Who Were Your Millionth-Great-Grandparents?

Human civilization began about 10,000 years ago with dawn of agriculture (give or take a millennia or so). This seems like such a long time that it can be hard to reconcile with the short span of our lives.

But there is another way to look at it that puts not just civilization, but the whole of your ancestry, in a different light.

Each of us constitutes a generation. We are the children of our parents who were the children of their parents (your grandparents) who were children of their parents (your great-grandparents).

You are, therefore, the latest step in a ladder of generations stretching backward in time and history. If we take each generation to be 25 years in length, then we can see something remarkable unspool.

Between the dawn of civilization and now, there have been just 400 generations. Let's call each generation a "grandma" ("great-grandma" would be more accurate of course). What our little calculation shows is there are only 400 grandmas separating you and your first ancestor who put the Earth to plow.

If you close your eyes for a few moments, you can try imagining the line stretching back from you to your parents to your grandparents to your great-grandparents, etc., ticking off "grandmas" until your reach someone working in some field 10,000 years ago in a world of endless forests, fields, oceans and mountains.

It's kind of staggering to see how much has changed in so short a time.

But you can go further. That's when your mind will really get blown. There is no reason to stop at 10,000 years. The line that led to you reaches back beyond civilization to humans wandering in tribes across glaciers in the last ice age 50,000 years ago. It also reaches further back to species that weren't Homo sapiens, like Homo erectus, a million years ago. Keep going long enough and you'll find "grandmas" who were small mammals living in forests.

The generations that led to you go way, way, way back (the video below from PBS does a wonderful job of laying out that line.)

So who were your millionth-great-grandparents? They are back there somewhere in the deep time that makes up Earth's braided history of life and change. All that struggle, all those moments of hunger, fear, satisfaction and calm: It all happened. And for this one brief moment you represent the tip of that spear. You are the current generation, not just of humans, but also of all life on this lovely blue marble.

Seems like we should all try to enjoy it as much as we can.

Adam Frank is a co-founder of the 13.7 blog, an astrophysics professor at the University of Rochester, a book author and a self-described "evangelist of science." You can keep up with more of what Adam is thinking on Facebook and Twitter: @adamfrank4

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