New York Times. Haaretz, news and voila!
A sophisticated audio system, which produces sounds in a frequency range of up to 20 Hz, may be the perfect tool for playing music, but you don't need such improved sound quality to understand speech. The human ear is content with a much more limited frequency range. It is sensitive to frequencies of 4,000-2,000 Hz, a range that includes many of the sounds unique to human speech.
In the eyes of human evolution researchers, this range of sensitivity is related to the development of spoken language. Studies have shown that the optimal hearing frequencies of chimpanzees, for example, are 8,000-1,000 Hz. The increased sensitivity of humans to intermediate frequencies can, therefore, be seen as an evolutionary adaptation to speech. The question is, at what stage in human development did this adaptation occur.
Some clues that could lead to the answer were provided by a team of Spanish scientists, who studied human fossils from 350 thousand years ago. The researchers delved into the structure of the outer and middle ear of the human species Homo heidelbergensis in fossils found in the Sierra de Atapuerca, an archaeological site near Burgos in Spain.
In the first step, they accurately measured the anatomical characteristics of the ear, including details such as the diameter of the auditory canal. Later, while using a technique common in this type of research, they built an electrical circuit that simulated the way sound is transmitted in the ear. This model allowed them to determine which frequencies the ear is particularly sensitive to.
The results, reported in the current issue of the journal "Sciences of the National Academy of Proceedings", revealed that this human species had great sensitivity to a frequency range of up to 5,000 Hz, similar to that of modern humans. The researchers therefore hypothesize that the ear was adapted to receiving speech already 350 thousand years ago.
Henry Fontaine, New York Times, Haaretz, Walla!
With the approval of Walla
