"Emergent Property" is an ontological descriptive term of an observable end-result of a process requiring necessary observable or definable initial conditions AND observable or definable necessary praxiological operations on those conditions.  

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre

This two areas you describe are ver well known and do indeed perform certainly clear fucntions in language

But language processing , from writing to devleopment of sentences includes vast areas of the cortex not realted with those two.

Broca andd Wernicke are some kind of focal points  for the movement of the mouths/language physcial apparatus and for audotory input.

They are the most external parts of speech processing... something like the primary and final points of the process... Generally, the brain has very specific target areas before proceeding (or the first point of reception from external areas) to project activity to non-brain areas... moto cortex, visual priamry cortex and so on...

So, the ability to speak and process auditory cues comes from the ability of certain parts of the brain to do their primary fucntions by training. If you do not train those areas, they just mind their own business... and still it is only the surface of language processing since it is the part related with output-movement and input-auditory (people do nto know that but a fundamental part of speech is to understand auditory cues, this is why two areas are needed to link the external apparatus with the more complex language processing). But this is only the surface of the processing.. in the same sense the primary visual cortex is only the first stage of visual pattern recognition.

A pleasure

I therefore claim to show, not how men think in myths, but how myths operate in men's minds without their being aware of the fact. Levi-Strauss, Claude