THE DIVINE SOURCE: In the biblical tradition, as described in the book of Genesis, God created Adam and "whatsoever Adam called every living creature, that was name thereof."
THE SOCIAL INTERACTION SOURCE: The sounds of a person involved in physical effort could be the source of our language, especially when that physical effort involved several people and the interaction had to be coordinated.
THE PHYSICAL ADAPTATION SOURCE: The types of physical features humans possess, especially those that are distinct from other creatures, may have been able to support production.
THE GENETIC SOURCE: Human offspring are born with a special capacity for language. It is innate, no other creature seems to have it, and it isn't tied to a specific variety of language.