Some people can move their ears, while for others, this ability is elusive. This difference raises questions about the underlying anatomy and the reasons behind it. Understanding the muscles involved and their evolutionary history provides insights into this human trait.
The Muscles Behind Ear Movement
The muscles primarily responsible for ear movement are the auricular muscles, a group of three distinct muscles located around the outer ear. These include the anterior auricular muscle, which pulls the ear forward and upward; the superior auricular muscle, which lifts the ear upward and outward; and the posterior auricular muscle, which moves the ear backward and downward. These muscles are part of the broader group of facial muscles.
These auricular muscles connect the ear’s outer shell, the auricle or pinna, to the skull and scalp. Their function is directly controlled by branches of the facial nerve (cranial nerve VII). While present in everyone, these muscles are largely considered vestigial in humans, meaning they are remnants of structures that once served a more prominent purpose in our evolutionary ancestors. Recent research indicates that these muscles can still show activity, particularly during attentive listening.
Why People Differ in Ear Wiggling Ability
The ability to voluntarily wiggle one’s ears varies significantly among individuals, with only a small percentage able to do so consciously. This difference often relates to the degree of development of the auricular muscles and the strength of the neural pathways connecting them to the brain. For many, these muscles are underdeveloped, or the brain’s connection for voluntary control is weak, making conscious movement difficult or impossible.
While genetics play a role in the presence of these muscles, the ability to wiggle ears is not a simple inherited trait. Studies suggest that while some ear wigglers have parents with the same ability, cases exist where both parents lack the trait. This indicates that conscious control over these muscles may also involve a neurological training aspect. Some individuals can learn to move their ears through conscious practice, suggesting that the underlying muscles and nerves are present, and it’s the development of voluntary neural control that differs.
The Evolutionary Story of Ear Muscles
The presence of auricular muscles in humans, despite their limited function, tells a story of our evolutionary past. These muscles are considered vestigial structures, remnants from ancestors who relied on ear movement for survival. In many other mammals, such as dogs, cats, and horses, these muscles are well-developed and allow for precise ear swiveling. This ability helps them to direct their ears towards sounds, aiding in directional hearing, locating prey or predators, and even communicating.
Millions of years ago, our primate ancestors likely used these muscles to funnel sound more effectively, improving their ability to detect subtle noises. However, as humans evolved, developing upright posture, improved head mobility, and sophisticated visual and vocal communication systems, the need for mobile ears diminished. The auricular muscles became less functional, though they did not entirely disappear.