I have a simple question: how does subjectivity arise?

By which I mean, why am I me as opposed to anyone else, or any thing else? Why am I this body of matter rather than another body of matter? Why am I ANY body of matter? And furthermore, if molecules are continuously swapped in and out of my cells, and cells are replaced, then how am I still seemingly existing as this body of matter? How am I seemingly experiencing a smooth flowing transitional experience from conception to death? It may be a slight understatement to say that this is a simple question. Only a slight understatement.