Nasty survival of the fittest types
If the Universe is full of nasty survival of the fittest types who won their places by stomping out the competition, then yikes.
Do you want to tell him, or should I?
Do you ever wonder why you're not a marsupial? Or a reptile?
To be completely accurate, often it's more a matter of surviving something that kills the competition off, rather than direct attacks, but somehow I still don't think that having sex in the face of danger is a workable survival trait any way you look at it.