Why would finding life on Mars be bad news?
Robin Hanson argued in 1996 that the empty sky means some step toward a spacefaring civilization must be improbable. By that argument, independent life on Mars would hint that the hard step is still ahead of us.
▶ Start the storyBecause of what a silent sky might mean about us. Robin Hanson argued in his essay "The Great Filter – Are We Almost Past It?", first written in 1996, that failing to find extraterrestrial civilizations implies something is wrong with the arguments that advanced intelligent life is probable. There must be a barrier somewhere between the first chemistry and a civilization that spreads through the universe, and that barrier is the Great Filter. It is one possible resolution of the Fermi paradox.
The key question is whether the barrier is behind us or ahead of us. Hanson's list has nine steps, from the right star system and reproductive molecules like RNA to a colonization explosion. If the list were complete, at least one of them would have to be improbable. If it is not an early step in the past, the improbable step lies in the future, and humanity's prospects of reaching interstellar colonization are still bleak.
Behind us
- An early step is the hard one
- Good news for our future
Ahead of us
- The hard step is still to come
- Bad news for our future
Now Mars. If we found multicellular life there, and it evolved independently of Earth's, that would imply steps 2 to 6 are easy. The big problem would then lie in steps 1, 7, 8, 9 or an unknown step, and several of those are ahead of us. That is why, by this argument, such a discovery would be bad news. Hanson put the general point in his essay: "The easier it was for life to evolve to our stage, the bleaker our future chances probably are." It is a conditional argument, and others contest its premises.
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Recap
The Great Filter hypothesis says at least one step is very hard, so the easier the early steps look, the more likely the hard one is ahead of us.
💡 A trick to remember it · A funnel with a tiny hole: if we are still above the hole, it is ahead of us, and if we find another drop that passed through the early rings, the hole must be lower down.
Surprising fact · By the Great Filter argument, finding independent multicellular life on Mars would be bad news.
Sources (3)
No source, no claim. Every fact in this lesson (21 claims) cites at least one of these.