chris rollston has written a solid article on the probable inventors of the alphabet on the asor blog. he concludes:
(1) the Muttersprache of the inventors of the alphabet was a Northwest Semitic language, (2) and that the inventors of the alphabet functioned in a reasonably high status role within a component (or components) of the Egyptian administrative apparatus, that is, officialdom. (3) I believe that it is reasonable and tenable to argue that they learned Egyptian writing from Egyptian scribes. (4) I contend that it would be improbable that illiterate miners were capable of, or responsible for, the invention of the alphabet. (5) Ultimately, writing in antiquity was an elite venture and those that invented the alphabet were Northwest Semitic speakers, arguably they were officials in the Egyptian apparatus, quite capable with the complex Egyptian writing system.
give it a read.