Speech, originally, was the device whereby Man learned, imperfectly, to transmit the thoughts and emotions of his mind. By setting up arbitrary sounds and combinations of sounds to represent certain mental nuances, he developed a method of communication – but one which in its clumsiness and thick-thumbed inadequacy degenerated all the delicacy of the mind into gross and gutteral signaling.
Source:Part II. Search by the Foundation, Chapter 8. Seldon's Plan