Check out Part 2 of the series here.
What about the middle stages? The march from single-celled organisms doing their single-celled thing to intelligent creatures that can wield tools and leave feedback reviews about them?
Well, again we still only have one data point, but we MIGHT be able to learn something about filters both small and great in those middle stages. And that’s the fact that intelligent life appeared very LATE on earth. Check this out, within 500 million years of our planet even forming, self-reproducing molecules and single-celled critters evolved. And here we are, intelligent creatures, only arising into consciousness within the past few hundred THOUSAND years. And guess what? We’re about to get cooked. No, that’s not a metaphor. As the sun ages it expands and brightens. It’s been doing so for…well, four and a half billion years already. That’s right, the first life to appear on the Earth knew a small, dimmer Sun than we do today. And it’s only going to get worse. Within about five hundred million years from now, the Sun will become so hot that the oceans will boil, plate tectonics will grind to a halt, and the greenhouse effect will spiral out of control, turning the Earth into another Venus: superheated and choking on its own acidic atmosphere. While life might – might - cling to a miserable existence in some crevice in that future hell-world, it’s definitely not going to be intelligent, let alone space-faring.
In other words, we are here, building our rockets, in the final stages where it’s even possible to do on the Earth. Now again, I have to sprinkle a lot of caution into these statements, but again maybe nature is trying to tell us something. Life itself appeared within the first chapter of the Earth’s viable history, and intelligent life appeared in the last.
So maybe that’s the answer: life is common, but intelligent life is not. Maybe that’s the Great Filter. Intelligence takes a lot of luck and stable evolutionary history (and maybe a few good whacks with an asteroid). So we shouldn’t expect other space faring civilizations because intelligence is a precious commodity in the cosmos (and on the Earth, yuk yuk).
How could we test this? Or, maybe “test” is too strong a world, but at least start to wrap the questions in some sort of statistics or probabilities. After all, so far we’re only going on one example. But we can imagine a future where we are able to find microscopic critters, maybe deep in the Martian crust, or swimming in the seas of Europa, or hanging out on some exoplanet. If we continue our searches and find simple life, but no signs of INTELLIGENT life, then this would be a major clue that the Great Filter is behind us: that we’re already on the other side and it’s all going to great.
Or not. “Not” is definitely still an option.
Until we have enough data to build statistics, and trust me that’s going to be a long way off so don’t hold your breath, then all we have is speculation. Which while not very scientifically rigorous is still really fun. What if the Great Filter is in front of us? What if it’s in our future? What if once life gains a foothold somewhere it has a universally decent chance of arising to intelligence, like it’s a foregone conclusion of the evolutionary process?
Well then, that means that maybe species simply destroy themselves. I mean, it’s not hard once you put your mind to it. The idea is that to travel interstellar, or even interplanetary, distances, you must be able to harvest, store, and use incredible amounts of energy, and develop a sophisticated technological base to do it. And if you can do that, then you can harvest, store, and use MORE THAN ENOUGH ENERGY to wipe every single living thing off the face of your home planet.
The best insurance against that is to have your favorite kind of living thing on multiple surfaces on multiple planets, but you will have to spend a certain amount of time – maybe centuries, maybe millennia – in a precarious balance, where you’re trying to climb the ladder to the stars without cutting yourself off at the knees. A species needs to use its technologies for good, not evil, for a very long time so that it can ensure its own survival. Meanwhile, during all that time slowly developing space travel and self-sustaining offworld habitats, a rogue state or actor or even the combined actions of the entire species can just...end it all.
And, like, THAT’S US. We can send robotic craft beyond the edges of the solar system. We can send crews to live months at a time in orbit. And…we can also wipe every living thing off the face of the earth. We have more than enough nuclear weapons to kill off all of humanity and trigger a mass extinction. If we pump enough carbon into the atmosphere, things can go haywire real quick and have the same effect. The same abilities that bring us to the stars can bury us in the dirt, which is real dark but kinda poetic.
Or maybe it takes so long that nature does the job for us, sending an unlucky rock in our direction or an ozone-killing blast from a gamma ray burst. Life may be hardy in general but individual species are not. Something – from nature or from ourselves – can kill us while we’re still in the cradle.
Remember, for the great filter argument to work, it has to be NEAR TOTAL. Which means…this is it. The end of the line. The last stop before galactic extinction. Goodbye everyone, hug your loved ones, and take one last bite of cheese, because the end of our species is right around the corner.
Wow, that got morbid.
