California researchers are questioning a study that raised the possibility that Neanderthals could talk.
Duke University scientists reported in April that a bony canal in the skulls of Neanderthals indicates they may have had the nerves and anatomy needed to control the subtle and varied movement of the tongue required for speech.
But a paper appearing in Tuesday's Proceedings of the National Academy of Sciences questions that finding.
"The size of the hypoglossal canal is not a reliable indicator of speech. Therefore the timing of the origin of human language and the speech capabilities of Neanderthals remain open questions," said the team headed by David DeGusta of the University of California at Berkeley.
Richard F. Kay, one of the Duke researchers, responded by saying, "They've got an interesting point of view and it's stirring the pot. If their argument is taken at face value, we couldn't say humans have evolved toward having an increased brain size over the last million years," he said in a telephone interview.
The two studies have some similar findings but differ sharply in their conclusions.
The Duke study speculates that Neanderthals might have been able to talk based on findings that the average size of their hypoglossal canal was similar to that of modern humans.
The canal, which carries the nerve that controls the tongue, is smaller in apes, which are incapable of complex speech.
Neanderthals, named for the Neander valley in Germany where their remains were first found, evolved around 300,000 years ago.
If they could talk, it would indicate speech evolved significantly earlier than previously thought. Researchers have long believed that the human ability of meaningful verbal communication did not develop until about 40,000 years ago.
While modern humans came along after Neanderthals, some may have co-existed at the same time and place.
DeGusta said his Berkeley group tested 30 non-human primates, compared to just two in the Duke study, and found 15 of them had hypoglossal canals larger than humans do.
"Because non-human primates are not known to speak, their hypoglossal canals should be smaller than those in modern humans," the study reasons. But "many non-human primate specimens have hypoglossal canal areas that fall within the range of our modern human sample."
"The average gibbon's canal is twice as large as a modern human's," DeGusta said in a telephone interview, "so we suggest you cannot use canal size" to indicate the ability to speak.
Indeed the Berkeley paper notes that some very ancient hominids had average canal sizes similar to those of humans.
The Berkeley researchers concentrated on the range of canal measurements rather than their average, concluding that "an individual's ability to speak can depend only on its own canal size, not the mean size for its species."
Kay defnded his group's use of average size by comparing it to studies of brain size in ancient and modern species.
Modern humans have a brain capacity of about 1,250 cubic centimeters, though in some individuals it is as small as 800 cc. By comparison, the extinct species Homo Erectus a million years ago averaged about 800 cc, with some larger.
"You can say something from this average," Kay said. The Berkeley researchers contention that you cannot draw conclusions from averages means we "couldn't say humans have evolved toward having an increased brain size over the last million years."
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