It's pretty much *scientifically understood by now that our brains were "designed" (if you want to use that word) in such a way that we have no choice BUT to think about sex on a regular basis. The brain also synthesizes an addicting sensation to orgasms, so that we seek them out and the species consequently thrives. While it synthesizes disfavourable sensations (in this case smell) to, say, the molecules typically present in decaying food - so that we avoid them, and the species thrives. As far as I know, there's no smell property inherently imbued in molecules - it comes from the brain. Anyway, for the religious: Us being slaves to the construction of the human brain - why would a perfect deity design us inherently flawed (so that we can't help but think of sex regularly) and then proceed to punish us for it? That's kind of like taking meth all through your pregnancy and then beating the shit out of your kid every day as punishment for him being born mentally retarded. No, in fact that analogy isn't even sufficient in capturing just how unspeakably cruel God must be, if he exists. In this analogy, the mother's actions weren't as direct and intentional as God's must have been (just, for example by the fact that she's not omniscient, although she'd have to be an utterly despicable person) - and the punishment is not eternal. And yet God supposedly loves us with a love so great it's beyond our comprehension. You'd definitely be right about it being incomprehensible. Non-sensical is a better way of putting it. If God were a citizen he'd be in prison for child abuse and a candidate for "worst parent of the century". If God's real, he must be an exceptional fuckwit.
*This is really just my philosophical speculation. I know nothing about biology. Makes sense to me, anyway.