How much do experts understand about the nature of instinct in animals and in humans?

How does it operate? Is there a certain part of the brain it comes from?
For example, how does the memory of an elephant work? How does it map places it has been in its mind and know how to return to those places? Does it work the same as in birds returning to their roosts and other animals that return to the same breeding ground every year?

Do humans have instinctual behavior too?
I was wondering if Xenophobia (fear of outsiders and foreigners), and the fear of those who are just different than we are, is instinctual?
I came to this question because I have that song from South Pacific stuck in my head!! You’ve Got to Be Carefully Taught
Is that true? Or is there an element of instinctual fear that needs to be socialized out of us? Is there any sort of “collective memory” in humans? Maybe we need to be taught how not to hate and how not to bully.

Last question-How can I get that damn song out of my head now??