Q; WHY left hemisphere language?

[JCCampbl]

It is news to me that all language arises from the left hemisphere and
trauma forces it to the right.  Better check with your profs.  What is
known is that children who have one hemisphere removed (or damaged in some
ways) can develop functions using the other - including language.  This is
due to the plasticity of the young brain.  That is, you learn by creating
an over abundance of neural connections.  Some of these are used, some
aren't.  Those that aren't are "pruned" - die off.  Now - why the
left--well there is an asymmetry in the skull that creates a little extra
space of a bit of matter though to be very important to learning language.
 But how did that get there.  Well, there's an interesting book called the
"Throwing Madonna" - if memory serves me correctly.  The central theme is
that early humans and primates held the young to the left side freeing the
right for throwing creating an asymmetry... who knows... young might also
look at the work of MacNeilage, and a very nice bood from NATO on face
processing.  Other authors - Brown (microgenetic theory) - any of the
aphasia people - Kuhl, Green, Chomsky, - well, it gets long and heavy. 
Good luck.