The Duke scientists, Richard F . Kay, Matt Cartmill and Michelle Balow, focused their study on a tiny pencil-size tubular bone at the base of the skull called the hypoglossal canal.
22.
And the much smaller hypoglossal canals in earlier fossil hominids, known as Australopithecus africanus, were almost identical in size to those of modern monkeys, chimpanzees and gorillas, the Duke scientists found.
23.
Another early true Homo sapiens skull, found in Israel near the Kebara site, is probably about 110, 000 years old, and it also had a hypoglossal canal the size of modern humans.
24.
But in 400, 000-year-old fossils of the Homo line, the hypoglossal canals fell within the size range of modern humans and thus could have carried enough nerves for tongues to form speech sounds.
25.
His team's research, which shows no correlation between canal size and speech potential, shows there are a number of extant non-human primates and fossilized australopithecines that have an equal or larger hypoglossal canal.
26.
The upper surface of the lateral part presents an oval eminence, the jugular tubercle, which overlies the hypoglossal canal and is sometimes crossed by an oblique groove for the glossopharyngeal, vagus, and accessory nerves.
27.
The Duke approach of comparing the size of the hypoglossal canals in the skulls of Neanderthals with modern humans, with monkeys and apes, and with far more ancient hominids " just doesn't provide good evidence for the origin of speech,"
28.
The nerve arises from the hypoglossal nucleus in the brain stem as a number of small rootlets, passes through the hypoglossal canal and down through the neck, and eventually passes up again over the tongue muscles it supplies into the tongue.
29.
David DeGusta, W . Henry Gilbert and Scott P . Turner contend in their research report that they have " falsified " the Duke theory that the size of the hypoglossal canal and its nerves is an indicator of speech and language capacity.
30.
On the basis of comparative measurements of hypoglossal canals of modern humans, apes and several human ancestor fossils, the researchers concluded that the canals of modern humans are almost twice as large as those of modern apes _ the chimpanzee and the gorilla _ which are incapable of speech.
