The nerves that allow the tongue to make the sounds of speech may have developed in primitive, humanlike species some 300,000 years ago, long before the evolution of modern humans, researchers say.
In a study being published Tuesday in Proceedings of the National Academy of Sciences, researchers at Duke University report that the skulls of Neanderthals and of some other primitive higher primates show they may have had the nerve complex needed to control the subtle and varied movement of the tongue required for speech.Matt Cartmill of Duke, co-author of the study, said the bony canal carrying a nerve connection between the brain and the tongue is about the same size in the Neanderthal and early humans as it is in modern humans.
The nerve tunnel, called the hypoglossal canal, is smaller, however, in apes, which are incapable of complex speech, Cartmill said. The hypoglossal canal also is ape-sized in the skulls of Australopithecus, the primitives that could possibly have been the ancestors of early humans.
The nerve that goes through the hypoglossal canal controls virtually all the voluntary muscles in the tongue. Without such control, the tongue cannot perform the motions necessary for speech.
Researchers have long believed that the ability to make modern human speech sounds did not evolve until 40,000 years ago. The Neanderthal, whose remains have been found in Europe and Asia, evolved about 300,000 years ago. Modern humans came along later but may have lived at the same time and place as the final generations of the Neanderthal.
The two species differ in the shape and the size of the skull and skeleton. It is not clear if modern humans replaced the Neanderthal or if there was interbreeding between the two distinct species.
"If the size of that (hypoglossal) canal reflects the size of the nerve, and if the size of the nerve reflects the amount of coordination and control of the tongue, then the Neanderthal had a degree of control of the tongue resembling modern humans," Cartmill said. "Early hominids and apes did not. When we look at chimps and gorillas and early humans in Africa, they have much smaller canals."
Bernard Wood, the Henry R. Luce professor of human origins at George Washington University, said the Duke research "is an intriguing new line of evidence" about the speech abilities of the Neanderthal and of other primitive, humanlike species.
The fact that the hypoglossal canal in the Neanderthal is about like that of modern humans means that "it is a reasonable supposition" that the Neanderthal may have been capable of speech.