Two million-year-old fossils revealed early humans ancestors' hearing patterns were similar to that of modern chimpanzees.
A team of scientists performed CT scans and virtual computer reconstruction on several fossil hominins discovered in South Africa to gain insight into ancient ear anatomy, Binghamton University reported. The findings suggest the early hominin species Australopithecus africanus and Paranthropus robustus had similar hearing systems to chimpanzees, but with some differences that resembled what is seen in today's humans. Humans have better hearing across a wider range of frequencies than most modern primates, which is believed to allow us to comprehend languages.
"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 Rolf Quam, assistant professor of anthropology at Binghamton University. "So we were interested in finding out when this human-like hearing pattern first emerged during our evolutionary history."
Past studies have show 430,000-year-old Sima hominins (later Neanderthals) had identical hearing patterns to modern day humans, but the earlier South African specimens have now been shown to have had much more primitive hearing. The region of maximum hearing sensitivity was shifted towards higher frequencies than chimpanzees', and their hearing between the ranges of 1.0 and 3.0 kHz was better than what is seen in either chimpanzees or humans. This unique auditory pattern may have helped the ancient human ancestors thrive in open Savannas where sound waves don't travel as far as they do in more crowded environments.
"We know these species regularly occupied the savanna since their diet included up to 50 percent of resources found in open environments" Quam said. The researchers argue that this combination of auditory features may have favored short-range communication in open environments.
The researchers noted that they do not believe the findings indicate these early humans had a fully developed spoken language. Scientists have generally agreed "small brain size and ape-like cranial anatomy and vocal tract" suggest these early beings did not have a capacity for language.
"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," Quam said.
The study was published in a recent edition of the journal Science Advances.
