Humans lost the ability to turn their ears, but these vestigial muscles still contract

Millions of millions of years ago, our ancestors could turn their ears to collect sounds, just like cats and dogs today. Humans lost that ability over time, and the muscles that once controlled the movement of the ear are now useless, except for some people who can still move their ears. But new research shows that these muscles still react when we listen carefully, hinting at their primary function.

Researchers in Germany and the United States found that the muscles once used to move our ears, known as headphones, are still activated when we focus on competitive sounds, as if trying to revive the ability of our distant ancestors to turn or click . Although it is not clear if this improves our auditory skills today, its research indicates that the more we try to listen, the more we involve those muscles. Excitedly, the findings also shed light on a vestigial part of our body, and an once useful skill lost by evolution.

“There are three large muscles that connect the atrium with the skull and scalp and are important for the organ,” said Andreas Schröer of the University of Saarland, who directed the study, in a journal statement Borders. “These muscles, particularly the upper atrial muscle, exhibit greater activity during effort listening tasks. This suggests that these muscles are committed not only as a reflection but potentially as part of an attentional effort mechanism, especially in challenging auditory environments. “

Previous investigations had already linked the activity in the posterior and upper atrial muscles (the largest atrial muscles) with a attentive listening, which suggests that our primates ancestors used them to move the shells of their ear and the channel sounds to his eardrums. However, Schröer and his colleagues wanted to determine if the muscles were more active when people had to listen stronger.

As detailed in a study Posted today in BordersThe researchers joined electrodes, devices that detect electrical impulses, to the atrial muscles of 20 participants without hearing problems, and told them to listen to an audiobook emitted from the speakers. The participants heard the audiobook at various levels of difficulty and made a questionnaire about their content at the end. Sometimes, researchers played a podcast that distracted at the same time, and occasionally the sounds come from different directions, but the task was always attainable, according to the researchers. If the participant surrendered because it was too difficult, the activity linked to the atrial muscle effort would cease.

Ultimately, the researchers observed that the posterior and higher atrial muscles showed a different activity depending on the acoustic situation. The more effort the participants were striving to listen to the audiobook, the more the upper atrial muscles were contracted. In addition, when the audiobook played behind the participant, the posterior headphones of the participants activated in a way that they could have pointed their ears in that direction, if we still had that ability.

“The exact reason why these (muscles) became vestigial is difficult to know, since our ancestors lost this ability about 25 million years ago,” Schröer explained. “A possible explanation could be that the evolutionary pressure to move the ears ceased because we became much more competent with our visual and vocal systems.”

Ultimately, it seems that the upper atrial muscles reacted to how difficult the listening task was, activating more during the most difficult listening tasks, while the posterior atrial muscles were triggered by the sound direction.

“The movements of the ear that could be generated by the signals that we have registered are so tiny that there is probably not a perceptible benefit,” Schröer added. “However, the atrium itself (the hell of the ear) contributes to our ability to locate the sounds. So, our atriculomotor system probably does the best that can be vestigial for 25 million years, but it can’t get much. “

What are the practical applications of these almost useless ear muscles? Although researchers admit that greater research in more realistic conditions must confirm its results, the upper atrial muscle activity could serve as a physical indicator of listening effort.

So next time someone demands Are you listening? Be careful, they can soon have the tools to verify your answer.