Primitive life just happened. Our predecessors climbed out off the primeval ooze and evolution took over. Chances are that mankind will evolve further before our inevitable extinction.
Not everything needs a reason to happen, some things just exist.
Why should we care? As individuals & a world we will live and die in a blink of space/time, then we know nothing.
The star Betelgeuse has been seen to dim a little - possibly preparing to become a super nova. But it is 700 light years away, so it may have blown up and disappeared 500 years ago but mankind won't know that for another 200 years.
there is a natural tendency for some elements to form complex structures, then on to complex molecules and replicate until there is life. As for the universe itself, it, or at least the bit we are aware of, was the ultimate "free lunch" as one of the bits that usually pop into existence and go out again, exploded instead, as uncertainty says it must at some point. It's possible so will happen.
I don't know, but the answers above all make some sense at least.
If we are assuming we started with nothing, where did God come from? And why is it more believable that a god materialised, than a couple of cells that reacted together?
I would say the same thing as I do now, which is I don't know and does it matter? What matters is right here right now (and I am sure that many if not all religions say something similar) we can be kind, protective of the weak, honest, loving and thoughtful without having a scooby about our origins.
I don't think I have had an answer from you to that particular question- and the last thread I just scanned through, seemed to come down to "work it out yourself".
Good question and no-one knows if we came from nothing or not. There is a limit to our human cognition, maybe that threshold could continue to increase as (and with) our knowledge has historically increased: or increase through genetic manipulation, human machine integration, a mixture of both of those, or by some other factor.
Aliens or entities with larger brains or different but larger capacities of comprehension may look on us with our 'limited' capacities of comprehension as we look at cockroaches and see them with far less cognitive capacity than us.
As Dirty Harry said, " a man's got to know his limitations.