Play a game with me for a moment.
Think about a person. They might be anyone. Even you.
For the purposes of this game, let’s picture this person as an individual, existing on a uniform plane in otherwise empty space. (Imagine they don’t need a breathable atmosphere in this game)
Now, let’s imagine this person walking at a constant speed of 1.3 m per second in a straight line. Over 5 years they’ll cover over 200,000 km. And be quite tired.
Assuming our imaginary person has aged over that time, their physical body will have changed. Let’s imagine that we take regular 3D snapshots of this person as they walk, at very close intervals, like recording a 3D video. If we show all of this recording at the one time, we see a long person shaped tube with undulating exterior, that changes across its length. Perhaps our person was 5 when they started and is now 10, so they’ve grown during that time. The tube grows accordingly.
Let’s think of this ‘tube’ as a spacetime portrait of our person, because it records the space they inhabit across a particular time period. In this case it will be a straight(ish) volume, since they’ve been walking in a straight line at a constant pace for the whole time. Perceived across time, this is our person.
It’s not a huge leap to imagine what this portrait might look like if you and your everyday activities were the subject. While infinitely more complex, it’s essentially a long tangled tube, punctuated with patterns of regular behaviour. At the macro scale, mine would have semi-regular blobs of sleep in the same place, daily cycles back and forth to work, weekly randomness of weekend activities, and annual sojourns to summer holidays, for example.
Let’s take the 5 year tube we’ve just mapped for our imaginary 10yo, and extend it in both directions: our subject gets younger and smaller as we travel back in time, and older as we journey in the opposite direction.
What happens when we travel far enough back to reach the moment of their birth?
Let’s imagine this for a moment: At some point, our (infant) person is reconnected with the umbilical that joins them and the placenta in the womb of their mother. At this stage we introduce another person (their mother) whose spacetime portrait overlaps with our original person for typically 9 months, where it then typically joins a third spacetime portrait of their father.
These moments have many complicated shapes and spacetime geometries, but as far as I know, we still haven’t found a way to reproduce without having something from two separate humans.
What can we make of this? Viewed through the lens of time each of these “individuals” is actually just a branch of the one organism.
Let’s zoom out and track this branching back, through generations. Travelling through history, we can chart a tree of humans. According to evolutionary theory, at some stage a long way back we’ll join up with the branches of what we now call other species.
Keep pushing back and current theory suggests that we reach a common point where reproductive life began on our planet.
How does this thought experiment affect your view of our “selves” ?