THE HYPOGLOSSAL CANAL AND THE ORIGIN OF HUMAN VOCAL BEHAVIOR

The mammalian hypoglossal canal transmits the nerve that supplies the muscles of the tongue, This canal is absolutely and relatively larger in modern humans than it is in the African apes (Pan and Gorilla). We hypothesize that the human tongue is supplied more richly with motor n erves than are those of living apes and propose that canal size in fos sil hominids may provide an indication about the motor coordination of the tongue and reflect the evolution of speech and language. Canals o f gracile Australopithecus, and possibly Homo habilis, fall within the range of extant Pan and are significantly smaller than those of moder n Homo, The canals of Neanderthals and an early ''modern'' Homo sapien s (Skhul 5), as well as of African and European middle Pleistocene Hom e (Kabwe and Swanscombe), fall within the range of extant Home and are significantly larger than those of Pan troglodytes, These anatomical findings suggest that the vocal capabilities of Neanderthals were the same as those of humans today. Furthermore, the vocal abilities of Aus tralopithecus were not advanced significantly over those of chimpanzee s whereas those of Home may have been essentially modern by at least 4 00,000 years ago. Thus, human vocal abilities may have appeared much e arlier in time than the first archaeological evidence for symbolic beh avior.