Ancient auditory illusions reflected in prehistoric art?

Here are prehistoric paintings of hoofed animals in a cave with thunderous reverberations located in Bhimbetka, India. Credit: S. Waller

During the 168th Meeting of the Acoustical Society of America (ASA), to be held October 27-31, 2014 at the Indianapolis Marriott Downtown Hotel, Steven J. Waller, of Rock Art Acoustics, will describe several ways virtual sound images and absorbers can appear supernatural.

"Ancient mythology explained echoes from the mouths of caves as replies from spirits, so our ancestors may have made cave paintings in response to these echoes and their belief that echo spirits inhabited rocky places such as caves or canyons," explained Waller.

Just as light reflection gives an illusion of seeing yourself duplicated in a mirror, sound waves reflecting off a surface are mathematically identical to sound waves emanating from a virtual sound source behind a reflecting plane such as a large cliff face. "This can result in an auditory illusion of somebody answering you from within the rock," Waller said.

Echoes of clapping can sound similar to hoof beats, as Waller pointed out, while multiple echoes within a cavern can blur together into a thunderous reverberation that mimics the sound of a herd of stampeding hoofed animals.

"Many ancient cultures attributed thunder in the sky to 'hoofed thunder gods,' so it makes sense that the reverberation within the caves was interpreted as thunder and inspired paintings of those same hoofed thunder gods on cave walls," said Waller. "This theory is supported by acoustic measurements, which show statistically significant correspondence between the rock art sites and locations with the strongest sound reflection."

Other acoustical characteristics may have also been misinterpreted by ancient cultures unaware of sound wave theory. Waller noticed a resemblance between an interference pattern and Stonehenge, so he set up an interference pattern in an open field with just two flutes "droning the same note" to explore what it would sound like.

"The quiet regions of destructive sound wave cancellation, in which the high pressure from one flute cancelled the low pressure from the other flute, gave blindfolded subjects the illusion of a giant ring of rocks or 'pillars' casting acoustic shadows," Waller said.

He traveled to England and demonstrated that Stonehenge does indeed radiate acoustic shadows that recreate the same pattern as interference. "My theory that musical interference patterns served as blueprints for megalithic stone circles -- many of which are called Pipers' Stones -- is supported by ancient legends of two magic pipers who enticed maidens to dance in a circle and turned them all into stones," Waller noted.

There are several important implications of Waller's research. Perhaps most significantly, it demonstrates that acoustical phenomena were culturally significant to early humans -- leading to the immediate conclusion that the natural soundscapes of archaeological sites should be preserved in their natural state for further study and greater appreciation.

"Even today, sensory input can be used to manipulate perception and lead to illusions inconsistent with scientific reality, which could have interesting practical applications for virtual reality and special effects in entertainment media," Waller said. "Objectivity is questionable, because a given set of data can be used to support multiple conclusions."

The history of humanity is full of such misinterpretations, such as the visual illusion that the sun moves around the earth. "Sound, which is invisible and has complex properties, can easily lead to auditory illusions of the supernatural," he added. "This, in turn, leads to the more general question: what other illusions are we living under due to other phenomena that we are currently misinterpreting?"

Presentation #2aAA11, "Virtual sound images and virtual sound absorbers misinterpreted as supernatural objects," by Stephen J. Waller will take place on Tuesday, October 28, 2014. The abstract can be found by searching for the presentation number here: https://asa2014fall.abstractcentral.com/planner.jsp

Source:  Acoustical Society of America (ASA)

Oldest stone tool ever found in Turkey discovered

Stone tool approximately 1.2 million years old. Credit: Image courtesy of University of Royal Holloway London

Scientists have discovered the oldest recorded stone tool ever to be found in Turkey, revealing that humans passed through the gateway from Asia to Europe much earlier than previously thought, approximately 1.2 million years ago.

According to research published in the journal Quaternary Science Reviews, the chance find of a humanly-worked quartzite flake, in ancient deposits of the river Gediz, in western Turkey, provides a major new insight into when and how early humans dispersed out of Africa and Asia.

Researchers from Royal Holloway, University of London, together with an international team from the UK, Turkey and the Netherlands, used high-precision equipment to date the deposits of the ancient river meander, giving the first accurate timeframe for when humans occupied the area.

Professor Danielle Schreve, from the Department of Geography at Royal Holloway, said: "This discovery is critical for establishing the timing and route of early human dispersal into Europe. Our research suggests that the flake is the earliest securely-dated artefact from Turkey ever recorded and was dropped on the floodplain by an early hominin well over a million years ago."

The researchers used high-precision radioisotopic dating and palaeomagnetic measurements from lava flows, which both pre-date and post-date the meander, to establish that early humans were present in the area between approximately 1.24 million and 1.17 million years ago. Previously, the oldest hominin fossils in western Turkey were recovered in 2007 at Koçabas, but the dating of these and other stone tool finds were uncertain.

"The flake was an incredibly exciting find," Professor Schreve said. "I had been studying the sediments in the meander bend and my eye was drawn to a pinkish stone on the surface. When I turned it over for a better look, the features of a humanly-struck artefact were immediately apparent.

"By working together with geologists and dating specialists, we have been able to put a secure chronology to this find and shed new light on the behaviour of our most distant ancestors."

Source: University of Royal Holloway London

A kingdom of cave beetles found in Southern China

Credit: Mingyi Tian; CC-BY 4.0

A team of scientists specializing in cave biodiversity from the South China Agricultural University (Guangzhou) unearthed a treasure trove of rare blind cave beetles. The description of seven new species of underground Trechinae beetles, published in the open access journal ZooKeys, attests for the Du'an karst as the most diverse area for these cave dwellers in China.

"China is becoming more and more fascinating for those who study cave biodiversity, because it holds some of the most morphologically adapted cavernicolous animals in the world. This is specifically true for fishes and the threchine beetles, the second of which is also the group featured in this study," explains the senior author of the study Prof. Mingyi Tian.

Like most cavernicolous species, Trechinae cave beetles shows a number of specific adaptations, such as lack of eyes and colour, which are traits common among cave dwellers.

The new Trechinae beetles belong to the genus Dongodytes whose members are easily recognizable by their extraordinary slender and very elongated body. Members of this genus are usually very rare in caves, with only five species reported from China before now.

During the recent study of the cave systems in Du'an karst however this numbers drastically changed, Out of the 48 visited caves 12 held populations of trechine beetles. A total of 103 samples were collected, out of which the team of scientists determined ten different species, seven of which are new to science.

"This new discovery casts a new light on the importance of the Du'an Karst as a biological hotspot for cavernicolous Trechinae in China," adds Prof. Mingyi Tian.

Source: Pensoft Publishers