Loved this post! Wished there were more posts like this written by by domain experts: short, succinct (no jokes, unnecessary examples), leads to many interesting thoughts on the subject and has clear references.

The fact that smell works so differently than our color perception is very interesting to me. Color perception is mathematically so neat to analyze: there are 3 or more (in some animals) basis functions corresponding to receptors and you build on that. I wonder why smell didn't evolve like that but developed so many different types of sensors. Probably the fact that it evolved much earlier is a factor (the more elegant solution was not hit upon by Nature) or maybe there is some other reason (important smells also evolved but all colors were available for training from day 1).

The phrase "the latest research seems to suggest that humans can smell up to 1 trillion different scents" is interesting since it treats smells as discrete entities, while you can't do the same with colors since they gradually change from one to another with no boundaries.