Our Ancestors Heard the World Differently

Our ancestors apparently had a lot to say 2 million years ago, even if they said it quietly.

Early humans heard sounds differently than we do today, according to new research that provides intriguing clues on the environments our ancestors were living in, and how prehistoric humans communicated with each other.

A key finding of the study, published in the journal Science Advances, is that our ancestors living in South Africa around 2 million years ago were extremely sensitive to close-range sounds, hearing them more keenly than both our species and chimpanzees do now.

"We concluded that Australopithecus africanus and Paranthropus robustus had a heightened sensitivity to sound between 1.0-3.0 kHz compared with both chimpanzees and humans," lead author Rolf Quam, an assistant professor of anthropology at Binghamton University, told Discovery News.

Photos: Faces of Our Ancestors

He added that these early humans "were capable of hearing softer sounds" than our species and chimps can.

Quam and colleagues made the determination after reconstructing the internal anatomy of the ears of the two prehistoric humans. To do so, the researchers used CT scans and virtual computer reconstructions based on fossils. The particular human species were selected for the study because their remains include preserved ear bones.

The sensitivity to short-range sounds likely would have facilitated up close communication in an open habitat. Prior research on the tooth enamel of the prehistoric humans found evidence for consumption of foods found in both forests and savannahs, so our South African ancestors must have divided their time between these two environments.

Retreating to the forest might have been necessary, since humans were on the menu at the time for a wide range of large predators, such as leopards, lions and hyenas.

Photos: Early Humans Brought To Life In Exhibit

In terms of how the prehistoric humans would have been communicating with each other, there is a general consensus among anthropologists that the small brain size, ape-like cranial anatomy and vocal tract of these individuals would not have given them the capacity for language.

Like other primates, though, they would have been emitting meaningful vowel-based calls. Quam and his team propose also propose that they could have used what are known as "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," Quam explained. "These are considered 'voiceless consonants' because the vocal chords do not move when they are produced."

It is possible then that human speech evolved through the addition of these articulatory sounds to the vowel-based calls. Quam pointed out that humans are unique among animals in that our communication system relies heavily on the use of consonants, in addition to vowels.

Our ancestors were probably using a lot of visual communication as well, and might even have whispered, given their ability to hear close, quiet sounds so sharply.

First Humans Out of Africa Were Small, Scrappy

Jeffrey Schwartz, a professor in the Departments of Anthropology, History and Philosophy of Science at the University of Pittsburgh, told Discovery News that "this amazingly interesting and intriguing study...clearly adds a new dimension to the study of hominin (early human) sociality and behavior."

Schwartz agrees that early humans in South Africa likely did have a sense of hearing that was "non-sapiens," meaning that it was different than that of our species.

As for what human hearing will be like thousands of years from now, Quam made a prediction.

"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."

Recreation of Australopithecus Africans.

Back in the Beginning

To put a human face on our ancestors, scientists from the Senckenberg Research Institute used sophisticated methods to form 27 model heads based on tiny bone fragments, teeth and skulls collected from across the globe. The heads are on display for the first time together at the Senckenberg Natural History Museum in Frankfurt, Germany. This model is Sahelanthropus tchadensis, also nicknamed "Toumai," who lived 6.8 million years ago. Parts of its jaw bone and teeth were found nine years ago in the Djurab desert in Chad. It's one of the oldest hominid specimens ever found.

Australopithecus afarensis

With each new discovery, paleoanthropologists have to rewrite the origins of man's ancestors, adding on new branches and tracking when species split. This model was fashioned from pieces of a skull and jaw found among the remains of 17 pre-humans (nine adults, three adolescents and five children) which were discovered in the Afar Region of Ethiopia in 1975. The ape-man species, Australopithecus afarensis, is believed to have lived 3.2 million years ago. Several more bones from this species have been found in Ethiopia, including the famed "Lucy," a nearly complete A. afarensis skeleton found in Hadar.

Australopithecus africanus

Meet "Mrs. Ples," the popular nickname for the most complete skull of an Australopithecus africanus, unearthed in Sterkfontein, South Africa in 1947. It is believed she lived 2.5 million years ago (although the sex of the fossil is not entirely certain). Crystals found on her skull suggest that she died after falling into a chalk pit, which was later filled with sediment. A. africanus has long puzzled scientists because of its massive jaws and teeth, but they now believe the species' skull design was optimal for cracking nuts and seeds.

Paranthropus aethiopicus

The skull of this male adult was found on the western shore of Lake Turkana in Kenya in 1985. The shape of the mouth indicates that he had a strong bite and could chew plants. He is believed to have lived in 2.5 million years ago and is classified as Paranthropus aethiopicus. Much is still unknown about this species because so few reamins of P. aethiopicus have been found.

Paranthropus boisei

Researchers shaped this skull of "Zinj," found in 1959. The adult male lived 1.8 million years ago in the Olduvai Gorge of Tanzania. His scientific name is Paranthropus boisei, though he was originally called Zinjanthropus boisei -- hence the nickname. First discovered by anthropologist Mary Leakey, the well-preserved cranium has a small brain cavity. He would have eaten seeds, plants and roots which he probably dug with sticks or bones.

Homo rudolfensis

This model of a sub-human species -- Homo rudolfensis -- was made from bone fragments found in Koobi Fora, Kenya, in 1972. The adult male is believed to have lived about 1.8 million years ago. He used stone tools and ate meat and plants. H. Rudolfensis' distinctive features include a flatter, broader face and broader postcanine teeth, with more complex crowns and roots. He is also recognized as having a larger cranium than his contemporaries.

Homo ergaster

The almost perfectly preserved skeleton of the "Turkana Boy" is one of the most spectacular discoveries in paleoanthropology. Judging from his anatomy, scientists believe this Homo ergaster was a tall youth about 13 to 15 years old. According to research, the boy died beside a shallow river delta, where he was covered by alluvial sediments. Comparing the shape of the skull and teeth, H. ergaster had a similiar head structure to the Asian Homo erectus.

Homo heidelbergensis

This adult male, Homo heidelbergensis, was discovered in in Sima de los Huesos, Spain in 1993. Judging by the skull and cranium, scientists believe he probably died from a massive infection that caused a facial deformation. The model, shown here, does not include the deformity. This species is believed to be an ancestor of Neanderthals, as seen in the shape of his face. "Miquelon," the nickname of "Atapuerca 5", lived about 500,000 to 350,000 years ago and fossils of this species have been found in Italy, France and Greece.

Homo neanderthalensis

The "Old Man of La Chapelle" was recreated from the skull and jaw of a Homo neanderthalensis male found near La Chapelle-aux-Saints, in France in 1908. He lived 56,000 years ago. His relatively old age, thought to be between 40 to 50 years old, indicates he was well looked after by a clan. The old man's skeleton indicates he suffered from a number of afflictions, including arthritis, and had numerous broken bones. Scientists at first did not realize the age and afflicted state of this specimen when he was first discovered. This led them to incorrectly theorize that male Neanderthals were hunched over when they walked.

Homo floresiensis

The skull and jaw of this female "hobbit" was found in Liang Bua, Flores, Indonesia, in 2003. She was about 1 meter tall (about 3'3") and lived about 18,000 years ago. The discovery of her species, Homo floresiensis, brought into question the belief that Homo sapiens was the only form of mankind for the past 30,000 years. Scientists are still debating whether Homo floresiensis was its own species, or merely a group of diseased modern humans. Evidence is mounting that these small beings were, in fact, a distinct human species.

Homo sapiens

Bones can only tell us so much. Experts often assume or make educated guesses to fill in the gaps in mankind's family tree, and to develop a sense what our ancestors may have looked like. Judging from skull and mandible fragments found in a cave in Israel in 1969, this young female Homo sapien lived between 100,000 and 90,000 years ago. Her bones indicate she was about 20 years old. Her shattered skull was found among the remains of 20 others in a shallow grave.