> > What is needed is a new theory that
> > incorporates both mono and poly into genesis.

One very distinct possibility is monogenesis (through elimination of
other lineages), but with the common ancestor not being what we
would call a proper language today. The ability to speak _may_ have
developed quickly, but is likely to have taken thousands of years to
spread. Note that grammar can diffuse, so there is a possible
synthesis - the ability to handle certain grammatical details, and
the exploitation of it, may have diffused ('monogenesis'), while
being grafted on to different languages ('polygenesis').