I’m sorry if my question isn’t particularly clear, it’s sort of hard to explain what I’m thinking. Most things that are alive have at least some sense of self preservation, and I understand the very basics behind it. For humans, it comes from being prey. However, why was it there to begin with? What caused us to have such a strong will to live? What causes self preservation for any species?
For a species to continue existence, it has to keep alive long enough to at least procreate. If some individuals are born without the instinct to survive while others are, it’s much more likely that those with the instinct will survive long enough to procreate and pass that trait to their offspring.
If that wasn’t a feature of life there wouldn’t be much life around. This is what we call natural selection. Beasts that do not have the self-preservation instincts are quickly erased from the gene pool. Reckless behavior in the wild is not an effective survival strategy, but being skittish or hyper aware of danger would be beneficial (depending on the environment).
So take an organism that doesn’t have it or is self destructive. It will die and fail to reproduce. This means only genes with this behavior is passed on. The stronger the instinct the better chance of being passed on. You see how this gets you to organisms that will do anything to survive.
Things that didn’t have self-preservation got itself killed while the things that did preserved themselves and lived. Things that are alive are much better at passing on their sense of preservation via their offspring, and so it gets spread around.
Avoiding death is a very good evolutionary trait.
Evolution selects for life that manages to reproduce the most successfully. Can’t reproduce if you’re dead.