I think that it would have massive implications on how human society and instincts developed. For one thing, a massive amount of information can be gleamed about a person's emotional state, physiology, and intentions from an analysis of their smell. This is why certain species (dogs, for example) can almost appear to have a "sixth sense" and be able to detect when a person is under emotion distress or about to suffer from physiological problems (like an illness). In many cases the changes in chemical composition give away the internal state of the person.
It would not be unreasonable to assume then that if humans had an advanced sense of smell then they would rely upon more nonverbal cues in their language (including olfactory ones - it would be far hardly to overtly lie when your chemical signature gives you away, for example), be less inclined to enjoy purely visual entertainment as they interpret their world mostly through smell (it would be harder for them to relate to anything on a television screen, as the lack of discernible smells would constantly indicate to them that what was on the screen isn't real; perhaps they would be more inclined towards live theater instead?), and would have a significant portion of their education (formal and otherwise) on using their advanced sense of smell.
Additionally, since the sense of smell is directly tied into the limbic system (the seat of emotional response and emotional memories) it would be expected that we might be more emotionally driven by our olfactory environment, which would undoubtedly be exploited in order to make populations more amicable for certain actions. This would be especially pronounced in that our sense of smell is "wired" differently in the brain, with the smell being interpreted in the olfactory bulbs and yielding an emotional response in the limbic system before it is processed by the olfactory cortex. This is part of the reason that we have difficulty breaking smells down into their components, whereas we can do this with our other senses. For example, we can see that a painting may have red, blue, and violet paints which combine to form a representation of an object, but we would have difficulty in determining what basic smells combine in order to make up the composite smell of freshly baked chocolate chip cookies. In the same manner that visual cues are used in propaganda and advertising in order to effectively manipulate people, the smells in certain locations could be modified to yield similar (and probably much more effective) results.
Goodness, that was a long answer. :blink: To summarize, if humans had a well advanced sense of smell it would affect a lot of things.
What if humans learned language in the same manner as certain bird species learn songs, where they could only learn new words and grammar during certain times of the year?
