[ceejayoz]

I'm aware of the Miller-Urey experiment.

It's only one piece of the puzzle, and we're aided significantly in it by knowing what the results are supposed to look like.

[throwup238]

We absolutely know what it’s supposed to look like: monomers. Monomers that can form polymers.

The specific chemical details are irrelevant. We have no evidence of other monomers that could enable non-water based life.

[ceejayoz]

We find polymers outside of Earth-like conditions.

https://en.wikipedia.org/wiki/Hemoglycin

[throwup238]

> Hemoglycin (previously termed hemolithin) is a space polymer that is the first polymer of _amino acids_ found in meteorites.

I’m done, have a great day! (Monomers)

Edit: My apologies for being dismissive. I’d like to get into the specifics of why amino acids (amino and carboxylic groups specifically) are special, and interesting exceptions like hydroxy and alpha-hydroxy acids, but I’ve got to get to work and I could spend an entire year explaining the nuances. The deeper you get into the details, the more the anthropic principle rears its ugly head.