I'm going to bookmark this for the case someone asks: what piece of information that seems basic did you ignore until very recently?
A question that often arises is: if current life evolved from chemistry that's simpler than DNA, why has that one disappeared? Maybe it hasn't.
If that's the case, it was almost certainly because of the atmospheric oxygen.
Almost all of the chemical reactions that used to happen before it do not happen anymore on the wild.
Probably for the same reason we don't see relay or valve based digital computers anymore. They were outcompeted to extinction by their more sophisticated descendants.
The general thinking is that DNA evolved from RNA, which has certainly not dissappeared.
As to pre RNA chemistry, there is a good chance that the relevent chemicals still exist and are well studied. The issue is more that we have not worked out the specific proccess that led to the development of abundant RNA.
That sounds pretty cool for a hobbyist to potentially spend time on. Anything you could recommend to look at, for following up on this unknown stuff?
There's already a whole world of terrestrial microbes that we expect or even know for certain to exist but can't culture, let alone stain, which means we can't really study them. We'd (theoretically) eventually notice them on electron microscopy slides though, which is how we know there's many unculturable microbes, but whether we'd recognize them as alien is a completely different matter. The microbial world is very diverse and there's nothing I can think of that'd set something apart as alien since we can analyze the chemistry with an electron microscope.