The spiral secrets of mammals? hearing abilities Whispering
galleries are curious features of circular buildings. As
whispers travel along the buildings’ curved walls, they remain
loud enough to be heard clearly on the other end of even a large
room. New research suggests we all carry a couple of them around
in our heads. Inside their inner ears, mammals (but not other
animals) have cochleas—coiled shell-like tubes in which incoming
sound energy tilts sensory hairs, generating electric signals to
the brain. Scientists thought coiled cochleas evolved as a way
to pack a longer tube length into the available skull space,
giving mammals better low-frequency hearing than other
vertebrates, which lack cochleas. To test the idea, Darlene
Ketten, a biologist at Woods Hole Oceanographic Institution
(WHOI), and WHOI researcher Julie Arruda provided high-
resolution CT scans, taken at the WHOI Computerized Scanning and
Imaging Facility, of cochleas from 13 different land and marine
mammal species. They included creatures