We even have evidence of life we have never seen, will never encounter, and may never even have conceived as being possible to exist without that evidence: the enormous dinosaurs.
Look, humans already adapted to being in space for prolonged periods of time. We adapted to every climate. But drop a naked human in a random spot on our planet, and he will die with high degree of probability. And that's after billions of years of evolution.
Who knows if this jump alone should be taken for granted - plus, not many planets could provide 3 billion years of "good weather" (or staying habitable) to start with.
We might be a slow developer and poor representative sample in that respect, but without more data it's hard to tell.
> plus, not many planets could provide 3 billion years of "good weather" (or staying habitable) to start with.
I suspect the opposite will be true, red dwarfs are the most common type of star and are stable for trillions of years. Even if the average time it took multi cellular life was 30 or 300 billions years then it might not matter for life evolving there. They do come with some other caveats though: https://en.wikipedia.org/wiki/Red_dwarf#Habitability
Lewis Wolpert : https://link.springer.com/chapter/10.1007/978-3-0348-8026-8_...
Life on Earth evolved and spread under specific conditions - our gravity, sun brightness, geology, magnetic field, large moon, etc etc. It then spread to all possible environments on the planet and evolved to live there.
Unfortunately, it could be that the 'growth conditions' for life are quite specific even if - once it gets going - life can evolve to more general environments.
But all lifeforms we know evolved from one common ancestor, it's one tree of life. As far as we know life evolved here only once.
So we know that once life happens it can become completely ubiquitous, but it doesn't say anything about that crucial first step.
That's not nessisarily true. Single celled organisms have a rather fluid exchange of genetic information even our 'single cells' are really several different organisms. It's possible life evolved many times on earth and current single celled organisms and thus all life has a mismatch of ancestors.
Further, life may regularly evolve even today, but simply get eaten due to the stiff competition.
PS: We know life evolved at least once, but the high end could be multiple times a second on earth.
It's also possible it evolved elsewhere and rode here on a meteor - or was brought here by some other lifeform several orders of magnitude more advanced than us, using earth as their own cosmic terrarium.
It's good practice to assume the simplest possible solution. However, the full range of the full range of what might have happened is ridiculously large.