"While language can surely be used for communication (as can much else), communication probably has no special role in its design or evolution."

Previous Quote

Language would have evolved first as an internal object, a kind of "language of thought" (LOT), with externalisation (hence communication) an ancillary process. I can't review here the strong and growing evidence to support this conclusion, but I have elsewhere. There are ample reasons why having a LOT would confer selectional advantage: the person so endowed could plan, interpret, reflect, etc., in ways denied to others.

— Noam Chomsky