What is mistaken for closeness

My crude understanding of two very basic genetic concepts:

Mitosis: A process of cell division and replication where cells may identical copies of themselves to replace dying ones. This is how non-reproductive/germline cells reproduce - essentially by photocopying their genetic code into a new cell.

Meiosis: A process of cell reproduction where two different cells contribute a haploid of half of their genetic code for the formation of a new cell. This is how reproductive cells combine to create new cells and ultimately new organisms.

So when Andrew Bird sings that "we are all basically alone / despite what his studies have shown / what's mistaken for closeness is just a case for mitosis," he is probably bemoaning the fact that often two organisms come together and fail to create something new, opting instead simply to replicate the existing structures on which they previously relied.