You won’t notice it, but when you listen hard enough, your ears — or at least the muscles around them — spring into action. Though (most) humans lost the ability to wiggle their ears millions of years ago, a new study reveals that vestigial muscles in our ears still twitch when we strain to listen. This faint echo of our evolutionary past suggests that our brains retain an ancient system for orienting toward sounds, even if it no longer serves a practical purpose.
Scientists call this feature a “neural fossil”. It’s a remnant of a system that once helped our ancestors pinpoint the direction of rustling leaves or approaching predators. Today, these muscles barely move, but they still activate when we focus on competing sounds, offering a fascinating glimpse into how evolution leaves its mark on our bodies.
A Vestigial System Still Trying to Help
Many animals move their ears — and it’s very useful. Cats, dogs, and deer, for example, can swivel their ears to focus on specific sounds. But humans lost this ability around 25 million years ago, as our ancestors became more reliant on vision and complex vocal communication. The muscles responsible for ear movement — known as the auricular muscles — became vestigial. Now they linger in our bodies as evolutionary relics. Other vestigial features in the human body include sinuses, the tailbone, and wisdom teeth.
Yet, these ear muscles aren’t entirely dormant. Researchers from Saarland University in Germany found that they activate when people listen hard, especially in noisy environments.
“These muscles, particularly the superior auricular muscle, exhibit increased activity during effortful listening tasks,” said Andreas Schröer, the study’s lead author. “This suggests that they are engaged not merely as a reflex but potentially as part of an attentional effort mechanism.”
To test this, Schröer and his team recruited 20 participants with normal hearing. They placed electrodes on the participants’ auricular muscles and played an audiobook alongside distracting podcasts. The scenarios ranged from easy (a quiet podcast with a distinct pitch) to difficult (a loud, pitch-similar podcast competing with the audiobook). Participants rated their listening effort and were quizzed on the audiobook’s content.
The results were striking. The superior auricular muscles, which lift the ear upward and outward, became more active as the listening task grew harder. Meanwhile, the posterior auricular muscles, which pull the ear backward, responded to sounds coming from behind the listener.
“The ear movements that could be generated by the signals we have recorded are so minuscule — or even absent — that there is probably no perceivable benefit,” Schröer said. “So, we think that this vestigial auriculomotor system is ‘trying its best,’ but probably doesn’t achieve much.”
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What This Means for Hearing and Evolution
While activating these muscles doesn’t seem to improve hearing, it may provide an objective measure of listening effort. This could be useful for diagnosing hearing difficulties or designing better hearing aids. “Investigating the possible effects of muscle strain itself or the ear’s minuscule movements on the transmission of sound is something we want to do in the future,” Schröer said.
The findings also highlight how evolution repurposes or preserves ancient systems. “The exact reason these became vestigial is difficult to tell,” Schröer noted. “One possible explanation could be that the evolutionary pressure to move the ears ceased because we became much more proficient with our visual and vocal systems.”
Still, the study is just a starting point. With only 20 participants, all of whom had normal hearing, the results need to be confirmed in larger, more diverse groups. Future research could explore whether these muscles play a role in people with hearing impairments. We may also study how the muscles interact with other aspects of auditory processing.
Even as we navigate a world of smartphones and streaming audio, our ears still carry traces of a time when listening hard could mean the difference between life and death. Yet, in its faint twitches, we can hear the whispers of our distant past.
The findings appeared in the journal Frontiers in Neuroscience.
