Research into human fossils
dating back to approximately two million years ago reveals that the hearing
pattern resembles chimpanzees, but with some slight differences in the
direction of humans.
The study relied on the use of CT scans and virtual computer
reconstructions to study the internal anatomy of the ear. The results suggest
that the early hominin species Australopithecus
africanus and Paranthropus robustus,
both of which lived around 2 million years ago, had hearing abilities similar
to a chimpanzee, but with some slight differences in the direction of humans.
Humans are distinct from most
other primates, including chimpanzees, in having better hearing across a wider
range of frequencies. Within this same frequency range, which encompasses many
of the sounds emitted during spoken language, chimpanzees and most other
primates lose sensitivity compared to humans.
In the South African fossils,
the region of maximum hearing sensitivity was shifted towards slightly higher
frequencies compared with chimpanzees, and the early hominins showed better
hearing than either chimpanzees or humans. It turns out that this auditory
pattern may have been particularly favorable for living on the savanna. In more
open environments, sound waves don't travel as far as in the rainforest canopy,
so short range communication is favored on the savanna.
The emergence of language is
one of the most hotly debated questions in paleoanthropology. There is a
general consensus among anthropologists that the small brain size and ape-like
cranial anatomy and vocal tract in these early hominins indicates they likely
did not have the capacity for language.
How do these results compare
with the discovery of a new hominin species, Homo naledi, announced just two
weeks ago from a different site in South Africa?
It is obvious that this
research is going to be a big step in anthropology and also in other sciences
as medicine, because it may help in understanding the different patterns of
audition and how and why have they evolved in this direction and not in another
one.
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