I've traveled in a lot of developing countries. I imagine many of the smells I've encountered in small cities are the same as they've been for centuries or even

I've traveled in a lot of developing countries. I imagine many of the smells I've encountered in small cities are the same as they've been for centuries or even millenia. The most prominent smells are sewage (from open sewers and natural waterways loaded with sewage); agricultural (manure from both farms and from animals still used in transport); and burning garbage (still common in many rural developing areas). The biggest shift is likely the replacement of manure from transport animals (horses, oxen, etc.) with unregulated exhaust from transport (trucks to be sure, but primarily from two-cycle engines on small motorcycles and tuk-tuks). I can't imagine what a large metropolis would have smelled like before sewage was largely contained and before internal combustion engines replaced animals.