The Japan Times, May 18, 1998
By HELEN PHILLIPS
Nature News Service
Nerve canal size suggests Neanderthals could talk
Spoken language was an important landmark in human evolution. Some argue that it is a uniquely human attribute that implies deliberate thought, self-awareness planning and collective decision making. Others take a cooler view and consider it just an extension of parrot-like mimicry and the communicative vocalizations of other animals. However important or unimportant the development, though, many people are interested in finding out just when we humans acquired the ability to hold a conversation.
New anatomical studies of fossils now suggest that speech may have evolved as long as 400,000 years ago. Some scientists believe that there is no definitive archaeological evidence for language earlier than about 40,000 years ago, but a new report, published in the Proceedings of the National Academy of Sciences, claims that the vocal capabilities of Neanderthal man were the same as those of humans today.
Dating the appearance of vocal capabilities is extremely difficult. Archaeological finds that imply group organization or symbolic behavior give some clues, but whether boat building, tool making or body painting require vocal communication or not can never be known for certain.
Anatomical developments that might indicate language abilities are very contentious. Some have tried to use jawbone structure or reconstructions of the vocal tracts to predict the sorts of sounds that would be possible. Others have tried to use measures of brain size and shape to infer the development of speech control centers.
Now Richard Kay and colleagues from Duke University Medical Center, Durham N.C. suggest a new anatomical measure that they believe is a much better indicator of vocal ability.
The ability to control the shape of the tongue is very important for producing different speech sounds. The better control, the greater the range of sounds. The researchers have now found an anatomical indicator of tongue control that is preserved in the fossilized remains of bones.
The tongue is controlled by a nerve bundle called the hypoglossal nerve (cranial nerve XII), which controls all but one of the muscles of the tongue. The researchers argue that a greater number of units in this nerve (basically, the bigger it is) implies finer control of the tongue shape for forming speech sounds. Therefore, the size of the hypoglossal canal, a bony channel at the base of the skull through which the hypoglossal nerve passes, should be a good indicator of nerve size, and hence an index of vocal complexity.
The researchers measured the size of hypoglossal canals of modern-day humans, apes and several hominid fossils. They found that the canals of modern humans are much bigger than those of modern apes, in both relative and absolute terms. Australopithecine fossils, and possibly Homo habilis, have canals no bigger than modern apes, suggesting that they had no more powers of speech than a chimp.
The canals of Neanderthals and "early modern" Homo sapiens, from as long as 400,000 years ago, are virtually identical to present-day human canals. The researchers conclude that "humanlike speech capabilities may have evolved much earlier than inferred from the archaeological evidence for the antiquity of symbolic thought."