It is widely understood that the Earth formed around 4,600 million years ago, and life itself may have appeared as early as 4,300 million years ago.
The word early is key here. Based on how soon life appeared, and also based on how much longer it took for prokaryotes to become eukaryotes (~a billion years), it seems to be the case that life is pretty easy to bring about. The step from non-life to life seems to be much easier than the step from simple life to more complicated life.
Enjoyable and very clear post!
Yeah, even later origins (which usually are suggested to be around 3900 million years ago) are still pretty early which could totally suggest that life is almost an inevitability if the starting conditions are right. This is one of the reasons I'm pretty confident our very own solar system has plenty of unicellular life outside of Earth. And if panspermia has been indeed going on, then those lifeforms may end up being rather boring due to their similarities to terrestrial life! If multicellularity has also evolved, those creatures could be much more interesting.
Quite true.