Have you ever thought...

Have you ever thought what ever made you, who you are.  Why are you, you and not me? Why I am I not you?  Why am I a human and not an animal? Every living animal is alive and has existence.  They have thoughts to some extent, reactions, they sense pain and experience loss/hurt.  It is of interest to me though.  How is it that we are determined to be who we are and we cannot change that.  Is it our minds/brains that give us our being/identity or is it our soul? Almost any organ of the body can be exchanged and not change who a person is.  Is this true for the brain?  I also wonder is being a homosexual caused by a mind/soul/spirit mismatch with the body?  What do you think?