Mutations in DNA can have a positive or negative impact on the ability to reproduce. Because of natural selection, positive mutations tend to be preserved while negative mutations tend to disappear. There is no intent behind this process; it is simply a consequence of how life works.

While we can't yet say for certain how life got started, it is likely that the first "life" was made up of self-replicating RNA. Because this RNA self-replicated and produced imperfect copies, it was already undergoing evolution at that point, where the RNA strands which were better at copying themselves (due to mutations) were more plentiful.

I understand it doesn’t seem intuitive at first, but evolution is actually quite similar to that.

> Trees produce thorns to keep away animals.

It's not that trees consciously produce thorns to keep animals away. Rather, trees with thorns (due to random mutations) are more likely to survive because they are less likely to be disturbed by animals. Over time, those trees are more likely to reproduce and pass on those traits.

Just like water flows down the path of least resistance, evolution naturally selects for traits that improve survival. The "selecting" we are referring to is used in the same sense that water "selects" which route it takes. It doesn't actually select anything, it's just following the laws of physics.