Researchers have found fossils of early human ancestors from a whopping 2 million years ago. These fossils offer information about the hearing of human ancestors at a time when they were becoming more like humans and less like chimps.
The study was published in Science Advances and involves two species found in South Africa. The two species are Australopithecus africanus and Paranthropus robustus.
Research showed that both of these had better hearing than both chimps and humans in frequency ranges that likely facilitated communication through vocals.
Both of the two species had a mix of ape-like and human-like hearing traits, and they lived in grassy ecosystems with trees and shrubs that were widely spaced, rather than in forests. They did, however, retreat to the forest, which would have been necessary to avoid being on the menu for the range of predators that would have existed at the time.
Their hearing was particularly sensitive in much higher frequencies than chimpanzees, and they both had better hearing than humans in the 1.5 to 3.5 kilohertz (kHz) range of frequencies.
"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," said Rolf Quam, from Binghamton University in New York.
The human species, or Homo sapiens, is distinct from other primates in that it has improved hearing across a wide range of frequencies, from around 1 to 6 kHz, where most sounds from spoken language lie.
It's important to note, however, that the early humans analyzed in the study did not have language, and their smaller brains and cranial anatomy did not give them the capacity to conceive of language. They did, however, communicate verbally.
