NATURE: Animal Ears Wax Eloquent

It's the ears of extinct pterosaurs and tiny flies that are creating a buzz with scientists. What may come out of them is a better picture of how ancient creatures lived, and a way to build a better hearing aid.

Traditional approaches to studying animal movement involved measuring limb proportions, muscle attachments, etc. The "guidance system," however, is the system of fluid-filled loops in the inner ear, which helps orient the brain, which in turn provides direction and balance. Studies of modern animals have demonstrated relationships between various inner ear configurations and animal lifestyles (agile gazelles have proportionately larger loops than do plodding hippos, for example).

In recent years, Witmer and other scientists have been studying the balance organs of pre-human ancestors and other long-gone animals, and therefore make better insights about how they interacted with their environments and with one another. Now, rather than destroying precious fossil skulls, scientists can use CT scans to peer inside and size up the balance organs (and brain regions) of extinct creatures.

As profiled in a recent issue of the journal Science, Witmer wondered about pterosaurs: How well did these enormous reptiles fly? How agile were they? How did they orient their bodies in flight? Based on his CT measurements, he has concluded that they had enormous inner ears and large sight lobes, which suggests they were agile flyers and eagle-eyed hunters.

Read the Science article about fossil ears on a Harvard University site [free], or at the journal's own site [fee required]

Visit researcher Witmer's home page

The problem the Ormia must solve is one that humans, too, must contend with – and especially humans with hearing aids: how to separate the signal (i.e. what we're interested in) from the noise (i.e. all the other, less interesting sounds mixed in the waves that are constantly bathing our ears).

Current hearing aids tend to amplify noise and distort the sound. According to a recent article in the New York Times, 80% of the people in the US who would benefit from aids do not use them, for precisely this issue. (And half of those who do are not satisfied.)

Miles is working to imitate the unique physical structure of Ormia's ear membranes to create a directionally sensitive – and very small – microphone, one that would reject noise not coming from the desired direction. He has fashioned three rocking silicon diaphragms onto a silicon chip the size of a pencil eraser. Developing compact and reliable ways to convert the waves to electrical signals is a challenge, but other teams are trying to adapt lasers and interferometers for the job, leading to commercialization.

Read the New York Times article, a profile about Miles from his university site, or an press release about a previous breakthrough in his research