The double helix of DNA... is composed of two long chains [of 'letters'] that snake around each other... each strand providing an exact template for … - Nick Lane

Life as we know it has both, and the people who say s first are in effect saying, "Well, there's plenty of s, there's plenty of RNA. The environment's providing it for free," without worrying themselves too much about what kind of an environment is going to provide all of that for free, and by definition, an environment which is effectively metabolically sophisticated enough to provide s is non-living and therefore not part of the question, so they're just pushing it aside. I would say that the whole metabolic side is needed to give rise to genetic information and nucleotides in an RNA world in the first place, that it would be a dirty RNA world contaminated with s and s, and s and things...

I would say that if there's a probability of life being cellular, which I think there is. Life being based, which I think there is. Life starting out with CO₂ because it's so common in planetary atmospheres, and , which is very common, from the kind of s which I'm talking about... and liquid water. They need liquid water for , but we know of it on ... on Europa... [Serpentinization] is giving rise to alkaline fluids with hydrogen gas. Most hydrogen gas you find in planetary atmosphere are coming from serpentinization. , which is the mineral required for that... is ubiquitous in interstellar dust... So all of this pushes you down a certain avenue, and if that's correct it gives you bacteria... and if that's correct then bacteria have a structural problem, and they're not going to get beyond bacteria except with an endosymbiosis, and that in itself is improbable, unlikely... because it only happened once, to our knowledge, on earth.

No, we're not alone [in the universe]. We share it with lots of friendly bacteria [and this includes bacteria on other planets].