[This idea was born as a comment here, but I decided to create a separate post out of it].

What if your mother stood right behind you, and your mother’s mother stood right behind her? Then your great grandma and then your great great grandma. Imagine them all lined up, one foot apart, stretching out into the distance. If a generation is deemed to be 25 years, a line of your ancestors as long as a football field (300 feet) would stretch backwards 7,500 years.  The woman at the end of that 300 foot line would have lived during the time when agriculture just began in ancient Egypt. You’d still recognize each of your ancestors in that 300 foot line to be fully modern humans, biologically speaking.

Isn’t it amazing to think that you could run along side that entire 300 foot line of your ancestors in only 15 seconds (I’m assuming you’re not an Olympic caliber sprinter) to end up standing next to one of your own ancestors who was alive 7,500 years ago?

Now think even further back.  In An Ancestor’s Tale, Richard Dawkins calculated that 20,000,000 great-grandparents ago, our relatives were small shrew-like animals living at the end of the Cretaceous period. What if you spaced out your relatives one foot apart to extend all the way back to these shrew-like creatures? That line would be 3,787 miles long. That’s about the length of highway running from my hometown of St. Louis, Missouri to Anchorage Alaska. Imagine speeding alongside that line of your relatives at 60 mph, seeing the generations of your relatives whizzing by, more than 5,000 of them every minute.

It wouldn’t take long to reach the last of your relatives who looks like you. In fact, your trip would have barely begun.  Biologically modern humans (those whose bodies are the functional equivalent of our own bodies) came onto the scene between 100,000 and 200,000 years ago.  Driving at highway speed parallel to that line of your own relatives, you’d run out of your biologically modern human relatives less than one-minute after beginning your trip. That’s only 4,000 generations.

If you wanted to drive all the way out to see your shrew-like relatives (at 60 mph), you’d need to drive alongside that entire 3,787 mile long line of relatives.  It sounds daunting, but you could do it in only 63 hours.  That’s only 63 hours of driving to get back to your relatives who were literally shrews!

You can’t possibly write a work of fiction that is more amazing than these facts.

We are all survivors. If any one of those ancestors failed to survive long enough to reproduce, you wouldn’t be there to read this post.  For me, that is an extraordinary thought. Just think of how likely it was that you would never exist, which brings me back to the idea of the post from which this post sprang.

[After originally publishing this idea, “Ben” wrote this comment]

First and foremost, it would probably only take me 13 seconds to run the football field. That is, if I was not so intrigued by the figures I pass, to stop and have a quick chat. I’m a bit (lot) confused though. My mind can’t seem to get past the first few generations, without straining, then I end up at the end with a rodent. Are the folks (mice) way back at the beginning still my *direct* descendants? Or is there some extinctions or branching out or… okay it is just too hard to comprehend, for me.

Another interesting thing, not that it really matters, but EVERYONE reading this is part “black”.

DNA studies have shown that people shared a common ancestor who lived in Africa between 50,000 to 200,000 years ago. As our ancestors migrated out of Africa into the rest of the world, small changes called mutations occurred in their DNA. As generations passed, each mutation links our ancestor to a specific time and place in history. The mutations that we find in our own DNA tell the story of our own ancestral past.

[My response to Ben]

Ben, after you run past the football field length line, just to get an idea, you may, indeed, come back and chat with some of these folks.

I would love to see the looks on the faces of so many bigots as they started noticing that the skin color and facial features of their own relatives started to change as they drove past that long line of their relatives. After only one-half mile, only 30 seconds of driving, they would start noticing that they were driving past their ancestors who lived in Africa “only” 60,000 years ago. They would start noticing their australopithecine ancestors after driving for only 30 minutes.  If those bigots started their hypothetical driving trips from St. Louis, they’d notice their australopithecine Grandmas even before they left the St. Louis area. This makes me wonder . . .  would they get out of their car and hug their hairy naked ancestors or would they vomit?

Someday I’m going to write a post called “I am African.”  The idea is that it doesn’t matter who you are–you come out of Africa.  Consequently, on the Census form and other forms that ask the meaningless and divisive “race” question, my habit is to check all relevant boxes, including “African,” because that’s where at least some of my ancestors are from. This is a thought that liberates, because it reminds me that we’re not so different from different-looking others after all.

Since my highway drive is a thought experiment–let’s take the thought to an extreme.   Let’s assume that all of your female relatives standing in that line were sexually mature adults. I’d bet you’d think some of those women were fetching.  The incest taboo wouldn’t kick in (no Westermarck effect), because you weren’t raised in the same house with most of them. This might cause you a conundrum. If you can marry a second cousin, can you marry your great great great (X20) grandmother? The shared genetic material you share with that woman would be far less than that of your second cousin. Such a potential, hypothetical conundrum! Not that I’m driving all the way to Alaska and dating a shrew!