What does "two becoming one flesh" refer to? In the Bible, when it refers to “two becoming one flesh”, does it mean that


the physical act of sex creates a position where both bodies are connected?


or


the flesh (DNA) from the man and and the woman unite to form one flesh (a child derived from both father and mother)?


or 


something else entirely?
St. Paul assumes the quote to be talking about the intercourse in 1 Kor 6, 16


  16 Or do you not know that he who is joined to a prostitute becomes one body with her? For, as it is written, "The two will become one flesh"