smell is the first sense, pretty much. single-celled organisms already have it.
of course, in some ways, it’s not as easy as for example vision. you need 3 different kinds of photoreceptors to see pretty much all that there is to see, but you need god knows how many chemical receptors in your nose (or all over your cell wall in the case of bacteria or the like) to sense all the interesting stuff floating around.
smell is the first sense, pretty much. single-celled organisms already have it.
of course, in some ways, it’s not as easy as for example vision. you need 3 different kinds of photoreceptors to see pretty much all that there is to see, but you need god knows how many chemical receptors in your nose (or all over your cell wall in the case of bacteria or the like) to sense all the interesting stuff floating around.