Supposing that we have two intelligent species arising on a planet at around the same time. They both are communal, both have the instinct to spread as wide as they can and build dwellings everywhere that they can, and both have some form of communication which allows them to convey complex ideas to one another. They both build dwellings in similar locations, creating potential conflict centered around availability of habitable land. However, these two species do not come from a common ancestor, and arose from mutually exclusive environments. As a result of this, they never had any interaction and their methods of communication became vastly different. For example, perhaps one species speaks at an audio frequency much higher or lower than the other can even hear. Alternatively one could speak while the other moves it's arms and emits smells as it's method of communication.
Supposing that these two species met in the early days of their development. Let's say that they are both at a similar technological level, just past the stone-age and getting into an equivalent to the bronze-age. What would be necessary for these species to coexist long enough to progress into, for example, the space age?
Though, to make sure I am being clear with what I'm asking. I want to know what would be the most common thing to happen in a situation such as this. If it is very unlikely for there to be a set or grouping of traits which allow for coexistence of these species, then I want to know. I can already answer what would happen if I were to define a particular set of behaviors for each species.