The Lost Ability to Swivel Our Ears

A Study Reveals the Vestigial Function of Ear Muscles

Tens of millions of years ago, our ancestors could swivel their ears to pick up sounds, much like cats and dogs do today. Humans lost that ability over time, and the muscles that once controlled ear movement are now mostly useless—except for a few people who can still wiggle their ears. However, new research suggests that these muscles still react when we listen intently, hinting at their primordial function.

Researchers Discover the Auricular Muscles’ Role in Listening

Researchers in Germany and the U.S. found that the muscles once used to move our ears, known as auricular muscles, still activate when we focus on competing sounds, as if trying to revive our distant ancestors’ ability to swivel or prick our ears. Although it’s unclear if this improves our hearing abilities today, their research indicates that the harder we try to listen, the more we engage those muscles.

The Study’s Findings

Andreas Schröer of Saarland University, who led the study, explained that there are three large muscles that connect the auricle to the skull and scalp and are important for ear wiggling. These muscles, particularly the superior auricular muscle, exhibit increased activity during effortful listening tasks. This suggests that these muscles are engaged not merely as a reflex but potentially as part of an attentional effort mechanism, especially in challenging auditory environments.

Previous Research and the Study’s Methodology

Previous research had already linked activity in the posterior and superior auricular muscles to attentive listening, suggesting that our primate ancestors used them to move their ear shells and funnel sounds to their eardrums. Schröer and his colleagues wanted to determine whether the muscles were more active when people had to listen harder. To achieve this, they attached electrodes to the auricular muscles of 20 participants without hearing problems and instructed them to listen to an audiobook emitted from speakers.

The Results

The researchers observed that the posterior and superior auricular muscles displayed different activity depending on the acoustic situation. The more effort participants exerted to hear the audiobook, the more the superior auricular muscles contracted. Additionally, when the audiobook played behind the participant, the participants’ posterior auricular muscles activated in a way that might have pointed their ears in that direction, if we still had that ability.

The Evolutionary History of the Auricular Muscles

The exact reason these muscles became vestigial is difficult to tell, as our ancestors lost this ability about 25 million years ago. 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.

Practical Applications of the Study

Ultimately, it seems like the superior auricular muscles reacted to how difficult the listening task was—activating more during the hardest listening tasks—whereas the posterior auricular muscles were triggered by the direction of the sound. Although the researchers admit that further research in more realistic conditions must confirm their results, superior auricular muscle activity could potentially serve as a physical indicator of listening effort.

Conclusion

So, the next time someone demands, "Are you listening?" watch out—they might soon have the tools to verify your answer. The study’s findings shed light on a vestigial part of our body—and a once-useful ability lost to evolution.