The hardest part of the transition from prebiotic chemistry (assembling the building blocks) to an 'RNA World' is doing so in a way that can support RNA copying. As others have shown the chance of finding one replicator is low - so you need supporting RNA copying chemistry at a pretty substantial level to help that happen.
This is where the hard part of the field is currently: finding chemistry that can support accurate RNA copying that is also both sufficiently high yielding and also compatible with these reactions being inside protocells (fatty acids for example). An RNA genome only really has value when it can be selfish and keep any innovations it makes to itself inside a protocell!
I work in Origins Research - if you have questions please ask and ill try to answer with the current opinions of the field!
It seems obvious that if replication of elementary particles appears that everything else will be an emerging property given enough time. And if you look at atoms and math there're definite parallels that once atoms can interconnect stronger than everything else (considering the 3d world) and something like Penrose's tiles where you get repeating interconnecting structures that more higher level structures would be possible. And with energy connected to the particles momentum and Heisenberg's uncertainty principle you get fluctuations in the structures that allow for both new structures and enforcing of the construction rules. You also have clear levels between forces that work on different levels that create boundaries to the structures. 3 spacial dimensions give additional directions of interactions between structures. And voila, given conditions, there's a place for emerging properties. Whether it was RNA who knows. It does seem that the search becomes way murkier toward going into the actual mechanism but the ingredients seem to be in place
Most mutations are negative dead-ends, not unlikely DNA now where most pregnancies spontaneously abort due to errors. But life has many, many chances — especially at the molecular scale. So what’s the actual problem?
Similarly, if you have a soup of 10-15 nucleotide sequences, what are the odds actually that they’d link into larger segments?
Let’s suppose that density is a million times lower than blood, so you have one picogram per gram of water. There are 10^24 grams of water on Earth’s surface and 10 base pairs weighs 10^-20 grams, giving us approximately 10^32 segments of that length.
Feel free to play with my numbers, but I’m supposed to believe that with ~10^30 pieces, we can’t have ten of them form the right sequence?
Your numbers are fine - but RNA is fragile; making one copy of something really rare will not be able to do anything as it will not last long enough to meaningfully contribute.
Interestingly we now are thinking about ways to use mutations in other ways, youve spent a lot of energy making these polymers, so it would be a shame to waste that right? We think that they can be used to assemble larger functional pieces as mutations are mostly deterministic meaning you'll get the same kinds of errors - so why not put them to use!
A combinatorial explosion. To have mutations you need to have replication first. If a smallest viable self-replicator is, say, 100 nucleotides long, and there's not many other such replicators of the same length, the improbability of its spontaneous formation (~4^-100) dwarfs any amount of material available on Earth.
The researchers have found QT45 replicator. But it replicates other RNA strands, that is it needs another replicator nearby to replicate itself, which brings the probability down to 4^-90 range.
And it's not clear from the article whether QT45 is a viable replicator. That is whether it is stable enough and replicates other RNA strands correctly enough to sustain exponential growth instead of petering out due to filling its surroundings with broken copies that don't perform replication before decaying itself.
I doubt a replicator came out of thin air. It seems more likely, at least to me, that we started with constructors, that created primitive sequences.
Imagine you have molecules that can form spontaneously, like gliders in Conway's Game of Life. You may have several different molecules that are capable of helping to create one another -- an autocatalytic set.
Eventually this could result in more complex chains, and eventually a self replicating molecule can arise.
Imagine slamming a bunch of gliders together to make a machine that replicates more gliders. It's possible! Not likely, but there are so many variables that can influence the environment substantially. It's not like there was a giant homogeneous soup. Parts from over here and over there would form differently and when they meet, amazing things can happen.
In the Game of Life, this spontaneous event is extremely unlikely, astronomically unlikely.
Unlike Game of Life, the real world has a few advantages that improve performance. For one, it's less fragile. Bonds are much stronger and collisions don't cause everything to break. Another advantage is that bonds are attractive: molecules can rotate and turn to snap together strongly. Gliders just explode violently. And finally, the real world is very dense. We're talking trillions of molecules mixing around millions of times per second per microdroplet. Compound that with a few hundred million years... it certainly doesn't feel as surprising as you might expect.
If there were a highly advanced alien race watching earth over a long period of time, it might be interesting, but not unexpected, that suddenly an Eiffel tower springs forth from the surface of the planet, erected by intelligent organisms.
The simple combinatorial explosion criticism feels reductive to me. It's exceedingly unlikely that a single "self-replicating RNA molecule" formed independently by chance and then propagated.
Let's say that you have some RNA soup with some ribozymes some of which weakly encourage some reaction involving other RNA molecules. The occurrence of a cycle of reinforcing reactions might be sufficient to build a crude evolutionary ratchet.
In fact the "cycle of reactions" perspective feels a bit more robust to me since it allows for the proto-replication process to take place over a longer period of time and over larger areas.
Yeah, it's more probable, but it still can be false. For example, such reaction chains might not lead to a sufficiently probable increase in complexity.
Life didn't have to start on Earth. It could have started on any one of an unbounded number of worlds. It's only in retrospect that this world seems special.
What's the probability of spontaneous formation across an infinite universe?
In an infinite universe even events with probability 0 can happen[1], but it's hard to find this explanation satisfactory. Any hypothesis that raises probability of abiogenesis to make it likely to happen at least in the observable universe looks more satisfactory than "but it could have happened anyway in an infinite universe despite being totally improbable."
If you mean panspermia specifically in respect to earth it's a lot more bounded in space and time to the parts that were close enough to interact with earth, but if not then yes there is probably anything that can be represented by atoms out there somewhere or other.
I also don't understand. Adding billions of years to your numbers probably makes it an even better point.
"Life's first molecule." Take your favorite quantum field theory and consider how it draws a line between a molecule and not a molecule. Consider how it draws a line between life or not. That'd be cool. Consider that it doesn't give a shit who did what first.
This is where the hard part of the field is currently: finding chemistry that can support accurate RNA copying that is also both sufficiently high yielding and also compatible with these reactions being inside protocells (fatty acids for example). An RNA genome only really has value when it can be selfish and keep any innovations it makes to itself inside a protocell!
I work in Origins Research - if you have questions please ask and ill try to answer with the current opinions of the field!
Most mutations are negative dead-ends, not unlikely DNA now where most pregnancies spontaneously abort due to errors. But life has many, many chances — especially at the molecular scale. So what’s the actual problem?
Similarly, if you have a soup of 10-15 nucleotide sequences, what are the odds actually that they’d link into larger segments?
Let’s suppose that density is a million times lower than blood, so you have one picogram per gram of water. There are 10^24 grams of water on Earth’s surface and 10 base pairs weighs 10^-20 grams, giving us approximately 10^32 segments of that length.
Feel free to play with my numbers, but I’m supposed to believe that with ~10^30 pieces, we can’t have ten of them form the right sequence?
Interestingly we now are thinking about ways to use mutations in other ways, youve spent a lot of energy making these polymers, so it would be a shame to waste that right? We think that they can be used to assemble larger functional pieces as mutations are mostly deterministic meaning you'll get the same kinds of errors - so why not put them to use!
A combinatorial explosion. To have mutations you need to have replication first. If a smallest viable self-replicator is, say, 100 nucleotides long, and there's not many other such replicators of the same length, the improbability of its spontaneous formation (~4^-100) dwarfs any amount of material available on Earth.
The researchers have found QT45 replicator. But it replicates other RNA strands, that is it needs another replicator nearby to replicate itself, which brings the probability down to 4^-90 range.
And it's not clear from the article whether QT45 is a viable replicator. That is whether it is stable enough and replicates other RNA strands correctly enough to sustain exponential growth instead of petering out due to filling its surroundings with broken copies that don't perform replication before decaying itself.
Imagine you have molecules that can form spontaneously, like gliders in Conway's Game of Life. You may have several different molecules that are capable of helping to create one another -- an autocatalytic set.
Eventually this could result in more complex chains, and eventually a self replicating molecule can arise.
Imagine slamming a bunch of gliders together to make a machine that replicates more gliders. It's possible! Not likely, but there are so many variables that can influence the environment substantially. It's not like there was a giant homogeneous soup. Parts from over here and over there would form differently and when they meet, amazing things can happen.
In the Game of Life, this spontaneous event is extremely unlikely, astronomically unlikely.
Unlike Game of Life, the real world has a few advantages that improve performance. For one, it's less fragile. Bonds are much stronger and collisions don't cause everything to break. Another advantage is that bonds are attractive: molecules can rotate and turn to snap together strongly. Gliders just explode violently. And finally, the real world is very dense. We're talking trillions of molecules mixing around millions of times per second per microdroplet. Compound that with a few hundred million years... it certainly doesn't feel as surprising as you might expect.
If there were a highly advanced alien race watching earth over a long period of time, it might be interesting, but not unexpected, that suddenly an Eiffel tower springs forth from the surface of the planet, erected by intelligent organisms.
Let's say that you have some RNA soup with some ribozymes some of which weakly encourage some reaction involving other RNA molecules. The occurrence of a cycle of reinforcing reactions might be sufficient to build a crude evolutionary ratchet.
In fact the "cycle of reactions" perspective feels a bit more robust to me since it allows for the proto-replication process to take place over a longer period of time and over larger areas.
What's the probability of spontaneous formation across an infinite universe?
[1]https://en.wikipedia.org/wiki/Almost_surely
"Life's first molecule." Take your favorite quantum field theory and consider how it draws a line between a molecule and not a molecule. Consider how it draws a line between life or not. That'd be cool. Consider that it doesn't give a shit who did what first.
"given any word, there's no such thing"