Whales learn to hear underwater
The jaw becomes an ear: sound travels through a fat-filled channel in the mandible to an isolated ear bone.
- When
- —
- Duration
- 10 million years
- Known to
- ± 2 million years
- Era
- Eocene, Cenozoic
Hearing in air and hearing in water are different engineering problems, because water carries sound into the body directly instead of stopping at the eardrum. Cetaceans solve it by isolating the ear region from the skull with air sinuses and routing sound through a fat body in a hollow lower jaw. The archaeocete series records the steps: Pakicetus has the dense involucrum but still hears mostly in air, Ambulocetus can pick up ground vibration through its jaw, and by the basilosaurids the fully aquatic arrangement is in place, ready for echolocation later.