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Homo neanderthalensis

The discovery in 1989 of the (Neanderthal) Kebara 2 hyoid bone suggests that Neanderthals may have been anatomically capable of producing sounds similar to modern humans. The hypoglossal nerve, which passes through the hypoglossal canal, controls the movements of the tongue, which may have enabled voicing for size exaggeration (see size exaggeration hypothesis below) or may reflect speech abilities.

However, although Neanderthals may have been anatomically able to speak, Richard G. Klein in 2004 doubted that they possessed a fully modern language. He largely bases his doubts on the fossil record of archaic humans and their stone tool kit. Bart de Boer in 2017 acknowledges this ambiguity of a universally accepted Neanderthal vocal tract; however, he notes the similarities in the thoracic vertebral canal, potential air sacs, and hyoid bones between modern humans and Neanderthals to suggest the presence of complex speech. For two million years following the emergence of Homo habilis, the stone tool technology of hominins changed very little. Klein, who has worked extensively on ancient stone tools, describes the crude stone tool kit of archaic humans as impossible to break down into categories based on their function, and reports that Neanderthals seem to have had little concern for the final aesthetic form of their tools. Klein argues that the Neanderthal brain may have not reached the level of complexity required for modern speech, even if the physical apparatus for speech production was well-developed. The issue of the Neanderthal's level of cultural and technological sophistication remains a controversial one.

Based on computer simulations used to evaluate that evolution of language that resulted in showing three stages in the evolution of syntax, Neanderthals are thought to have been in stage 2, showing they had something more evolved than proto-language but not quite as complex as the language of modern humans.

Some researchers, applying auditory bioengineering models to computerised tomography scans of Neanderthal skulls, have asserted that Neanderthals had auditory capacity very similar to that of anatomically modern humans. These researchers claim that this finding implies that "Neanderthals evolved the auditory capacities to support a vocal communication system as efficient as modern human speech."