http://news.sciencemag.org/sciencenow/2011/02/do-vibrating-molecules-give-us-o.html

Smell has long been explained by the “lock and key” hypothesis, which holds that we smell when odor molecules—each with a particular shape—“lock” into matching smell receptors in the nose. What’s the problem with this hypothesis? The fact that there are only a few hundred of these receptors in the human nose, yet humans are able to detect thousands and thousands of different odors.

So how exactly do we smell, then?

Researchers at MIT are looking now at the role vibration plays in our ability to sniff stuff out. They believe that the reason certain odor molecules can have similar structures (like vodka and rotten egg odors, apparently), they have radically different vibration properties, which may be the key to our being able to differentiate between so many different odors with so few receptors.

The MIT scientists performed experiments with fruit flies in which the flies were placed into a maze into which two nearly identical odor molecules were pumped. Despite the molecular similarities, the flies showed preference to one odor over the other, indicating that they could tell a difference between the odors—a difference the scientists say is due to different vibration patterns.

While this study doesn’t apply to humans necessarily (obviously), the scientists are looking to extend its results to tests with mammals.

Because I’m me, I wonder how figuring out how smell really works would play into treatment for anosmia and parosmia. If at all. You never know, biology is weird.