Originally Posted by SchrodingersCat
I saw a show about that on Discovery once, on that series they had about Sex.
This one has a much simpler explanation: a man who produce more sperm when seeing his mate with other men has a better chance of competing with their sperm, thus increasing his own chances of reproducing.
The same effect happens when a man's mate goes on vacation. His body assumes she spent the time away mating with other men, and so his body jacks up the sperm production in order to compete.
Yes they mentioned that holiday thing also in S@D.