I think the most interest question in this early biology is why LUCA is so complex [1]. We have a massive gap between abiotic processes and the first organism we know anything about. What happened.
"Before high fidelity replication, organisms could not be easily mapped on a phylogenetic tree. Not to be confused with the Ur-organism, however, the LUCA lived after the genetic code and at least some rudimentary early form of molecular proofreading had already evolved. It was not the very first cell, but rather, the one whose descendents survived beyond the very early stages of microbial evolution."
And the question that fascinates me is "where are these primitive forms"? Even if the original forms evolved since, why can't we find at least some "improved" forms that use these more primitive principles than the ones we're accustomed to?
It can also be we'll never know, as the life on Earth apparently existed for so long, billions of years, since the times the whole Earth was completely different than we know now (from the life's point of view).
Which is also fascinating, as on the Universe level we can actually observe the glow of the Big Bang, which happened much earlier.
What are our chances of finding any of them?
This is a really good question. It is possible that some of these primitive lifeforms still exist (deep underground would be my best guess) but for technical reasons we can’t easily find them.
We have two basic ways of find living microorganisms: 1. We can either grow them in culture, or 2. We can look for genetic markers that can be amplified using techniques like PCR. If these primitive micro-organisms grow slowly (say divide once a year) then we will never find them in culture (we already know the microorganisms that live deep underground grow at this sort of speed). The genetic marker approach requires that the primitive organism have the same genes as all modern organisms (ribosomes normally). If they don’t have these genes then we won’t find them using our current approaches - they could be there and we just miss them.
If I was Bill Gates rich I would spend some of my money sponsoring deep earth microbiologists to look for cells that appear to be maintaining an energy gradient, but which don’t have ribosomes.