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And just as a ship is more stable the deeper it rides in the water, snakes often bury themselves in sand to make their hearing more precise. Buried, a snake can more easily detect the differences in the way its jaw moves. After a sound is picked up by a snake's jaw bones, it travels into the cochlea, where nerves pick up the signal and transmit it to the brain. By hearing through their jaw bone and through a traditional ear, snakes essentially evolved a second way to hear, say the researchers. Humans also have a very crude version of this ability. If you hit a tuning fork lightly and place it in the air next to your ear, the sound will be faint. If you lightly hit the tuning fork again and then place the base against the bone behind your ear, the sound becomes much stronger. While a human jaw is one complete bone, snakes actually have two jaws, an adaptation that allows them to swallow prey larger than themselves, but also apparently lets them hear in stereo. Catherine Carr, a biologist at the University of Maryland who was not involved in the research, said that the work "was truly interesting. Transmission through the skull may have been how the first land vertebrates heard." The work was reported recently in the journal Physical Review Letters.
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