Congratulations. You’re alive. There’s an unbroken thread that stretches across more than three billion years that connects us to the first life that ever touched this world. Think of how tough, resourceful and lucky all of our countless ancestors must have been to survive long enough to pass on the message of life to the next and the next… and the next generation, hundreds of millions of times… before it came to us.

There were so many rivers to cross, so many hazards along the way. Predators, starvation, disease, miscalculation, long winters, drought, flood and violence. Not to mention the occasional upheavals that erupted from within our planet and the apocalyptic bolts that come from the blue.

No matter where we hail from or who our parents were, we are descended from the hearty survivors of unimaginable catastrophes. Each of us is a runner in the longest and most dangerous relay race there ever was, and at this moment, we hold the baton in our hands.

The past is another planet. And so is the future. Some 250 million years from now, many geologists think that the lands of the Earth will be united once again.

All this beauty will have vanished and the Earth of our moment in time will take its place among the lost worlds. The great internal engine of plate tectonics is indifferent to life, as are the small changes in the Earth’s orbit and tilt and the occasional collisions with little worlds on rogue orbits. These processes have no notion of what has been going on over billions of years on our planet’s surface. They do not care.

Each of us is a tiny being riding on the outermost skin of one of the smaller planets for a few dozen trips around the local star. The things that live the longest on Earth endure for only about a millionth of the age of our planet. So, of course, the individual organisms see nothing of the overall pattern. Of changing continents… climate… evolution. That we understand even a little of our origins is one of the great triumphs of human insight and courage. Who we are and why we are here can only be glimpsed by piecing together something of the full picture, which must encompass eons of time… millions of species… and a multitude of worlds.

In this perspective, it’s not surprising that we’re a mystery to ourselves and that, despite our manifest pretension, we are far from being masters of our own little house. This new corridor has no name above the entrance to designate its epoch, and we don’t yet know which failed species will be memorialized within its walls. What happens here, in countless ways, both large and small, is being written by us. Right now.