Bad Smells: Nature or Nurture?

I used to wonder what makes a bad smell revolting. A bad smell doesn't do you any harm just because it smells foul. (If it does do you harm, it's not because of the smell, but from some demonic compound in it.) So what makes us wrinkle up our noses and run away? Nature or nurture?

I used to think it was nurture. When raw meat scraps have been in the kitchen trash too long, Mom says "Gross!" and so Little Tyke gets the subconscious message: I'm supposed to think that smells bad. And so he grows up thinking that garbage smells "bad" and flowers smell "good."

But do pets agree?

To support this initial hypothesis that smells are a function of upbringing and conditioning only, along came my Australian Shepherd/Border Collie mix. Now our neighbors kept lots of livestock and pets. It just so happened that one of these creatures expired and was buried on the edge of an open field facing our house, about 150 yards distant. Unfortunately, this poor blighter received a burial that Antigone would have found only slightly better than her brothers': it was crammed in a shallow and highly accessible grave. In fact, nearly half of its carcass was constantly exposed and apparently giving off an exquisitely putrid odor.

My dog went to town. In nearly all of her free time (24 hours a day), she would sneak over to the Field of Death and plunge her face into the long-dead corpse, pulling, chewing, and who-knows what else. Needless to say, it was not a few times when my face-to-face cuddlings with her were stopped brutally short due to a massive wall of Smell that sent me into paroxysms of retching and choking.

My dog loved the smell. I despised it. What better proof for nurture could there be?

But it was a false conclusion. Smells are bad just because. Why? Because of the trump card: my cat.

Initially, this noble feline, along with my dog, would display no signs of disgust at the usual smells that humans consider putrid. Smelly garbage? Flatulence? Not a problem. If anything, my cat loved it. So far, dog and cat agree.

But one night as I was brushing my teeth, the cat became enthralled with the motion and sound of my brushing. In fact, she even readied herself to pounce. She crept closer, and I squatted down to accommodate her curiosity. She came closer and closer until she stopped short . . . and began squinting. Cringing. Flinching. I was fascinated. I exhaled slightly on her face. She squinted, shook her head confusedly, and slunk away.

She did not like the smell.

My initial theory was therefore debunked. An animal might not mind certain smells that humans hate for various reasons, but if an animal hates any smell (regardless of human opinion), then we have a strong case for Intrinsic Foul-Smellingness. Some smells, deep down, in their heart of hearts, are just bad.