Evolution

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There's a name for long-chain silicate molecules. They're called asbestos. I have no idea what aspect of silicon chemistry could be used to produce molecules with the subtle variation that carbon achieves. Certainly there's nothing recognised as alive on this planet which isn't totally dependent on DNA/RNA for storing and expressing its replication instructions.

[Scrat]

I agree there is nothing living to my knowledge that is not carbon based. There may be others we don't see or know about.

Silicon based life or life based on different chemical mediums is possible, methane perhaps. Who knows what we will find in the methane oceans of say Titan or the clouds of Jupiter. I believe that one thing is certain though, they will use some type of physical template to reproduce. The rules of the universe are a constant.

there's no earlier stage which fulfils my requirement of being a stable step which can exist indefinitely waiting for the next step to occur. That's the jump from non-life to life. It's the jump which leaves me puzzled. It seems a huge one to assume to be possible in the single universe we see around us.

There is an earlier stage. It's called chaos, order evolves from chaos given time. The vehicle used is either random chance or outside manipulation. I don't think the first molecule of DNA waited for anything, it was simply lucky enough to reproduce itself fast enough to spread and evolve.