WASHINGTON -- California researchers are challenging 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 nerve complex needed to control the subtle and varied movement of the tongue required for speech.
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. responded Richard F. Kay, one of the Duke researchers.
Richard F. Kay, one of the Duke researchers, responded, "They've got an interesting point of view and it's stirring the pot."
"If their argument is taken at its 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 speculated 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, carrying the nerve that directs the tongue, is smaller in apes, which are incapable of complex speech, the Duke study found.
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 has been thought. Researchers have long believed that the ability to make modern human speech sounds did not develop until about 40,000 years ago.
While modern humans came along after the Neanderthal, some may have lived at the same time and place as the final generations of those early people.
DeGusta said his Berkeley group tested 30 nonhuman primates, compared to just two in the Duke study, and found 15 of them had hypoglossal canal sizes larger than humans.
"Because nonhuman primates are not known to speak, their hypoglossal canals should be smaller than those in modern humans," the researchers said. But "many nonhuman 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 close to humans.
According to the criteria of the Duke study, "modern human speech capabilities originated at least 3.2 million years ago in Australopithecus afarensis, a species not previously noted for (brain development), symbolic capacity or even stone tool making," they said. Australopithecus afarensis is the family of the famous African fossil Lucy.
He said 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 defended his group's use of average size by comparing studies of brain size in ancient and modern species.
Modern humans have a brain capacity of about 1,250 cubic centimeters, he said, 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," he added.