2 million years ago, humans heard differently than we do today

In an interesting new study published in the journal Scientific Advances, researchers submit that humans from 2 million years ago heard differently than we do today.

“We know that the hearing patterns, or audiograms, in chimpanzees and humans are distinct because their hearing abilities have been measured in the laboratory in living subjects,” said lead author Rolf Quam of Binghamton University. “So we were interested in finding out when this human-like hearing pattern first emerged during our evolutionary history.”

An international group of researchers were able to reconstruct the internal anatomy of two ancient human ears by using CT scans and virtual computer reconstructions based on available fossils. Due to the limited number of fossilized skulls with intact inner ear bones, the researchers focused primarily on ancient humans native to South Africa.

“These fossil forms lived about two million years ago and represent early human ancestors. We took CT scans of the skulls. We created virtual reconstructions on the computer of the internal structures of the ear that will predict how an organism hears based on these measurements of its ear,” said Quam.

Scientists now believe that early humans were remarkably sensitive to close-range sounds- hearing even better than humans or chimpanzees do today. This enabled to sense predators lurking in the shadows. Or even to hear subtle warning signals from a fellow human.

“We concluded that Australopithecus africanus and Parathropus robustus had a heightened sensitivity to sound between 1.0-3.0 kHz compared with both chimpanzees and humans,” said Quam.

It is believed that this sensitivity also encouraged close communication. This would have helped them to avoid detection from the many predators in the area. These South African humanoids spent part of their time living in the open savannas and part of their time living in forests. Lions, leopards, and hyenas would all eat human if they had the chance.

Prehistoric humans most likely did not have a language like we do today. Rather, they communicated in a manner similar to other primates- using vowel-based calls and ‘voiceless consonants’.

“These are consonants that are produced solely by air flowing through the lips, teeth and tongue, such as the sounds in English associated with the letters “t,” “k,” “f” and “s,” said Quam. “These are considered ‘voiceless consonants’ because the vocal chords do not move when they are produced.”

“We feel our research line does have considerable potential to provide new insights into when the human hearing pattern emerged and, by extension, when we developed language,” said Quam.

And just how do these results match up to the hearing abilities of the newly discovered hominid species, Homo naledi, also from South Africa?

“It would be really interesting to study the hearing pattern in this new species,” said Quam. “Stay tuned.”



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