a shadow cast by who’s alive to count. The deepest point in your family tree keeps moving. It depends on us.