Question

This might sound a little odd, but what is smell. It's specific atoms that make up a chemical to make a gas, but why does a specific atom end up creating a specific smell perceived by the nose of an organism (or any other form of smelling in an organism)?

Answer 1

good question...

Answer 2

Good question indeed! There are exposed neurons inside the nose that molecules will bind to, these neurons basically "look up" the molecule in your genetic dictionary. If a section of this DNA is damaged it can cause the individual to be unable to smell certain things. Humans have over (I think) 10,000 smells coded into their DNA.

Answer 3

Encoded in DNA? Are you suggesting that smells are inherited?

Answer 4

Yes, smells are inherited in the same sense that all our senses are inherited. DNA provides the instructions that build the sense organs so that they can relay interactions with the outside world to our brain. The genes provide the instructions for growing the olfactory receptor neurons and if one or more of those genes are damaged then we lack the ability to smell the associated molecules. Smell is the oldest sense dating back to the first animals over half a billion years ago and has evolved to include recognition for many many different molecular structures.

Answer 5

I see. The DNA determines which molecule type will bind to the olfactory neural-receptor. How do the neurons "look up" the molecule in the genetic dictionary? Doesn't each individual neuron map to a particular place on the brain?

Seems like that the association of a particular neuron-tickle (smell) with a particular object/memory would be a function of the epigenome.

Answer 6

Well thats just the association. When you are a baby and you smell your poop for the first time you dont say "Oh that's the smell of poop," you say "Oh that smells bad." And later in life you start to actually associate specific smells with specific objects. Evolutionarily this was because people who thought rotting carcases and feces smelled bad were less likely to eat/play with them and were less prone to disease.