By Tia Ghose
July 7th, 2008
Web edition
Fossil finds suggest an early origin for human speech
ALL EARSCT scanning of H. heidelbergensis skulls, like the one shown
here, helped a team reconstruct the structure of the ear canal of this
Neandertal ancestor. The skulls, more than 530,000 years old, were
found at the Sima de los Huesos site in Atapuerca, Spain.Quam et al
It may be time to rethink the stereotype of grunting, wordless
Neandertals. The prehistoric humans may have been quite chatty — at
least if the ear canals of their ancestors are any indication.
The findings suggest human speech may have originated earlier than
some researchers contend. Anthropologists disagree about whether
language sprang up rapidly around 50,000 years ago or emerged more
gradually over a longer period of time, says Rolf Quam, a
paleoanthropologist at the American Natural History Museum in New York
and coauthor of the new study.
The auditory bones of 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 Neandertals. The findings could reignite debate about
whether Neandertals could speak, Quam and colleagues report. The study
is the first to use a fossil to reconstruct sensory perception in any
Homo species, they add.
The skulls are from a site in Atapuerca, Spain called Sima de los
Huesos, or “pit of the bones.” 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, Quam says.
CHART
NOT HARD OF HEARINGLike in modern humans (shown in solid blue), the
ear canal of H. heidelbergensis (shown in red and magenta lines) had a
peak in auditory sensitivity in the frequency range from 2 kilohertz
to 4 kilohertz, where much spoken information is transmitted.
Chimpanzees (shown in solid green) have a dip in sensitivity in that
range. Quam et al
The length of the ear canal determines what frequencies of sound waves
resonate, and are therefore heard more easily, says Sunil Puria of
Stanford University, who models hearing patterns from ear structure.
The geometry of the ear canal reveals 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.
Chimpanzees, the closest living relatives of Homo sapiens, by
contrast, have a dip in sensitivity around 4 kilohertz, says Mark
Coleman of Midwestern University’s campus in Glendale, Ariz. Coleman
studies primate hearing but was not involved in the study. “Of course
primates can differentiate sounds related to speech — so can my dog —
the key is that humans appear to have a maximum sensitivity in the
range that contains a lot of overtones in speech.”
The results don’t necessarily show that the ancient humans could
speak, Quam says. “We're saying that the ear changed for some reason
and that those changes facilitated the possibility of language
development,” he says. The team reported the findings July 3 in Paris
during the Acoustics ’08 conference.
Researchers have long tried to determine whether Neandertals could
speak by reconstructing their vocal tracts, Quam says. 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.
But, says Coleman, the model Quam and colleagues used to reconstruct
the ear requires researchers to input many different variables —
including characteristics such as the elasticity of ligaments that are
no longer present in the fossils. “You kind of have to make some
assumptions, and I worry that at some point the assumptions of the
models are going to break down.”
If H. heidelbergensis did have modern hearing capacity, however, it’s
logical to assume they had a primitive form of human communication, he
adds. Though it’s possible that H. heidelbergensis could hear in that
frequency range but didn’t use that ability for anything special,
“sensory systems are extremely neurologically expensive,” Coleman
says. It’s unlikely that the body would invest the resources in
maintaining such a system if it didn’t serve a purpose, he says.
The research comes on the heels of an April Molecular Biology and
Evolution study showing that Neandertals had two genes that are
similar to those implicated in language development in humans but
differ from those in chimpanzees.
http://www.sciencenews.org/view/generic/id/33933/title/Loud_and_clear
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