In my words: evolution of the species is an interesting phenomenon. When a new “invention” is tested, it does not replace the original organ, so in case it doesn’t hit the mark, and isn’t better, it doesn’t set back the entire species.
This is especially true with organs that are mandatory for life, like the brain.
According to this hypothesis (not a fact!) the human brain has three detectable stages that grew on the top of each other and are still functional, therein lies the problem.
The reptilian brain that is selfish, reactive, and knows only a few tricks, eat, shed, fight or flight.
The mammalian brain where we have our emotional (limbic) center… why? beats me… I guess mammals have emotions?
And the frontal cortex, where all higher function is performed, especially choice.
Unfortunately to us, our lowest has a tendency to run our lives…
The reptilian brain has a strong connection (maybe just seemingly) to the subconscious, or other than conscious mind..