Washington, July 9 : Scientists studying the structure of the ear canal of 530,000-year-old prehistoric human skulls have suggested that human speech may have originated earlier than some researchers contend.
The study is the first to use a fossil to reconstruct sensory perception in any Homo species.
According to a report in Science News, the skulls were found at the Sima de los Huesos site in Atapuerca, Spain.
"Anthropologists disagree about whether language sprang up rapidly around 50,000 years ago or emerged more gradually over a longer period of time," said Rolf Quam, a paleoanthropologist at the American Natural History Museum in New York and coauthor of the new study.
The auditory bones of the 530,000-year-old skulls indicate that an early human species called Homo heidelbergensis may have heard sounds much the way people do today.
H. heidelbergensis are thought to be an ancestor of Neanderthals, a fact due to which the debate about whether Neanderthals could speak or not could reignite.
Researchers have long tried to determine whether Neandertals could speak by reconstructing their vocal tracts, according to Quam. But soft tissue makes up most of the voice box, so few traces remain in the fossil record.
The ear is a better candidate because the bony structure reveals more about hearing capacity.
The Atapuerca research team, which includes members from many disciplines and universities, used CT scanning of the skulls to reconstruct the size and shape of the ear canals, according to Quam.
Like in modern humans, the ear canal of H. heidelbergensis had a peak in auditory sensitivity in the frequency range from 2 kilohertz to 4 kilohertz, where much spoken information is transmitted.
"The length of the ear canal determines what frequencies of sound waves resonate, and are therefore heard more easily," said Sunil Puria of Stanford University, who models hearing patterns from ear structure.
The geometry of the ear canal revealed that the hearing patterns of H. heidelbergensis overlapped with those of modern-day humans.
Both modern people and the ancient hominids have especially sharp hearing in the 2 kilohertz to 4 kilohertz frequency range, where much of the sound energy of spoken language is transmitted.
According to Coleman, if H. heidelbergensis did have modern hearing capacity, however, it's logical to assume they had a primitive form of human communication.