[roncesvalles]

I think single origin event is highly likely because, for example, it's wholly conceivable that a slightly different variant of AUCG (or just one of the molecules) could've emerged and it would have similar characteristics, but not differentiated enough that one would have a very strong selective advantage over the other.

Diversity could exist in harmony and the lack of any diversity is a pretty strong signal that the only extant version is either very rare or the only to ever emerge.

Everything in nature is diverse except RNA/DNA and this fact alone is a sort of evidence.

[vlovich123]

Or the basic life that forms is going to look the same regardless of where it starts on Earth, meaning that you’d never have evidence of two origins.

Or RNA was just a winning virus that infected all other life or killed all competition to make it seem like there was only one origin.

Absence of evidence is not evidence of absence.

[roncesvalles]

I'm pretty sure we've checked every lifeform to see if they follow the universal genetic code, and they do. RNA is too fundamental to be a virus infection.

When you should see evidence but don't, "absence of evidence is not evidence of absence" doesn't apply. Otherwise absence becomes unprovable à la Russell's teapot.

[vlovich123]

Except for that you’d have to have a reasonable belief you know what to look for and where to look.

By comparison, we’ve looked nowhere (Earth is big and mostly inaccessible to humans) and don’t know what we should be looking for, since we don’t have any testable models for the origin of life yet.

And re RNA I was just giving one example of why all life might have it (ie RNA gave an evolutionary advantage so anything without RNA died). There’s all sorts of reasons why we don’t have evidence of multiple origins, not least of which is that we just haven’t looked in the right place and there could easily be life being created from scratch on this planet without even knowing about it. That’s what the entire field of synthetic biology is even about; just doing it in a lab instead of out in nature so that we can understand the conditions better.