[SinJin]

From what I've gathered, there exist theories that say we can trace the origins of life back to amino acids spontaneously forming on Earth, giving rise to more complex structures that eventually led to what we see today. I know there was some insight to this process shown in the Urey-Miller experiment. I was wondering if we know whether that was the only form of organic matter possible in those beginning conditions, or if there were other paths the building blocks could've taken. I don't know much about biology but would enjoy hearing from someone who does.

[Marko]

I think that in these beginning conditions there were other chemical reactions, but what we see today are the 20 amino acids that are responsible for building a protein, and these were the most successful in this distant past. Probably there were other amino acids, but they were like a “blind road”. Since the carbon atom is the most appropriate for building any complex structure (amino acids, proteins) related with life, and the water is very good solvent, it is hard to imagine any other chemical combination that could lead to life.

However, there were some speculations that life could have been based on silicon, and that alternative solvent could be ammonia. However, both silicon and ammonia failed a lot of tests that carbon and water passed, so it seems that carbon and water as a solvent are the best elements for the base of proteins.

These alternatives are pointed toward the planets, those starting conditions differ from the Earth’s beginning conditions.