Eli5 : could there be a life without DNA or RNA on earth ? On other planets ? If yes, how humankind would discover it ?



Eli5 : could there be a life without DNA or RNA on earth ? On other planets ? If yes, how humankind would discover it ?

In: Biology

So at one pont they thought prions where the only things without DNA and RNA but that was disproven a while ago. There is a possiblity if not a certainty that life could exist elsewhere without dna or rna. But what ever
It uses may be close to DNA or RNA but using a different protein. There is also theory that silaca or non carbon biased life could exist which would use nothing even remotely similar to DNA or RNA

On Earth, it’s theoretically possible. In the total of the universe, it’s practically guaranteed (unless RNA is literally inevitable, which by our current knowledge it doesn’t appear to be). Part of it is dependent upon how you define life. Anything capable of self-replication – that is, making molecules around it into copies of itself either deliberately or as a side effect of something it does – could count as life on the very basic level. How many more prerequisites you want to add before you consider something “life” will change the likelihood of it existing without RNA. In laboratory settings, something called XNA has been made, which is an artificial cousin of DNA and RNA, and has shown to possess many of the same capabilities RNA has (and thus could theoretically serve as the basis for an entire new kind of life, same way RNA has), and there are probably other molecules out there too that possess the same capabilities.

Discovering such life could be very difficult. On other planets, we can only detect the traces life leaves behind, not life itself – things like organic molecules and oxygen-rich atmospheres. If such life looked the same as RNA-based life in its traces then we’d have no way of confirming it wasn’t RNA-based. If it *didn’t* look the same, then we’d probably not even notice its traces. On Earth, such organisms may well have existed back at the dawn of life. In fact, I’d go so far as to say they probably *did*, given that it seems unlikely that the only molecule to come out of the primordial soup and do anything whatsoever would be RNA. If they did, then they would likely have been outcompeted by RNA-based life, based on the fact everything we know so far has been RNA-based (if they had co-existed evenly or RNA had been inferior, I’d be typing out a very different comment right now). If any non-RNA-based life still exists on Earth, it probably does so in extreme environments that are difficult to access or test. It’s also quite possible that such organisms would be so vastly different to anything we know as life today that we wouldn’t realise it was life even if it jumped up and punched us in the face.