What? Can you expound on that statement a bit? Relative to what, the age of the universe?
Well, no, not the entire universe. I meant "recent" relative to our biological development as human beings -- hundreds of thousands of years perhaps. Human biology hasn't changed significantly in the last say ten thousand years, but that was the rise of civilization.
It was only when humans started putting together the traditional family that we advanced towards civilization as a species. And marriage was developed as a protection of that traditional family structure. The Seventh Commandment was God's directive to make that official, in my opinion.
The above is of course just my own belief of how things went. YMMV. :)