Evolution’s Ear
Recent changes in hearing-related genes may have influenced language development
By Bruce Bower
Imagine, for a moment, that you are smaller than a speck of dust and in the mood for some teeny-tiny sightseeing. It’s a perfect opportunity to take a scenic trip to the inner ear.
First, stroll up the ear canal. This is a fantasy, so no waxy buildup blocks the way. At the end of the fleshy tunnel, squeeze around the huge, circular membrane better known as the eardrum. Gingerly sidestep the precariously balanced, oddly shaped middle ear bones and proceed into the inner ear. Up ahead, rising like skyscrapers from a flat landscape, looms a cluster of stereocilia. These slender, interconnected projections sit atop the basic sensory elements of hearing — the inner ear hair cells. Bundles of gently waving stereocilia serve as receptacles for sound waves delivered from hair cells, transforming those waves into electrical signals that travel to the brain to be interpreted.
But the inner ear is more than just the mediator of hearing. As a core player in the human system for receiving and creating spoken language, it’s a hotbed of recent evolutionary change as well.