(see Popper and Fay, 1997). (It sho

(see Popper and Fay, 1997). (It should be noted that the
term `¢shes' includes modern bony ¢shes, elasmobranchs
(sharks and rays), as well as the jawless hag¢sh
and lampreys. However, due to limited data for groups
other than bony ¢shes, it is not clear where some of the
characteristics and hearing capabilities discussed herein
actually arose.) In some cases the similarity in function
is mediated by some of the basic auditory structures
(e.g., the sensory hair cell) that evolved very early in
vertebrate history. However, in other cases similar tasks
and functions have been accomplished in the auditory
system using diverse structures and mechanisms.
The theme we present here is that there may be a set
of very general and constant pressures that have shaped
the functions of auditory systems throughout vertebrate
evolution. The general factor may be a capacity for a
sort of auditory scene analysis (Bregman, 1990) that we
assume to have been important throughout the evolution
of vertebrate hearing. In this review we concentrate
on hearing mechanisms of ¢shes because these vertebrates
illustrate functions and functional relationships
in the auditory system that tend to be widely shared
among vertebrates. There are also instances where the
same basic structures are found throughout the vertebrates
and provide the basis for many of the shared
functions of the auditory system.