Early humans were different from us in many ways, and a new discovery shows that it may have had a lot to do with the environment they lived in. According to a report from Discovery News, a new study reveals how our prehistoric ancestors communicated with each other based off of a tiny fossil discovered in South Africa.

The study, published in the journal Science Advances, found that our ancestors living in South Africa roughly 2 million years ago had a high sensitivity to close-range sounds. Researchers believe that these early hominids were able to hear sound better than both modern-day humans and chimpanzees.

The study’s lead author, Rolf Quam of Binghamton University, explained that Australopithecus africanus and Paranthropus robustus likely had an increased sensitivity to sounds between 1.0 and 3.0 kHz compared to chimps and modern humans. Quam also mentioned that early humans could pick up sounds that were softer than our ears can detect.

Quam and his team of researchers made the discovery after they built a model of the two species of early humans’ inner ears. They used CT scans and virtual models based on fossils that had been discovered by archaeologists. They chose the two species featured in the study because there was ample information about their internal anatomy, and many remains included ear bones that were left intact.

Being able to hear sounds at a short range with a heightened sensitivity likely had many evolutionary benefits for our ancestors. Previous studies examining the tooth enamel of prehistoric humans revealed that they likely consumed foods from both the forest and the savannah, suggesting that our early hominid ancestors from South Africa could split their time between these two different environments.

Humans likely sought refuge in the forests from predatory animals like leopards, lions, or hyenas.

Given the size of the cranial cavity and thus the size of the brain of many early hominids, researchers believe that they probably hadn’t developed the capacity for language. Their vocal tracts also lead researchers to believe that these hominids hadn’t quite figured out how to express themselves with words just yet.

That doesn’t mean they were silent, however. Like many other primates past and present, these hominids likely communicated thought vowel-based calls and grunts. Quam and his team believe there were also sounds that could help these vowels take meaning, called voiceless consonants.

According to Quam, “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.’ These are considered ‘voiceless consonants’ because the vocal chords do not move when they are produced.”
Researchers believe that human speech likely evolved to become more complex when hominids began adding these consonant sounds. Quam noted that humans were unique among other animals for our communication system that combines both of these sounds for added complexity. Our earliest ancestors likely also communicated nonverbally, using gestures and facial expressions just as much as they used sounds to alert others of danger or to show them the way somewhere. Given the sensitivity of their ears to sounds at close ranges, these early hominids also likely used whispering to get sensitive information across.

Jeffrey Schwartz, a professor in the Departments of Anthropology, History and Philosophy of Science from the University of Pittsburgh explains, “This amazingly interesting and intriguing study clearly adds a new dimension to the study of hominin sociality and behavior.” The professor supports the findings of the study, agreeing that the earliest humans in South Africa likely had a sense of hearing that differs from our own and from that of our closest living primate relatives.

So if the earliest humans heard sound in a radically different way from us, is our hearing going to change over the next two million years? Probably not, Quam predicts. “It is unlikely that our hearing pattern will change much in the future,” he said. “Our previous studies have shown that human fossils that date to around 430,000 years ago from northern Spain, and which represent ancestors of the later-in-time Neanderthals, had a hearing pattern almost identical to our own.” Perhaps as technology improves, humans’ inner ear anatomy will shift to pick up different frequencies. But for now, we’re stuck with these ears for the long run.