Religion

"manifested" from an egg from your mom fertilized from the sperm from your dad.
It grew in your mom's belly thanks to nutrients provided by her.

That then led to your brain and the rest of your organs and parts as that fertilized egg grew and followed the plan of the DNA inside of it.

Your brain then "manifested" your mind.
Because your brain was still massively underdeveloped, so was your mind...to start. So much so that from 0-1 or 2, dogs and cats are more sophisticated and intelligent and aware.

Then you grew, and your brain grew and thus your mind grew until roughly the early 20s when the brain, more or less, stops developing (of course there are some small changes for good and for ill that continue on over life but nothing approaching ordinarily what happens during this 20+ year development cycle).

It's why most of us more or less are who we are by our late 20s barring something significant.
It's why significant damage to the brain fundamentally changes our personality and sense of self.
It's why being born with just a brain stem leads to no cognition or sense of self.
"You" requires your brain. If you change your brain, you change "you." Look at what happens to lobotomized people.
If your brain doesn't work right, your mind doesn't work right. See e.g. chemical imbalances and mental illness or amygdala size and schizophrenia.

So, your mind needs your brain. Without a brain, you don't have a mind. A dysfunctional brain means a dysfunctional mind.

It's not rocket science (although I suppose it can involve brain surgery).