For the last half-century study of the functioning of language has taken two separate forms. The first has been an abstract purely linguistic approach mainly but by no means solely associated with Noam Chomsky. The second has been the application of the increasingly powerful techniques of neuroscience to the functioning of language in the brain. With the use of PET, fMRI, MEG and ERP to track brain operation, as well as aphasiological and lesion research, there is now a very substantial body of physiological evidence which has eventually to be synthesised with the large accumulation of material from linguistics - or perhaps to be used incidentally to demonstrate the inadequacies of much linguistic theory. If the language capacity of humans has to be recognised as a product of the evolution of the human brain and not a purely conventional and cultural phenomenon (the Saussurean concept), then language has to be examined as a facet of brain function with necessarily direct links with perception and motoric activity. This paper presents an account of recent neuroscience research which bears on two key aspects of the motor theory of language origin and function: the existence of motor primitives and the significance of motor equivalence. Motor equivalence (a term originated by Karl Lashley) means that the same high-level motor programs can be executed by different muscle/joint assemblies. Motor primitives are elementary action-units instantiated in the CNS which make possible the construction of complex action- sequences and overcome the otherwise insuperable problems associated with multiple degrees of freedom. The motor theory of language proposes that there is a direct relation between speech (as action) and the motor primitives found for other forms of action and that speech as a motor activity can be accounted for in terms of motor equivalence.