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Did Life Begin in an RNA World?

56 points • by acossta • last Monday at 5:27 PM • 20 comments • view on HN

Comments

alphasm • today at 6:23 AM

Is there a reason why the alternative idea of closed autocatalytic sets from Stuart Kauffman doesn't get nearly as much attention or discussion as the RNA origin hypothesis?

Ever since I first learned about it, it seems to me a much more likely origin of life hypothesis, as it doesn't require something to catalyze itself, which causes inevitable problems with mutation causing loss of catalytic efficiency.

Also, it is not incompatible with RNA being one of the early building blocks. It just doesn't require RNA to be where everything started.

buryat • today at 4:43 AM

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

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Neb_OoL • today at 5:28 AM

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!

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zmgsabst • today at 2:52 AM

I don’t understand the objections:

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?

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lakt42t • today at 3:55 AM

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