It’s not really news after a decade, but I still think it’s worth a look. This is something I think about sometimes, and it’s better to let the actual scholars speak.
For whatever reason it’s not mentioned as a candidate great filter very often even though nearly all the later steps on the path to complexity have happened more than once, and there’s lots of habitable looking exoplanets.
Edit: To be clear, this says that just because life started early on Earth, doesn’t really provide much evidence it’s an easy process, if you allow that it could possibly be very unlikely indeed.
Can someone explain for the layperson?
Sorry, it’s hard to stick not patronising but clear sometimes. Relevant XKCD, although I’m just an enthusiast.
Basically, if broken down mathematically, the fact that life started quickly on our planet may not mean anything. It started sometime in the first 0.5 billion of maybe 10 billion habitable years, which is suggestive, but if the chances are potentially 1:10100 every million years (like it might be if a local spontaneous reversal of thermodynamics was required) it’s a drop in the ocean. Beyond that the only reason we think abiogenesis might be likely are unfinished guesses at how it could happen, so one could argue we don’t see aliens because there never were any in the first place. That’s a minority position at this point, so it’s interesting.
Uh, so vocabulary that not everyone knows:
Abiogenesis - The start of life for the first time from non-living matter.
Great filter - The galaxy isn’t visibly full of aliens, but it should be given the age of the universe. One or more thing (the “filter”) stops it from happening at some point on the way to getting there.
Posterior probability - A probability of something reconstructed using Bayes’ rule. In this case, the reconstructed chance abiogenesis is likely given that it started early on Earth and we’re here to observe it. Not really required to understand the conclusion.
I’m probably safe with habitable planets and the basic concept of evolution of more complex creatures from simpler ones, since this is a science sub.
Ah OK, so this paper argues that given the right conditions the appearance of life is not necessarily likely. Basically it’s hard to know for sure with a single example (Earth). If it is in fact unlikely, it could explain why we haven’t met extraterrestrial life already. Thanks!
Yes! Although it’s less “right conditions” and more “spontaneous appearance, given perfect conditions”.
