Comment by roughly

Two notes on this - one is that smell and taste are the earliest senses we have. The first thing organisms began to sense about their external environments were chemical gradients, and that’s in essence what smell and taste are doing.

The second is that what they’re doing is _fantastically_ complex from a physical standpoint compared to sight and vision - sight is the detection of photons of various wavelengths and energy levels; hearing is the detection of vibrations. Smell and taste are molecular docking problems: they are the detection and identification of the actual structures (or at least substructures) of molecules. The closest we have to that is mass spectrometry, which basically involves flinging molecules hard enough to break them and weighing the parts.