So your saying we just vanish from reality or what.
Considering your brain is just electrical circuits, when you die the brain stops working and you wouldn't think anymore. You don't have a mind without your brain so you won't be aware your dead for the rest of eternity, you wont have any thoughts at all.
The leading scientific theory on how all life began is Abiogenesis:
Abiogenesis is the process by which a living organism arises naturally from non-living matter, as opposed to biogenesis, which is the creation of living organisms by other living organisms. Scientists speculate that life may have arisen as a result of random chemical processes happening to produce self-replicating molecules. One of the popular current hypotheses involves chemical reactivity around hydrothermal vents. This hypothesis has yet to be empirically proven although the current evidence is generally supportive of it.
There are plenty of theories on how the first cell started (none of which I am going to go into). We started through natural selection which is when only the species best suited for that environment survive. Example: there is an island with two types of birds of the same species, birds with long beaks and birds with short beaks, to get food on the island it is easier with a long beak. Eventually only the ones with long beaks would be the ones to reproduce because the ones with short beaks couldn't get enough food. Therefor only the genetics of the ones with long beaks would survive.
Using this process (which happens over millions of years), you could eventually get from something like a rat to something like a human by only having slightly human parts of each evolution survive. (ever heard how pigs have similar digestive systems to us? This is why.)
