Scientists have found two 2 million year old fossils of some early human ancestors. The skull includes the middle ear along with its three small bones that may help researchers figure out how the auditory system worked at the time when our species was beginning to hear like us, rather than like chimpanzees.
The study was published in the journal Science Advances. It involved two ape species, the Paranthropus robustus and Australopithecus africanus, which were both found from South Africa. Scientists found that the two animals had better hearing than both chimps and people, with a frequency range much higher than ours that probably helped them communicating more effectively.
The two species have both human and chimp-like anatomical traits. As opposed to the earliest human ancestors who prefered dense forests, these species inhabited ecosystems with fewer trees and spaced grasslands.
The hearing sensitivity of these species was much better than that of chimpanzees, particularly in the higher frequency range. Both species’ 1.0 to 3.0 khz range was far more advanced than ours. Rolf Quam, professor at the Binghamton University, NY, said that the majority of sounds included in that range are vowels and a couple of consonants.
Quam said that their auditory abilities may have been particularly useful in the savanna regions. He believes that because short range communication is more favorable in the savanna, because due to the open environments the sound waves do not travel as much as in the forests.
Quam adds that our ancestor’s hearing patterns started adapting to evolutionary changes about 3-2 million years ago, 3-4 million years after the human lineage started to evolve from chimpanzees.
In order for the scientists to understand the two species’ hearing characteristics, they have examined the fossils of the tiny bones which are found in the middle ear. These bones are also called ossicles, and they are: malleus, incus and staples. Researchers had created a virtual reconstruction of the species’ internal ear anatomy. Scientists say that these animals probably sounded quite strange, like a combination of chimps and humans simultaneously.
Our species is distinct from all other primates in that we have a better hearing range, covering frequencies from 1.0 to 6.0 khz. This range allows us to hear the vast majority of sounds that are emitted from speaking.
Scientists wanted to clear the air and added in the article that these ancestors of us did not had language, but rather they would communicate vocally as most primates to. Our species’ language emerged later in our evolutionary history, sometime after these two species existed.
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