In essence, we are also trying to preserve our existence, but we live in a complex and interconnected society. We aren't allowed to just do whatever we want to make that happen.
We first have to face the question of morality. It’s a set of principles, a body of standards or expectations. Essentially, a code of conduct. It is usually based around the ideals of kindness and equality. It determines appropriate behavior for humans. Morality is a construct that could unite humanity if it was universally uniform. Unfortunately, morality is not universal or static in any way. Throughout the world, what is deemed acceptable behavior differs greatly, and it usually also changes with time. In the past, the enslavement of the African-Americans was not viewed as a degenerate act of human cruelty. People understood it to be the natural order of the world. Only two years ago, women in Saudi Arabia could not be issued driver's licenses. Female genital mutilation has still not been made illegal in many countries. I think all of those things are clearly immoral, but that is because I live in a specific place at a specific time and have been taught that those things are not acceptable.
The difficult thing about morality is that it not only differs historically and culturally, but also different from one family to the next, and then even a little in each member of said family. It is a deeply nuanced and personal thing. Each little experience that creates who a person is by creating how their mind works, is also creating their morality.
Humans’ concept of morality comes out of their ability to analyze how their actions will affect the world around them, and the learned feelings attached to the results of their actions. We make choices based on feelings, and those feelings are there because we have been taught to feel that way. Essentially, humans have programming. The beautiful human mind is very powerful but also very malleable. An argument could be made that raising a child is programming a human being. We only know things are right or wrong because we were told, explicitly or inexplicably, that that was the case. So, morality and the mind cannot be separate. Morality is something that exists in the mind, because of the mind. It is part of a human being.
The natural world has no need for the concept of morality. It has a cycle and a balance of power. It doesn’t need morality. It may seem sad or cruel, but if an animal is born in the wild with some sort of defect it is very unusual that it will survive. It will usually end up being eaten by a predator, and while the idea of some little fawn born with crooked legs by no fault of its own, ending up as the meal of a coyote is a sad one, it is absolutely necessary. It preserves the strength of a species by eliminating the unfit. It isn't cruelty or immorality, it is the natural cycle of life. It’s how the cycle of life works and the world balances itself. Morality and immorality wouldn’t exist in a world without humans, because morality is human.
Humans need the guiding principle of morality as a result of the disproportionate power and complexity of our species. Our existence has become too complicated and interwoven to live without it. It is not possible to just live for yourself and your offspring, unless you live in some remote part of Russia and never make contact with another human being perhaps. We now have to make decisions that affect much more than just our lives and the lives of our offspring. Humans are asked all of the time to make decisions that concern a whole town, an entire country, or even a species. We are very lucky to have the amazing minds we do, and it's very lucky that morality gets “programmed” into brains because it is a wonderful asset and maybe, just maybe, one day we will all settle upon a common definition and humans can be united in an understanding of what is good and just for all.